AN    OLD    DUTCH    WINDMILL    AND    A    MODERN    FRENCH    AEROPLANE 

This  Photograph  Protected  by  International  Copyright 


PRACTICAL  AERONAUTICS 


AN  UNDERSTANDABLE  PRESENTATION  OF 

INTERESTING  AND  ESSENTIAL  FACTS 

IN  AERONAUTICAL  SCIENCE 


By 

CHARLES  B.  HAYWARD 

• 

MEMBER,    SOCIETY   OF   AUTOMOBILE    ENGINEERS;    MEMBER,  THE    AERONAUTICAL 

SOCIETY;  FORMERLY  SECRETARY,  SOCIETY  OF  AUTOMOBILE  ENGINEERS; 
FORMERLY  ENGINEERING  EDITOR,  THE  AUTOMOBILE 

WITH  INTRODUCTION  BY 
ORVILLE     WRIGHT 

I 


ILLUSTRATED 


CHICAGO 

AMERICAN  SCHOOL  OF  CORRESPONDENCE 
1912 


COPYRIGHT  1912  BY 
AMERICAN  SCHOOL  OP  CORRESPONDENCE 


Entered  at  Stationers'  Hall,  London 
All  Rights  Reserved 


CONTENTS 


The  page  numbers  of  this  volume  will  be  found  at  the  bottom  of  the 
pages;  the  numbers  at  the  top  refer  only  to  the  section. 

DIRIGIBLE  BALLOONS 

INTRODUCTION  Page 

Early  attempts 1 

First  flying  machine 2 

Classification 2 

SIMPLE   BALLOONS 

Theory 3 

First  balloon 4 

Rozier 5 

Improvements  by  Charles 5 

Balloon  successful 5 

PROBLEMS   OF   THE   DIRIGIBLE 

Meusnier  the  pioneer 6 

Ability  to  float 8 

Air  resistance  vs.  speed 10 

Critical  size  of  bag 12 

Fabric  and  color 14 

Static  equilibrium 14 

Longitudinal  stability 15 

Dynamic  equilibrium 17 

Function  of  balloonets 18 

Location  of  propeller 23 

Relations  of  speed  and  radius  of  travel 25 

FRENCH   DIRIGIBLES 

First  Lebaudy 30 

Lebaudy  1904 30 

La  Patrie 31 

La  Republique  and  Le  Jaune 31 

Clement-Bayard  II 33 

Zodiac,  Le  Temps,  Astratorres 36 

Lieutenant  Selle  de  Beauchamp 37 

Note. — For  page  numbers  see  foot  of  pages. 


2636  Q 


CONTENTS 

GERMAN   DIRIGIBLES  Page 

Zeppelin  airships 38 

Parseval 49 

Parseval  sporting  type 49 

Gross : .  .  53 

Krell  1 53 

Veeh  I 55 

BRITISH   DIRIGIBLES 

Nulli  Secundus 57 

Mayfly 58 

AMERICAN   DIRIGIBLES 

United  States  War  balloon 58 

The  America 59 

Akron 72 

"Wire- Wound"  fabric 78 

ACHIEVEMENTS   OF   THE   DIRIGIBLE 

Wellman's  expedition 82 

Brucker's  proposed  expedition 89 

Carrying  passengers  by  airship 92 

Miscellaneous  exploits 95 


THEORY  OF  AVIATION 

EARLY   DAYS   OF   AVIATION 

Historical 99 

Langley's  experiments 104 

Wright  Brothers'  experiments 107 

United  States  Government  requirements 122 

Wilbur  Wright  in  Europe 124 

United  States  Government  requirements  fulfilled 124 

Aerial  experiment  association 126 

Herring-Curtiss  Company 129 

ELEMENTARY   AERODYNAMICS 

Air  resistance 130 

Air  pressure  on  moving  surfaces 133 

Ratio  of  lift  to  drift 136 

Aspect  ratio 138 

Skin  friction 140 

Center  of  pressure 140 

Evolution  of  curved  supporting  surface 141 

Note, — For  page  numbers  see  foot  of  pages. 


VI 


CONTENTS 

INTERNAL  WORK  OF  THE  WIND  Page 

Character  of  air  currents 143 

Movements  of  a  plane  in  wind , 143 

Air  holes 148 

Effect  of  eddies  and  waves 149 

Relative  speed  of  wind  and  aeroplane 150 

Certain  effects  on  the  wind 151 

GLIDING   AND   SOARING 

New  Wright  glider 154 

Montgomery's  gliding  experiments 159 

Early  observations  of  soaring 162 

Theory  of  soaring 166 

Conditions  for  continuous  soaring 167 

Aspiration 172 

MODERN   AERODYNAMIC   RESEARCH 

Aerodynamic  Institute  of  Kutchino 175 

Eiffel  aerodynamometric  laboratory 180 

Results  of  research  in  various  laboratories 187 

Methods  of  experimenting  on  test  surfaces 190 

Pressure  measuring  methods 192 

American  experimental  research 193 


TYPES   OF  AEROPLANES 

STANDARD   TYPES 

General  survey 197 

Nomenclature.  .1 .  198 

Wright  biplane 199 

Wright  racer 204 

Wright  Model  B  biplane 206 

Curtiss  biplane 214 

Voisin  biplane 219 

Voisin  tractor  screw  biplane 223 

Farman  biplane 227 

Sommer  biplane 231 

Cody  biplane 235 

Antoinette  monoplane 238 

Santos-Dumont  monoplane 242 

Bleriot  XI  monoplane 247 

Bleriot  XII  monoplane 250 

Grade  monoplane 251 

Pelterie  monoplane 255 

Pfitzner  monoplane 257 

Note. — For  page  numbers  see  foot  of  pages. 


VJl 


CONTENTS 

COMPARISON   OF   STANDARD   TYPES  Page 

Transverse  control 261 

Aspect  ratio 262 

Incident  angle 263 

Propellers 264 

Rudders 265 

Keels 267 

Mounting 267 

Speed 270 

Flight. 270 

Efficiency 273 

SPECIAL   TYPES 

Paulhan  trussed  type 275 

Nieuport  monoplane 278 

Bleriot  Limousine 282 

Tatin-Paulhan  aerial  torpedo 283 

Bleriot  racer 284 

Bleriot  Canard 284 

Antoinette  armored  monoplane 285 

Short  two-motor  biplane 287 

Dunne  biplane 288 

De  Marcay-Mooney  monoplane 291 

Variable  speed  aeroplanes 292 

Etrich  bird-wing  monoplane 295 

Queen-Martin  biplane 298 

Albatross  biplane 301 

Breguet  biplane 301 

Tubavion  monoplane 302 

Morane  monoplane 302 

Deperdussin  monoplane 303 

Valkyrie  monoplane 305 

Hanriot  monoplane 305 

Curtiss  racing  machine 306 

Multiplanes 308 

Steel  tube  construction 314 

Types  with  fixed  stabilizing  plane 318 

HYDROAEROPLANES 

Advantages 322 

Early  attempts 323 

Fabre  hydroaeroplane 324 

Curtiss  hydroaeroplane 328 

Burgess  hydroaeroplane 336 

Brown  hydroaeroplane 337 

Detroit  Flying  Fish 338 

Transatlantic  hydroaeroplane 339 

Note. — For  page  numbers  see  foot  of  pages. 


viii 


CONTENTS 

AERONAUTICAL   MOTOR 

GENERAL   MOTOR   REQUIREMENTS  Page 

Automobile  vs.  aeronautical  motor 348 

Fundamental  features  of  design 349 

Standard  forms 352 

AMERICAN   MOTOR   TYPES 

Wright 363 

Curtiss 366 

Four-cylinder  water-cooled  type 368 

Horizontal-opposed  type 368 

Eight-cylinder  V-type 371 

Two-cycle  motors 372 

Rotary  type 373 

Weight  per  horse-power  hour 378 

FOREIGN   MOTOR   TYPES 

Horizontal-opposed  type 379 

Conventional  four-cylinder  type 381 

V-type 389 

Water-cooled  types 396 

Fan  and  star  types 396 

Gobron-Brille  X-form 406 

Gnome  revolving-cylinder  type 408 

AERIAL   PROPELLER 

DESIGN   AND   CONSTRUCTION 

Factors  in  propeller  action 411 

Power  of  propellers 418 

Propeller  blades 421 

Propeller  construction 426 

Propeller  design 430 

Propeller  tests 434 

Number  of  propellers 437 

Location  of  propellers 439 

Propeller  efficiency 440 

AERONAUTICAL   PRACTICE 

STABILITY   OF   THE   AEROPLANE 

Variations  of  center  of  pressure 443 

Conditions  for  stability 444 

Methods  of  increasing  stability 445 

Methods  of  producing  effective  damping  couple 448 

Study  of  "center  of  pressure"  curves 450 

Longitudinal  and  lateral  stability 453 

Note. — For  page  numbers  see  foot  of  pages, 


ix 


CONTENTS 

AUTOMATIC   STABILITY  Page 

Air  reaction  principle 456 

Gravity  principle 460 

Eteve  stabilizer 465 

Gyroscopic  stabilizers 468 

Doutre  stabilizer 477 

Ellsworth  lateral  stabilizer. .                                                                          .  480 


ALTITUDE   AND   ITS   MEASUREMENT 

Altitude  records .  .  482 

Methods  of  altitude  measurement 485 

Individual  barograph  records 498 

Summary  of  altitude  records 500 

LEGAL   STATUS   OF   THE   ART 

Wright  patent  in  American  and  foreign  courts 505 

Legislation 524 

Customs..  .  526 


MILITARY   IMPORTANCE   OF   AEROPLANE   AND    DIRIGIBLE 

Attitude  of  military  powers 527 

Adaptability  to  war 531 

Operations  in  France 535 

Aeroplane  maneuvers  in  United  States 541, 

Italian  operations 547 

Guns  for  aerial  warfare. .  .  547 


WIRELESS   TELEGRAPHY   IN   AERONAUTICS 

Early  experiments  on  balloons 551 

Dangers  from  electric  discharge 553 

Preventive  methods 554 

Wireless  on  the  Zeppelins 556 

First  message  from  an  aeroplane 557 

Horton's  experiments 558 

Recent  aeroplane  records 559 

General  problems 562 


BUILDING   AND   FLYING   AN   AEROPLANE 

BUILDING  AEROPLANE   MODELS 

Model  with  rubber-band  motor 568 

Model  with  gasoline  motor 574 

Note. — For  page  numbers  see  foot  of  pages. 


CONTENTS 

BUILDING  A  GLIDER  Page 

Main  frame 577 

Glider  with  rudder  and  elevator , 581 

Learning  to  glide 581 

BUILDING  A   CURTISS   BIPLANE 

Cost 583 

General  specifications 584 

Main  planes  and  struts 594 

Making  turnbuckles  for  the  truss  wires 596 

Running  gear '. 597 

Outriggers 599 

Ailerons  for  lateral  stability 606 

Covering  of  the  planes 606 

Making  the  propeller 607 

Mounting  the  engine 614 

Controls 615 

Tests 617 

Assembling  the  biplane 617 


BUILDING   A   BLERIOT   MONOPLANE 

Motor 623 

Fuselage 626 

Truss  frame  built  on  fuselage 629 

Running  gear 630 

Wings 638 

Control  system 642 

Covering  the  planes 647 

Installation  of  mdtor 649 

New  features . .  .  650 


ART   OF   FLYING 

Methods  used  in  aviation  schools 654 

Use  of  the  elevating  plane 656 

Aeroplane  in  flight 657 

Center  of  gravity 657 

Center  of  pressure 660 

Ground  practice 660 

First  flight 661 

Warping  the  wings 662 

Making  a  turn 663 

Starting  and  landing 670 

Planning  a  flight 670 

Training  the  professional  aviator 671 

Note. — For  page  numbers  see  foot  of  pages. 


xi 


CONTENTS 

ACCIDENTS  AND   THEIR  LESSONS  Page 

Press  reports 672 

Fatal  accidents 674 

Causes 677 

Obstructions 677 

Stopping  of  motor 681 

Breakage  of  parts  of  aeroplanes 682 

Failure  of  control  mechanism 682 

Biplane  vs.  monoplane 684 

Record  breaking 686 

Excessive  lightness  of  machines 687 

Landings 688 

Lack  of  sufficient  motor  control 690 

Parachute  garment  as  a  safeguard 690 

Study  of  stresses  in  fancy  flying. . . , 691 

Methods  of  making  tests 694 

Increment  of  speed  in  driving 695 

Dirigible  accidents 696 

AMATEUR   AVIATORS 

Classes  of  amateurs 699 

Wright  and  Curtiss  patents 700 

AVIATION   AND   ITS   FUTURE 

DIRIGIBLE   VS.   AEROPLANE 

Dirigible 705 

Large  radius  of  action 709 

Aeroplane 709 

Recent  developments  in  dirigibles 713 

Refinement  of  details 715 

Air  pilots 716 

Air  harbors 717 

Improvements  of  design 719 

REWARDS   OF   AVIATION 

Prizes  for  flights 721 

Prizes  for  improvements -. 731 

Cost  of  equipment  and  maintenance 731 

AVIATION  RECORDS 

Early  records .*..... '. 733 

Records  for  1909  and  1910 735 

Records  for  1911 .  735 

Passenger  records 737 

Speed  records 739 

Note. — For  page  numbers  see  foot  of  pages. 


xii 


CONTENTS 

THE   FLYING   MACHINE   OF   THE   FUTURE        .  Page 

Unpromising  types 740 

Monoplane  vs.  biplane 745 

Improvements  in  construction 745 

Racing  machine  of  the  future 748 

Reefed  supporting  surfaces 750 

Duplicate  power  plant 752 

GLOSSARY 

INDEX 

Note. — For  page  numbers  see  foot  of  pages. 


INTRODUCTION 

THE  achievement  of  flight  by  man  after  ages  of  disappointment 
has  so  aroused  the  imagination  and  the  interest  of  the  public 
that  a  great  demand  has  been  created  for  works  treating  on  this 
subject.  A  number  of  authors  have  attempted  to  supply  this  demand. 
Some,  having  no  real  historical  or  scientific  knowledge  of  the  subject, 
have  been  compelled  to  draw  their  materials  from  the  imaginative 
stories  of  newspaper  writers.  Others,  with  some  knowledge  of  engi- 
neering and  physics  but  with  no  practical  experience  in  aeronautics, 
have  fallen  into  serious  errors  in  their  attempts  to  explain  the  prin- 
ciples of  flight.  This  has  resulted  in  the  publication  of  a  great  many 
works  that  might  better  have  been  left  unprinted. 

At  the  request  of  the  author  I  have  looked  over  some  of  the 
proofs  of  the  present  work.  On  account  of  lack  of  time  I  have  not 
been  able  to  read  all  the  chapters  as  I  should  like,  but  those  I  have 
examined,  such  as  the  chapters  treating  of  the  work  of  the  early 
experimenters  and  (the  present  status  of  the  patent  litigation,  are 
remarkably  free  from  the  errors  usually  found  in  aeronautical  works 
of  this  character.  The  story  of  the  early  work  of  my  brother  and 
myseff  is  also  correct,  and  is  taken  almost  verbatim  from  an  article 
written  by  us  several  years  ago  for  the  Century  Magazine.  The 
chapter  on  the  patent  litigation  is  the  best  and  clearest  presentation 
of  the  legal  aspect  of  the  subject  that  has  come  to  my  notice.  If 
the  portions  of  the  book  which  I  have  not  examined  have  been  pre- 
pared with  the  same  care  and  accuracy  as  those  I  have  read,  I  am 
sure  the  work  will  be  a  valuable  addition  to  the  literature  of  Aero- 
nautics. 


xv 


ONE    OF   THE   FRENCH    MILITARY   DIRIGIBLES    WITH   THE   BALLOON    SHED 

SHOWN   BELOW 


DIRIGIBLE  BALLOONS 


INTRODUCTION 

Of  the  first  attempts  of  men  to  emulate  the  flight  of  birds,  we 
have  no  knowledge,  but  one  of  the  earliest,  perhaps,  is  embodied 
in  the  myth  of  Icarus  and  Daedalus.  Xerxes,  it  is  said,  possessed 
a  throne  which  was  drawn  through  the  air  by  eagles.  The  Chinese 
have  sometimes  been  given  credit  for  the  invention  of  the  balloon, 
as  they  have  for  many  other  scien- 
tific discoveries.  It  is  related  that 
a  balloon  was  sent  up  at  Pekin  in 
celebration  of  the  ascension  of  the 
throne  by  an  emperor  in  the  be- 
ginning of  the  fourteenth  century. 

Early  Attempts.  Leonardo  da 
Vinci  devoted  some  time  to  the 
problem  of  artificial  flight.  His 
sketches  show  the  details  of  bat- 
like  wings  which  were  to  spread 
out  on  the  downward  stroke  and 
fold  up  with  the  upward  stroke. 
Francisco  de  Lana  planned  to  make 
a  flying  ship  the  appearance  of  which 
was  somewhat  like  that  shown  in 
Fig.  1,  by  exhausting  the  air  from 
metal  spheres  fastened  to  a  boat.  The  boat  was  to  be  equipped 
with  oars  and  sails  for  propulsion  and  guiding.  The  method  in  which 
he  purposed  to  create  the  vacuum  in  the  spheres  consisted  of  filling 
them  with  water,  thus  driving  out  the  air,  then  letting  the  water  run 
out.  He  thought  that  if  he  closed  the  tap  at  the  proper  time,  there 
would  be  neither  air  nor  water  in  the  spheres.  His  flying  ship  was 
never  constructed,  for  he  piously  decided  that  God  would  never 
permit  such  a  change  in  the  affairs  of  men. 

Copyright,  1912.  by  American  School  of  Correspondence. 


Fig.  1.     De  Lana  Airboat 


2  '  DIRIGIBLE   BALLOONS 

The  First  Flying  Machine.  In  1781,  Meerwein  of  Baden, 
Germany,  constructed  a  flying  machine,  and  was  the  first,  perhaps, 
to  intelligently  take  into  account  the  resistance  of  the  air.  He  took 
the  wild  duck  as  a  basis  of  calculation,  and  found  that  a  man  and 
machine  weighing  together  200  pounds  would  require-  a  wing  surface 
of  from  125  to  130  square  feet.  It  is  of  interest  to  note  that  Lilienthal, 
who  met  his  death  in  trying  to  apply  these  principles,  over  one  hun- 
dred years  later  found  these  figures  to  be  correct.  Two  views  of 
Meerwein's  apparatus  are  shown  in  Fig.  2.  The  construction  involved 
two  wood  frames  covered  with  cloth.  The  machine  weighed  56 
pounds  and  had  a  surface  area  of  111  square  feet.  The  operator 
was  fastened  in  the  middle  of  the  under  side  of  the  wings,  and  over 


Fig.  2.     Meerwein  Flying  Machine 

a  rod  by  which  he  worked  the  wings.  His  attempts  at  flight  were 
not  successful,  as  his  ideas  of  the  power  of  a  man  were  in  error. 

Classification.  All  attempts  at  human  flight  have  gone  to 
show  that  there  are  four  possible  ways  in  which  man  may  hope  to 
navigate  the  air.  He  may  imitate  the  flight  of  birds  with  a  machine 
with  moving  or  flapping  wings;  he  may  use  vertical  screws  or  helices 
to  pull  himself  up;  he  may  use  an  aeroplane  and  sail  the  air  like  an 
eagle;  or,  lastly,  he  may  raise  himself  by  means  of  a  gas  bag  and 
either  drift  with  the  wind  or  move  forward  by  means  of  propellers. 

In  these  attempts,  apparatus  of  several  different  types  has  been 
developed.  The  types  are  classed  in  two  general  divisions  based 
on  their  weight  relative  to  that  of  the  atmosphere,  viz,  the  lighter- 


DIRIGIBLE   BALLOONS  3 

than-air  machines  and  the  heavier-than-air  machines.  Lighter-than- 
air  machines  are  those  which  employ  a  bag  filled  with  a  gas  whose 
specific  gravity  is  sufficiently  less  than  that  of  the  air  to  lift  the  bag 
and  the  necessary  attachments  from  the  earth,  and  include  simple 
balloons  and  dirigibles.  Heavier-than-air  machines,  which  will 
neither  rise  nor  remain  in  the  air  without  motive  power,  include  all 
forms  of  aeroplanes. 

SIMPLE  BALLOONS 

Theory.  The  balloon-like  airship  has  been  more  highly  developed 
than  any  other  type  of  aerial  craft,  probably  because  it  offers  the 
most  obvious  means  of  overcoming  the  force  of  gravitation.  It 
depends  on  the  law  of  Archimedes: 

"Every  body  which  is  immersed  in  a  fluid  is  acted  upon  by  an 
upward  force,  exactly  equal  to  the  weight  of  the  fluid  displaced  by  the 
immersed  body." 

That  is,  a  body  will  be  at  rest  if  immersed  in  a  fluid  of  equal 
specific  gravity  or  equal  weight,  volume  for  volume;  if  the  body  has 
less  specific  gravity  than  the  fluid  in  which  it  is  immersed  it  will 
rise;  if  it  has  a  greater  specific  gravity  it  will  sink.  Therefore,  if 
the  total  weight  of  a  balloon  is  less  than  the  weight  of  all  the  air  it 
displaces  it  will  rise  in  the  air.  It  is,  then,  necessary  to  fill  the  balloon 
with  some  gas  whose  specific  gravity  is  enough  less  than  that  of  the 
air  to  make  the^  weight  of  the  gas  itself,  the  bags,  and  the  attach- 
ments, less  than  the  weight  of  the  air  displaced  by  the  whole  appa- 
ratus. The  gases  usually  employed  are  hydrogen,  coal  gas,  and  hot 
air. 

At  atmospheric  pressure  and  freezing  temperature,  the  weight 
of  a  cubic  foot  of  air  is  about  .08  pound;  the  weight  of  a  cubic  foot 
of  hydrogen  is  about  .005  pound,  under  the  same  conditions.  Accord- 
ing to  the  law  of  Archimedes,  a  cubic  foot  of  hydrogen  would  be 
acted  upon  by  a  force  equal  to  the  difference,  or  approximately  .075 
pound,  tending  to  move  it  upwards.  In  the  same  way,  a  cubic  foot 
of  coal  gas,  which  weighs  .04  pound,  would  be  acted  upon  by  an 
upward  force  of  .04  pound. 

It  is  evident,  then,  that  a  considerable  volume  of  gas  is  required 
to  lift  a  balloon  with  its  envelope,  net,  car,  and  other  attachments. 


DIRIGIBLE   BALLOONS 


Further,  it  requires  almost  twice  as  much  coal  gas  as  hydrogen, 
under  the  same  conditions,  for  we  have  seen  that  the  upward  force 
on  it  is  only  half  as  great.  The  lifting  power  of  hot  air  is  less  than 
one-eighth  as  great  as  that  of  hydrogen  at  the  highest  temperature 

that  can  possibly  be  used  in  a 
balloon. 

The  general  type  of  lighter- 
than-air  machines  may  be  divided 
into  aerostats  (ordinary  balloons, 
which  are  entirely  dependent  on 
wind  currents  for  lateral  move- 
ment, and  which  are  often  the 
chief  features  at  country  fairs) 
and  dirigible  balloons  or  aeronats 
(air  swimmers).  Dirigible  bal- 
loons employ  the  gas  bag  for 
maintaining  buoyancy,  and  have 
rudders  to  guide  them  and  pro- 
pellers to  drive  them  forward 
through  the  air  in  much  the 


Fig.  3.     Montgolfier  Balloon 


same  way  that  ships  are  driven 
through  the  water. 

The  First  Balloon.  For  several 
years,  Joseph  and  Steven  Mont- 
golfier had  been  experimenting 
with  a  view  to  constructing  a  bal- 
loon: in  the  first  place  by  filling 
bags  with  steam;  then  by  filling 
bags  with  smoke,  and  finally  by 
filling  bags  with  hydrogen.  These  attempts  were  all  failures,  for  the 
steam  rapidly  condensed  and  the  smoke  and  hydrogen  leaked  through 
the  pores  in  the  bags.  They  finally  hit  upon  the  idea  of  filling  the 
bag  with  hot  air,  by  means  of  a  fire  under  its  open  mouth.  Several 
balloons  were  burned  up,  but  the  next  was  always  made  larger,  until, 
at  their  first  public  exhibition  on  June  5,  1783,  the  bag  had  become 
over  35  feet  in  diameter.  On  this  occasion,  it  rose  to  a  height  of 
between  900  and  1,000  feet,  but  the  hot  air  was  gradually  escaping, 
and  at  the  end  of  ten  minutes  the  balloon  fell  to  the  ground. 


DIRIGIBLE   BALLOONS 


The  Montgolfiers  then  went  to  Paris,  where,  after  suffering 
the  loss  of  a  paper  balloon  by  rain,  they  sent  up  a  waterproofed  linen 
one  carrying  a  sheep,  a  duck,  and  a  rooster  in  a  basket.  A  rupture  in 
the  linen  caused  the  three  unwilling  aeronauts  to  make  a  landing 
at  the  end  of  about  ten  minutes.  The  Montgolfiers  received  great 
honor,  and  small  balloons  of  this  type  became  a  popular  fad.  One 
of  these  balloons  is  shown  in  Fig.  3,  making  an  ascension. 

Rozier.  The  first  man  to  go  up  in  a  balloon  was  Rozier,  who 
ascended  in  a  captive  balloon  to  a  height  of  about  80  feet,  in  the 
latter  part  of  the  year  1783.  Later,  in 
company  with  a  companion,  he  made  a 
voyage  in  a  free  balloon,  remaining  in  the 
air  about  half  an  hour.  In  these  balloons, 
the  air  within  was  kept  hot  by  means  of 
a  fire  carried  in  a  pan  immediately  below 
the  mouth  of  the  bag,  as  shown  in  Fig.  4. 
Accidents  were  numerous  on  account  of 
the  fabric  becoming  ignited  from  the  fire 
in  the  pan. 

Improvements  by  Charles.  The  phys- 
icist, Charles,  was  working  along  these  lines 
at  the  same  time.  He  coated  his  balloon 
with  a  rubber  solution  to  close  up  the 
pores,  and  was  thereby  enabled  to  sub- 
stitute hydrogen*  for  the  hot  air.  Shortly 

„         4.u      TVT  1C        >c  ur  u-u-"      Fig"  4"     Rozier  Hot-Air  Balloon 

aiter  the  Montgolners  nrst  public  exhibi- 
tion, Charles  sent  up  his  balloon  for  the  benefit  of  the  Academic  des 
Sciences  in  Paris.  The  balloon,  which  weighed  about  19  pounds, 
ascended  rapidly  in  the  air  and  disappeared  in  the  clouds,  where  it 
burst  and  fell  in  a  suburb  of  the  city.  The  impression  produced  upon 
the  peasants  at  seeing  it  fall  from  the  heavens  was  hardly  different 
from  what  could  be  expected.  They  believed  it  to  be  of  devilish  ori- 
gin, and  immediately  tore  it  into  shreds.  Charles  subsequently  built  a 
large  balloon  quite  similar  to  those  in  use  today.  A  net  was  used  to 
support  the  basket,  and  a  valve,  operated  by  means  of  ropes  from  the 
basket,  was  arranged  at  the  top  to  permit  the  gas  to  escape  as  desired. 
The  Balloon  Successful.  The  English  Channel  was  first  crossed 
in  1785.  Blanchard,  an  Englishman,  and  Jeffries,  an  American, 


6  DIRIGIBLE   BALLOONS 

started  from  Dover  on  January  7  in  a  balloon  equipped  with  wings 
and  oars.  After  a  very  hazardous  voyage,  during  which  they  had 
to  cast  overboard  everything  movable  to  keep  from  drowning,  they 
landed  in  triumph  on  the  French  coast. 

An  attempt  to  duplicate  this  feat  was  made  shortly  afterward  by 
Rozier.  He  constructed  a  balloon  filled  with  hydrogen,  below  which 
hung  a  receiver  in  which  air  could  be  heated.  He  hoped  to  replace 
by  the  hot  air  the  losses  due  to  leakage  of  hydrogen.  Soon  after  the 
start  the  balloon  exploded,  due  to  the  escaping  gas  reaching  the  fire, 
and  Rozier  and  his  companion  were  dashed  on  the  cliffs  and  killed. 

EARLY  DIRIGIBLES 

Meusnier  the  Pioneer.  The  fact  that  the  invention  of  the 
dirigible  balloon  and  means  of  navigating  it  were  almost  simultane- 
ous is  very  little  known  today  and  much  less  appreciated.  Like 
the  aeroplane,  its  development  was  very  much  retarded  by  the  lack 
of  suitable  means  of  propulsion,  and  the  actual  history  of  what  has 
been  accomplished  in  this  field  dates  back  only  to  the  initial  circular 
flight  of  La  France  in  1885.  Still  the  principles  upon  which  success 
has  been  achieved  were  laid  down  within  a  year  of  the  appearance 
of  Montgolfier's  first  gas  bag.  Lieutenant  Meusnier,  who  subse- 
quently became  a  general  in  the  French  army,  must  really  be  credited 
with  being  the  true  inventor  of  aerial  navigation.  At  a  time  when 
nothing  whatever  was  known  of  the  science,  Meusnier  had  the  dis- 
tinction of  elaborating  at  one  stroke  all  the  laws  governing  the 
stability  of  an  airship,  and  calculating  correctly  the  conditions  of 
equilibrium  for  an  elongated  balloon,  after  having  strikingly  demon- 
strated the  necessity  for  this  elongation.  This  was  in  1784  and  Meus- 
nier's  designs  and  calculations  are  still  preserved  in  the  engineering 
section  of  the  French  War  Office  in  the  form  of  drawings  and  tables. 

But  as  often  proved  to  be  the  case  in  other  fields  of  research, 
his  efforts  went  unheeded.  How  marvelous  the  establishment  of 
these  numerous  principles  by  one  man  in  a  short  time  really  is,  can 
be  appreciated  only  by  noting  the  painfully  slow  process  that  has 
been  necessary  to  again  determine  them,  one  by  one,  at  considerable 
intervals  and  after  numerous  failures.  Through  not  following  the 
lines  which  he  laid  down,  aerial  navigation  lost  a  century  in  futile 
groping  about;  in  experiments  absolutely  without  method  or  sequence. 


DIRIGIBLE  BALLOONS  7 

Meusnier's  designs  covered  two  dirigible  balloons  and  that  he 
fully  appreciated  the  necessity  for  size  is  shown  by  the  dimensions 
of  the  larger,  which  unfortunately  was  never  built.  This  was  to  be 
260  feet  long  by  130  feet  in  diameter,  in  the  form  of  an  ellipse,  the 
elongation  being  exactly  twice  the  diameter.  In  other  words,  a  perfect 
ellipsoid,  which  was  a  logical  and,  in  fact,  the  most  perfect  develop- 
ment of  the  spherical  form.  Although  increased  knowledge  of  wind 
resistance  and  the  importance  of  the  part  it  plays  has  proved  his 
relative  dimensions  to  be  faulty,  a  study  of  the  principal  features 


Fig.  5.      Meusnier  Dirigible  Balloon 

of  his  machine  shows  that  he  anticipated  the  present-day  dirigible 
of  the  most  successful  type  at  practically  every  point,  barring,  of 
course,  the  motive  power,  as  there  was  absolutely  nothing  available 
in  that  day  except  human  effort.  As  the  latter  weighs  more  than 
one-half  ton  per  horse-power,  it  goes  without  saying  that  Meusnier's 
balloon  would  have  been  dirigible  only  in  a  dead  calm. 

He  adopted  the  elongated  form,  conceived  the  girth  fastening, 
the  triangular  or  indeformable  suspension,  the  air  balloonet  and  its 
pumps,  and  the  screw  propeller,  all  of  which  are  to  be  found  in  the 
dirigibles  of  present-day  French  construction,  Fig.  5.  It  need  scarcely 


8  DIRIGIBLE   BALLOONS 

be  added  that  the  French  have  not  only  devoted  a  greater  amount 
of  time  and  effort  to  the  development  of  the  dirigible  than  any  other 
nation,  but  have  also  met  with  the  greatest  success  in  its  use.  It 
was  not  until  1886,  or  more  than  a  century  after  Meusnier  had  first 
elaborated  those  principles,  that  their  value  became  known.  They 
were  set  forth  by  Lieutenant  Letourne,  of  the  French  engineers,  in 
a  paper  presented  to  the  Academic  des  Sciences  by  General  Perrier. 
In  one  form  or  another,  the  salient  features  of  Meusnier's  diri- 
gible will  be  found  embodied  in  the  majority  of  attempts  of  later 
days.  His  large  airship  was  designed  to  consist  of  double  envelope, 
the  outer  container  of  which  was  to  provide  the  strength  necessary, 
and  it  was  accordingly  reinforced  by  bands.  The  inner  envelope  was 
to  provide  the  container  for  the  gas  and  was  not  called  upon  to  sup- 
port any  weight.  This  inner  bag  or  balloon  proper  was  designed 
to  be  only  partially  inflated  and  the  space  between  the  two  was  to  be 
occupied  by  air  which  could  be  forced  into  it  at  two  points  at  either 
end,  by  pumps,  so  as  to  maintain  the  pressure  on  the  gas  bag  uniform 
regardless  of  the  expansion  or  contraction  of  its  contents.  Here  in 
principle  was  the  air  balloonet  of  today.  Instead  of  employing  a  net 
to  hang  the  car  from  the  outer  envelope,  the  former  was  attached 
by  means  of  a  triangular  suspension  system  fastened  to  a  heavy  rope 
band,  or  girth,  encircling  the  outer  envelope.  At  the  three  points 
wiiere  the  lifting  rope  members  met,  a  shaft  running  the  length  of 
the  car  and  carrying  what  Meusnier  described  as  "revolving  oars" 
was  installed.  These  constituted  the  prototype  of  the  screw  pro- 
peller, invented  for  aerial  navigation  at  a  time  long  antedating  the 
use  of  steam  for  marine  use.  Thus  he  devised:  (1)  The  air  balloonet 
to  husband  the  gas  supply  and  thus  prevent  the  deformation  of  the 
outer  container  or  support,  as  well  as  to  provide  stability;  (2)  the 
triangular  suspension  to  attain  longitudinal  stability;  and  (3)  the 
screw  propeller  for  propulsion,  beside  selecting  the  proper  location 
for  the  latter. 

PROBLEMS  OF  THE  DIRIGIBLE 

Ability  to  Float.  If  ability  to  rise  in  the  air  depended  merely 
upon  a  knowledge  of  the  principle  that  made  it  possible,  it  undoubt- 
edly would  have  been  accomplished  many  centuries  ago.  As  already 


DIRIGIBLE   BALLOONS  9 

mentioned,  Archimedes  established  the  fact  that  a  body  upon  float- 
ing in  a  fluid  displaces  an  amount  of  the  latter  equal  in  weight  to 
the  body  itself,  and  upon  this  theory  was  formulated  the  now  well- 
known  law,  that  every  body  plunged  into  a  fluid  is  subjected  by  this 
fluid  to  a  pressure  from  below,  equivalent  to  the  weight  of  the  fluid 
displaced  by  the  body.  Consequently,  if  the  weight  of  the  latter 
be  less  than  that  of  the  fluid  it  displaces,  the  body  will  float.  It  is 
by  reason  of  this  that  the  iron  ship  floats  and  the  fish  swims  in  water. 
If  the  weight  of  the  body  and  the  displaced  water  be  the  same,  the 
body  will  remain  in  equilibrium  in  the  water  at  a  certain  level,  and 
if  that  of  the  body  be  greater,  it  will  sink.  All  three  of  these  factors 
are  found  in  the  fish,  which,  with  the  aid  of  its  natatory  gland,  can 
rise  to  the  surface,  sink  to  the  bottom,  or  remain  suspended  at  differ- 
ent level.-.  To  accomplish  these  changes  of  specific  gravity,  the  fish 
fills  this  gland  with  air,  dilating  it  until  full,  or  compressing  and 
emptying  it.  In  this  we  find  a  perfect  analogy  to  the  air  balloonet 
of  the  dirigible,  which  serves  the  same  purposes.  The  method  by 
which  lifting  power  is  obtained  in  the  dirigible  is  exactly  the  same 
as  in  the  case  of  the  balloon. 

But  once  in  the  air,  a  balloon  is,  to  all  intents  and  purposes, 
a  part  of  the  atmosphere.  There  is  absolutely  no  sensation  of  move- 
ment, either  vertically  or  horizontally.  The  earth  appears  to  drop 
away  from  beneath  and  to  sweep  by  horizontally,  and  regardless  of 
how  violently  the  wind  may  be  blowing,  the  balloon  is  always  in  a 
dead  calm  because^t  is  really  part  of  the  wind  itself  and  is  traveling 
with  it  at  exactly  the  same  speed.  If  it  were  not  for  the  loss  of  lift- 
ing power  through  the  expansion  and  contraction  of  the  gas,  making 
it  necessary  to  permit  its  escape  in  order  to  avoid  rising  to  incon- 
venient heights  on  a  very  warm  day,  and  the  sacrifice  of  ballast  to 
prevent  coming  to  earth  at  night,  the  ability  of  a  balloon  to  stay  up 
would  be  limited  only  by  the  endurance  of  its  crew  and  the  quantity 
of  provisions  it  was  able  to  transport.  As  the  use  of  air  balloonets 
in  the  dirigible  takes  care  of  this,  the  question  of  lifting  power  presents 
no  particular  difficulty.  It  is  only  a  matter  of  providing  sufficient 
gas  to  support  the  increased  weight  of  the  car,  motor  and  its  acces- 
sories, and  the  crew  of  the  larger  vessel,  with  a  factor  of  safety  to 
allow  for  emergencies,  in  order  to  permit  of  staying  in  the  air  long 
enough  to  make  a  protracted  voyage. 


10  DIRIGIBLE   BALLOONS 

Air  Resistance  vs.  Speed.  Unless  a  voyage  is  to  be  governed 
in  its  direction  entirely  by  the  wind,  the  dirigible  must  possess  a 
means  of  moving  contrary  to  the  latter.  The  moment  this  is 
attempted,  resistance  is  encountered,  and  it  is  this  resistance  of  the 
air  that  is  responsible  for  the  chief  difficulties  in  the  design  of  the 
dirigible.  To  drive  it  against  the  wind,  it  must  have  power;  to  sup- 
port the  weight  of  the  motor  necessary,  the  size  of  the  gas  bag  must 
be  increased.  But  with  the  increase  in  size,  the  amount  of  resistance 
is  greatly  multiplied  and  the  power  to  force  it  through  the  air  must 
be  increased  correspondingly.  The  law  is  approximately  as  follows : 

Where  the  surface  moves  in  a  line  perpendicular  to  its  plane,  the 
resistance  is  proportional  to  the  extent  of  the  surface,  to  the  square  of 
the  speed  with  which  the  surface  is  moved  through  the  air,  and  to  a 
coefficient,  the  mean  value  of  which  is  0.125. 

This  coefficient  is  a  doubtful  factor,  the  figure  given  having  been 
worked  out  years  ago  in  connection  with  the  propulsion  of  sailing 
vessels.  Its  value  varies  according  to  later  experimenters  between 
.08  and  .16,  the  mean  of  the  more  recent  investigations  of  Renard, 
Eiffel,  and  others  who  have  devoted  considerable  study  to  the  matter, 
being  .08.  This  is  dwelt  upon  more  in  detail  under  "Aerodynamics" 
and  it  will  be  noted  that  the  values  of  the  coefficient  K,  given  here, 
do  not  agree  with  those  stated  in  that  article.  They  serve,  how- 
ever, to  illustrate  the  principles  in  question. 

In  accordance  with  this  law,  doubling  the  speed  means  quad- 
rupling the  resistance  of  the  air.  For  instance,  a  surface  of  16  square 
feet  moving  directly  against  the  air  at  a  speed  of  10  feet  per  second 
will  encounter  a  resistance  of  16X100  (square  of  the  speed)  X  0.125 
=  200  pounds  pressure.  Doubling  the  speed,  thus  bringing  it  up 
to  20  feet  per  second,  would  give  the  equation  16  X  400  X  0.125  =  800 
pounds  pressure,  or  with  the  more  recent  value  of  the  coefficient 
of  .08,  512  pounds  pressure.  The  first  consideration  is  accord- 
ingly to  reduce  the  amount  of  surface  moving  at  right  angles.  The 
resistance  of  a  surface  having  tapering  sides  which  cut  through  or 
divide  the  molecules  of  air  instead  of  allowing  them  to  impinge 
directly  upon  it,  is  greatly  diminished;  hence,  Meusnier's  principle 
of  elongation.  If  we  take  the  same  panel  presenting  16  square  feet 
of  surface  and  build  out  on  it  a  hemisphere,  its  resistance  at  a  speed 
of  10  feet  per  second  will  be  exactly  half,  or  a  pressure  of  100  pounds. 


10 


DIRIGIBLE   BALLOONS 


11 


Giffard  Dirigible 


By  further  modifying  this  so  as  to  represent  a  sharp  point,  or  acute- 
angled  cone,  it  will  be  38  pounds.  There  could  accordingly  be  no 
question  of  attempting 
to  propel  a  spherical 
balloon. 

It  is  necessary  to 
select  a  form  that  pre- 
sents as  small  a  surface 
as  possible  to  the  air  as 
the  balloon  advances, 
while  preserving  the  max- 
imum lifting  power.  But 
experience  has  strikingly 
demonstrated  the  analogy  between  marine  and  aerial  practice — not 
only  is  the  shape  of  the  bow  of  the  vessel  of  great  importance  but, 
likewise,  the  stem.  The  profile  of  the  latter  may  permit  of  an  easy 
reunion  of  the  molecules  of  air  separated  by  the  former,  or  it  may 
allow  them  to  come  together  again  suddenly,  clashing  with  one  an- 
other and  producing  disturbing  eddies  just  behind  the  moving  body. 
To  carry  the  comparison  with  a  marine  vessel  a  bit  further,  the  form 
must  be  such  as  to  give  an  easy  "shear,"  or  sweep  from  stem  to 
stern. 

That  early  investi- 
gators appreciated  this  is 
shown  by  the  faci  that 
Giffard  in  1852,  Fig.  6, 
De  Lome  in  1872,  Fig.  7, 
Tissandier  in  1884,  and 
Santos-Dumont  in  his 
numerous  attempts,  a- 
dopted  a  spindle-shaped 
or  "fusiform"  balloon.  In 
other  words,  their  shape, 
equally  pointed  at  either 
end,  was  symmetrical  in 
relation  to  their  central  plan.  However,  that  the  shape  best 
adapted  to  the  requirements  of  the  bow  did  not  serve  equally  well 
for  the  stern,  was  demonstrated  for  the  first  time  by  Renard,  to 


Fig.  7.     De  Lome  Dirigible 


11 


12  DIRIGIBLE   BALLOONS 

whom  credit  must  be  given  for  a  very  large  part  of  the  scientific 
development  of  the  dirigible.  Almost  a  century  earlier,  Marey- 
Monge  had  laid  down  the  principle  that  to  be  successfully  pro- 
pelled through  the  air,  the  balloon  must  have  "the  head  of  a  cod 
and  the  tail  of  a  mackerel."  Nature  exemplifies  the  truth  of  this 
in  all  swiftly  moving  fishes  and  birds.  Renard  accordingly  adopted 
what  may  best  be  termed  the  "pisciform"  type,  viz,  that  of  a  dis- 
symmetrical fish  with  the  larger  end  serving  as  the  bow;  and  the 
performances  of  the  Renard,  Lebaudy,  and  Clement-Bayard  airships 
have  shown  that  this  is  the  most  advantageous  form. 

The  pointed  stern  prevents  the  formation  of  eddies  and  the 
creation  of  a  partial  vacuum  in  the  wake  which  would  impose  addi- 
tional thrust  on  the  bow.  Zeppelin  has  disregarded  this  factor  by 
adhering  to  the  purely  cylindrical  form  with  short  hemispherical 
bow  and  stern,  but  it  is  to  be  noted  that  while  other  German  inves- 
tigators originally  followed  this  precedent,  they  have  gradually 
abandoned  it,  owing  to  the  noticeable  retarding  effect. 

Critical  Size  of  Bag.  Next  in  importance  to  the  best  form  to 
be  given  the  vessel,  is  the  most  effective  size — something  which  has 
a  direct  bearing  upon  its  lifting  power.  This  depends  upon  the 
volume,  while  the  resistance  is  proportional  to  the  amount  of  sur- 
face presented.  Greater  lifting  power  can  accordingly  be  obtained 
by  keeping  the  diameter  down  and  increasing  the  length.  But  the 
resistance  is  also  proportionate  to  the  square  of  the  speed,  while 
the  volume,  or  lifting  power,  varies  as  the  cube  of  the  dimensions 
of  the  container,  so  that  in  doubling  the  latter,  the  resistance  of  the 
vessel  at  a  certain  speed  is  increased  only  four  times  while  its  lifting 
capacity  is  increased  eight  times.  Consequently  the  larger  dirigible 
is  very  much  more  efficient  than  the  smaller  one  since  it  can  carry 
so  much  more  weight  in  the  form  of  a  motor  and  fuel  in  proportion 
to  its  resistance  to  the  air.  As  an  illustration  of  this,  assume  a  rec- 
tangular container  with  square  ends  1  foot  each  way  and  5  feet  long. 
Its  volume  will  be  5  cubic  feet  and  if  the  lifting  power  of  the  gas  be 
assumed  as  2  pounds  per  cubic  foot,  its  total  lifting  power  will  be  5 
pounds.  If  a  motor  weighing  exactly  5  pounds  per  horse-power 
be  assumed,  it  will  be  evident  that  the  motor  which  such  a  balloon 
could  carry  would  be  limited  to  1  horse-power,  neglecting  the  weight 
of  the  container. 


DIRIGIBLE   BALLOONS  13 

Double  these  dimensions  and  the  container  will  then  measure 
2X2X 10  feet,  giving  a  volume  of  40  cubic  feet,  and  a  lifting  power,  on 
the  basis  already  assumed,  of  a  motor  capable  of  producing  8  horse- 
power, and  this  without  taking  into  consideration  that  as  the  size 
of  the  motor  increases,  its  weight  per  horse-power  decreases.  The 
balloon  of  twice  the  size  will  thus  have  a  motor  of  8  horse-power  to 
overcome  the  resistance  of  the  head-on  surface  of  4  square  feet,  or 
2  horse-power  per  square  foot  of  transverse  section,  whereas  the 
balloon  of  half  the  size  will  have  only  1  horse-power  per  square  foot 
of  transverse  section.  It  is,  accordingly,  not  practicable  to  construct 
small  dirigibles  such  as  the  various  airships  built  by  Santos-Dumont 
for  his  experiments,  while,  on  the  other  hand,  there  are  numerous 
limitations  that  will  be  obvious,  restricting  an  increase  in  size  beyond 
a  certain  point,  as  has  been  shown  by  the  experience  of  the  various 
Zeppelin  airships. 

To  make  it  serviceable,  what  Berget  terms  the  "independent 
speed"  of  a  dirigible,  i.e.,  its  power  to  move  itself  against  the  wind, 
must  be  sufficient  to  enable  it  to  travel  under  normally  prevailing 
atmospheric  conditions.  These  naturally  differ  greatly  in  different 
countries  and  in  different  parts  of  the  same  country.  Where  mete- 
orological tables  showed  the  prevailing  winds  in  a  certain  district 
to  exceed  15  miles  an  hour  throughout  a  large  part  of  the  year,  it 
would  be  useless  to  construct  an  airship  with  a  speed  of  15  miles 
an  hour  or  less  for  use  in  that  particular  district,  as  the  number 
of  days  in  the  year  (in  which  one  could  travel  to  and  from  a  certain 
starting  point  would  be  limited.  This  introduces  another  factor 
which  has  a  vital  bearing  upon  the  size  of  the  vessel.  Refer  to  the 
figures  just  cited  and  assume  further  that  by  doubling  the  dimensions 
and  making  the  airship  capable  of  transporting  a  motor  of  8  horse- 
power, it  has  a  speed  of  10  miles  an  hour.  It  is  desired  to  double  this. 
But  the  resistance  of  the  surface  presented  increases  as  the  square  of 
the  speed.  Hence,  it  will  not  avail  merely  to  double  the  power  of 
the  motor.  Experience  has  demonstrated  that  the  power  necessary 
to  increase  the  speed  of  the  same  body,  increases  in  proportion  to 
the  cube  of  the  speed,  so  that  instead  of  a  16-horse-power  motor  in  the 
case  mentioned,  one  of  64  horse-power  would  be  needed.  There  are, 
accordingly,  a  number  of  elements  that  must  be  taken  into  considera- 
tion when  determining  the  size  as  well  as  the  shape  of  the  balloon. 


13 


14  DIRIGIBLE   BALLOONS 

Fabric  and  Color.  As  the  gas  is  frequently  under  considerable 
pressure  when  the  balloon  expands  under  the  influence  of  the  suns' 
heat,  a  great  deal  of  experiment  has  been  necessary  to  find  the  best 
class  of  fabric  for  the  making  of  the  envelope.  Under  the  pressure, 
an  ordinary  fabric  would  stretch  and  permit  the  escape  of  a  large 
percentage  of  the  gas.  It  has  been  found  impossible  to  weave  any 
fabric  that  will  be  close  enough  to  hold  hydrogen  under  pressure, 
so  that  recourse  is  had  to  a  combination  of  cloth  and  rubber.  The 
cloth  is  an  extremely  fine  weave  of  cotton  even  lighter  and  closer 
than  the  best  of  racing  yacht  duck,  and  it  is  combined  with  rubber 
under  heavy  pressures.  Three  layers  of  this  rubberized  fabric  are 
cemented  together  to  form  what  is  known  as  "balloon  cloth,"  which 
is  about  as  impermeable  a  material  as  can  be  made  without  involv- 
ing undue  weight.  The  necessity  of  using  rubber  in  it  has  intro- 
duced a  complication,  it  having  been  found  by  experiment  that 
rubber  is  strongly  attacked  by  the  ultra-violet  rays  of  sunlight, 
which  probably  accounts  for  the  fact  that  balloon  envelopes  are 
usually  found  more  or  less  damaged  after  a  high  ascension,  the 
influence  of  these  rays  being  much  greater  at  the  higher  altitudes. 
To  offset  this,  experiments  are  being  made  in  the  introduction  of 
coloring  matter  in  the  fabric,  some  envelopes  having  been  dyed 
yellow  and  others  red.  M.  Reynaud,  who  has  conducted  a  series 
of  experiments  illustrating  the  damage  suffered  by  rubber  when 
subjected  to  the  light  of  a  mercury  vapor  lamp  with  a  quartz  tube, 
which  is  a  powerful  source  of  such  rays,  recommends  red  as  absorb- 
ing both  the  violet  and  blue  rays. 

Static  Equilibrium.  Having  settled  upon  the  size  and  shape, 
there  must  be  an  appropriate  means  of  attaching  the  car  to  carry 
the  power  plant,  its  accessories  and  control,  and  the  crew.  While 
apparently  a  simple  matter,  this  involves  one  of  the  most  important 
elements  of  the  design — that  of  stability.  A  long  envelope  of  com- 
paratively small  diameter  being  necessary  for  the  reasons  given, 
it  is  essential  that  this  be  maintained  with  its  axis  horizontal.  In 
calm  air,  the  balloon,  or  container,  is  subjected  to  the  action  of 
two  forces:  One  is  its  weight,  applied  to  the  center  of  gravity  of 
the  system  formed  by  the  balloon,  its  car,  and  all  the  supports; 
the  other  is  the  thrust  of  the  air,  applied  at  a  point  known  as  the 
center  of  thrust  and  which  will  differ  with  different  designs,  accord- 


14 


DIRIGIBLE   BALLOONS  15 

ing  as  the  car  is  suspended  nearer  or  farther  away  from  the  balloon. 
If  the  latter  contained  only  the  gas  used  to  inflate  it,  with  no  car 
or  other  weight  to  carry,  the  center  of  gravity  and  the  center  of 
thrust  would  coincide,  granting  that  the  weight  of  the  envelope  were 
negligible.  As  this  naturally  can  not  be  the  case,  these  forces  are 
not  a  continuation  of  each  other.  But  as  they  must  necessarily  be 
equal  if  the  balloon  is  neither  ascending  nor  descending,  it  follows 
that  they  will  cause  the  balloon  to  turn  until  they  are  a  continua- 
tion of  each  other,  and  in  the  case  of  a  pisciform  balloon,  this  will 
cause  it  to  tilt  downward.  Like  a  ship  with  too  much  cargo  for- 
ward, it  would  be  what  sailors  term  "down  at  the  head." 

As  this  would  be  neither  convenient  nor  compatible  with  rapid 
propulsion,  it  must  be  avoided  by  distributing  the  weight  along  the 
car  in  such  a  manner  that  when  the  balloon  is  horizontal,  the  forces 
represented  by  the  pressure  above  and  the  weight  below,  must  be  in 
the  same  perpendicular.  This  is  necessary  to  insure  static  equilibrium, 
or  a  horizontal  position  while  in  a  state  of  rest.  To  bring  this  about, 
the  connections  between  the  car  and  the  balloon  must  always  main- 
tain the  same  relative  position,  which  is  further  complicated  by  the 
fact  that  they  must  be  flexible  at  the  same  time. 

Longitudinal  Stability.  But  the  longitudinal  stability  of  the 
airship  as  a  whole  must  be  preserved,  and  this  also  involves  its 
stability  of  direction.  Its  axis  must  be  a  tangent  to  the  course  it 
describes,  if  the  latter  be  curvilinear,  or  parallel  with  the  direction 
of  this  course  where  the  course  itself  is  straight.  This  is  apparently 
something  which  should  be  taken  care  of  by  the  rudder,  any  ten- 
dency on  the  part  of  the  airship  to  diverge  from  its  course  being  cor- 
rected by  the  pilot.  But  a  boat  that  needed  constant  attention  to 
the  helm  to  keep  it  on  its  course  would  be  put  down  as  a  "cranky" 
—in  other  words,  of  faulty  design  in  the  hull.  A  dirigible  having 
the  same  defect  would  be  difficult  to  navigate,  as  the  rudder  alone 
would  not  suffice  to  correct  this  tendency  in  emergencies.  Stability 
of  direction  is,  accordingly,  provided  for  in  the  design  of  the  balloon 
itself,  and  this  is  the  chief  reason  for  adopting  the  form  of  a  large- 
headed  and  slender-bodied  fish,  as  already  outlined.  This  brings 
the  center  of  gravity  forward  and  makes  of  the  long  tail  an  effective 
lever  which  overcomes  any  tendency  of  the  ship  to  diverge  from  the 
course  it  should  follow,  by  causing  the  resistance  of  the  air  itself  to 


15 


16  DIRIGIBLE   BALLOONS 

bring  it  back  into  line.  However,  the  envelope  of  the  balloon  itself 
would  not  suffice  for  this,  so  just  astern  of  the  latter,  "stabilizing 
surfaces"are  placed,consisting  of  vertical  planes  fixed  to  the  envelope. 
These  form  the  keel  of  the  dirigible  and  are  analogous  to  the  keel  of 
the  ship.  Stability  of  direction  is  thus  obtained  naturally  without 
having  constant  recourse  to.  the  rudder,  which  is  employed  only 
to  alter  the  direction  of  travel. 

The  comparison  between  marine  and  aerial  navigation  must  be 
carried  even  further.  These  vertical  planes,  or  "keel,"  prevent 
rolling;  it  is  equally  necessary  to  avoid  pitching — far  more  so  than 
in  the  case  of  a  vessel  in  water.  So  that  while  the  question  of  sta- 
bility of  direction  is  intimately  connected  with  longitudinal  stability, 
other  means  are  required  to  insure  the  latter.  The  airship  must 
travel  on  an  "even  keel,"  except  when  ascending  or  descending, 
and  the  latter  must  be  closely  under  the  control  of  the  pilot,  as 
otherwise  the  balloon  may  incline  at  a  dangerous  angle.  This  shows 
the  importance  of  an  unvarying  connection  between  the  car  and  the 
envelope  to  avoid  defective  longitudinal  stability.  Assume,  for 
instance,  that  the  car  is  merely  attached  at  each  end  of  a  single 
line.  The  car,  the  horizontal  axis  of  the  balloon,  and  the  two  sup- 
ports would  then  form  a  rectangle.  When  in  a  state  of  equilibrium 
the  weight  and  the  thrust  are  acting  in  the  same  line.  Now  suppose 
that  the  pilot  desires  to  descend  and  inclines  the  ship  downward. 
The  center  of  gravity  is  then  shifted  farther  forward  and  the  two 
forces  are  no  longer  in  line. 

But  as  the  connections  permit  the  car  to  swing  in  a  vertical 
plane,  they  permit  the  latter  to  move  forward  and  parallel  with  the 
balloon,  thus  forming  a  parallelogram  instead  of  a  rectangle.  This 
causes  the  center  of  gravity  to  shift  even  farther,  and  as  one  of  the 
most  serious  causes  of  longitudinal  stability  is  the  movement  of  the 
gas  itself,  it  would  also  rush  to  the  back  end  and  cause  the  balloon 
to  "stand  on  its  head."  As  the  tendency  of  the  gas  is  thus  to  aug- 
ment any  inclination  accidentally  produced,  the  vital  necessity  of 
providing  a  suspension  that  is  incapable  of  displacement  with  rela- 
tion to  the  balloon  is  evident.  Here  is  where  the  importance  of  Meus- 
nier's  conception  of  the  principle  of  triangular  suspension  comes  in. 
Instead  of  being  merely  supported  by  direct  vertical  connections 
with  the  balloon,  the  ends  of  the  car  are  also  attached  to  the 


16 


DIRIGIBLE  BALLOONS  17 

opposite  ends  of  the  envelope,  forming  opposite  triangles.  This  gives 
an  unvarying  attachment,  so  that  when  the  balloon  inclines,  the  car 
maintains  its  relative  position,  and  the  weight  no  longer  being  a  pro- 
longation of  the  thrust,  the  two  forces  tend  to  pull  each  other  back 
in  the  same  line,  or,  in  other  words,  to  "trim  ship."  Granting  a 
proper  form  of  balloon  or  gas  container  to  start  with,  it  will  be  evi- 
dent that  due  attention  to  the  principles  just  outlined  will  produce 
a  vessel  that  will  not  only  hold  to  its  course  without  fatiguing  the 
pilot,  but  that  will  also  not  be  subject  to  a  tendency  to  pitch  or  roll. 
As  air  is  much  easier  to  displace  than  water,  it  will  be  evident  that 
either  of  these  characteristics  would  be  far  more  dangerous  in  an 
airship  than  in  a  marine  vessel  and  they  would  naturally  be  suf- 
ficient to  condemn  it,  even  in  the  absence  of  other  shortcomings. 

Dynamic  Equilibrium.  In  addition  to  being  able  to  preserve 
its  static  equilibrium  and  to  possess  proper  longitudinal  stability, 
the  successful  airship  must  also  maintain  its  dynamic  equilibrium— 
the  equilibrium  of  the  airship  in  motion.  This  may  be  made  clear 
by  referring  to  the  well-known  expedients  adopted  to  navigate 
the  ordinary  spherical  balloon.  To  rise,  its  weight  is  diminished  by 
gradually  pouring  sand  from  the  bags  which  are  always  carried  as 
ballast.  To  descend,  it  is  necessary  to  increase  the  total  weight  of 
the  balloon  and  its  car,  and  the  only  method  of  accomplishing  this 
is  to  permit  the  escape  of  some  of  the  gas,  the  specific  lightness 
of  which  constitutes  the  lifting  power  of  the  balloon.  As  the  gas 
escapes,  the  thrust  of  the  air  on  the  balloon  is  decreased  and  it 
sinks — the  ascensional  effort  diminishing  in  proportion  to  the 
amount  of  gas  that  is  lost.  The  balloon,  or  the  container  itself, 
being  merely  a  spherical  bag,  on  the  upper  hemispherical  half  of 
which  the  net  supporting  the  car  presses  at  all  points,  the  question 
of  deformation  is  not  a  serious  one.  Before  it  assumed  propor- 
tions where  the  bag  might  be  in  danger  of  collapsing,  the  balloon 
would  have  had  to  come  to  earth  through  lack  of  lifting  power 
to  longer  sustain  it.  Owing  to  its  far  greater  size,  as  well  as  to  the 
form  of  the  surface  which  it  presents  to  the  air  pressure,  such  a  crude 
method  is  naturally  not  applicable  to  the  dirigible. 

Dynamic  equilibrium  must  take  into  account  not  only  its  weight 
and  the  sustaining  pressure  of  the  air,  but  also  the  resistance  of  the 
air  exerted  upon  its  envelope.  This  resistance  depends  upon  the 


17 


18  DIRIGIBLE   BALLOONS 

dimensions  and  the  shape  of  that  envelope,  and  in  calculations  the 
latter  is  always  assumed  to  be  invariable.  Assume,  for  instance, 
that  to  descend  the  pilot  of  a  dirigible  allowed  some  of  the  hydrogen 
gas  to  escape.  As  the  airship  came  down,  it  would  have  to  pass 
through  strata  of  air  of  constantly  increasing  pressure  as  the  earth 
is  approached.  The  reason  for  this  will  be  apparent  as  the  lower 
strata  bear  the  weight  of  the  entire  atmosphere  above  them.  The 
confined  gas  will  no  longer  be  sufficient  to  distend  the  envelope, 
the  latter  losing  its  shape  and  becoming  flabby.  As  the  original 
form  is  no  longer  retained,  the  center  of  resistance  of  the  air  will 
likewise  have  changed  together  with  the  center  of  thrust,  and  the 
initial  conditions  will  no  longer  obtain.  But  as  the  equilibrium  of 
the  airship  depends  upon  the  maintenance  of  these  conditions,  it 
will  be  lost  if  they  vary.  * 

Function  of  Balloonets.  In  the  function  of  balloonets  is  realized 
the  importance  of  the  principle  established  by  Meusnier.  It  was 
almost  a  century  later  before  it  was  rediscovered  by  Dupuy  de  Lome 
in  connection  with  his  attempts  to  make  balloons  dirigible.  That 
the  balloon  must  always  be  maintained  in  a  state  of  perfect  infla- 
tion has  been  pointed  out.  But  gas  is  lost  in  descents  and  to  a 
certain  extent,  through  the  permeability  of  the  envelope.  Unless 
it  is  replaced,  the  balloon  will  be  only  partially  inflated.  In  view 
of  the  great  volume  necessary,  it  requires  no  explanation  to  show 
that  it  would  be  impossible  to  replace  the  gas  itself  by  fresh  hydrogen 
carried  on  the  car.  It  would  have  to  be  under  high  pressure  and 
the  weight  of  the  steel  cylinders  as  well  as  the  number  necessary  to 
transport  a  sufficient  supply  would  be  prohibitive.  Hence,  Meus- 
nier conceived  the  idea  of  employing  air.  But  this  could  not  be 
pumped  directly  into  the  balloon  to  mix  with  the  hydrogen  gas, 
as  the  resulting  mixture  would  not  only  still  be  as  inflammable  as 
the  former  alone,  but  it  would  also  contain  sufficient  oxygen  to 
create  a  very  powerful  and  infinitely  more  dangerous  explosive. 
This  led  to  the  adoption  of  the  air  balloonet. 

In  principle  the  balloonet  consists  of  dividing  the  interior  of  the 
envelope  into  two  cells,  the  larger  of  which  receives  the  light  gas 
while  the  smaller  is  intended  to  hold  air  and  terminates  in  a  tube 
extending  down  to  a  pump  in  the  car.  In  other  words,  a  fabric 
partition  adjacent  to  the  lower  part  of  the  envelope  inside  and  sub- 


18 


DIRIGIBLE   BALLOONS  19 

ject  to  deformation  at  will.  In  actual  practice  it  consists  of  a  num- 
ber of  independent  cells  of  this  kind,  longitudinally  disposed  along 
the  lower  half  of  the  interior  of  the  envelope,  as  in  the  case  of  Well- 
man's  "  America,  "which  was  equipped  with  a  number  of  air  bal- 
loonets, the  location  of  which  may  be  noted  by  referring  to  the 
illustrations  of  this  airship,  Fig.  19. 

When  the  balloon  is  completely  inflated  with  hydrogen,  as  at 
the  beginning  of  an  ascent,  these  balloonets  lie  flat  against  the  lower 
part  of  the  envelope,  exactly  like  a  lining.  As  the  airship  rises,  the 
gas  expands  owing  to  the  reduction  in  atmospheric  pressure  at  a 
higher  altitude,  as  well  as  to  the  influence  of  heat.  With  the  increase 
in  pressure,  uniform  inflation  is  maintained  by  the  escape  of  a  cer- 
tain amount  of  gas  through  the  automatic  valves  provided  for  the 
purpose.  Unless  this  took  place,  the  internal  pressure  might  assume 
proportions  placing  the  balloon  in  danger  of  blowing  up.  To  avoid 
this,  a  pressure  gauge  communicating  with  the  gas  compartment 
is  one  of  the  most  important  instruments  on  the  control  board  of 
the  car,  and  should  its  reading  indicate  a  failure  of  the  automatic 
valves,  the  pilot  must  reduce  the  pressure  by  operating  a  hand 
valve..  But  as  the  car  descends,  the  increased  external  pressure 
causes  a  recontraction  of  the  gas  until  it  no  longer  suffices  to  fill  the 
envelope.  To  replace  the  loss  the  air  pumps  are  utilized  to  force 
air  into  the  air  balloonets  until  the  sum  of  the  volumes  of  gas  and 
air  in  the  different  compartments  equals  the  original  volume.  In 
this  manner,  the  ^nitial  conditions,  upon  which  the  equilibrium  of 
the  airship  is  based,  are  always  maintained. 

This  is  not  the  only  method  of  correcting  for  change  in  volume, 
nor  of  maintaining  the  longitudinal  stability  of  the  whole  fabric, 
the  importance  of  which  has  already  been  detailed,  but  experience 
has  shown  that  it  is  the  most  practical.  It  is  possible  to  give  the 
balloon  a  rigid  frame  over  which  the  envelope  is  stretched  and  to 
attach  the  car  by  means  of  a  rigid  metal  suspension,  as  in  the  various 
Zeppelin  airships,  or  to  take  it  semi-rigid,  as  in  the  Gross,  another 
German  type  in  which  Zeppelin's  precedent  was  followed  only  in 
the  case  of  the  suspension.  To  prevent  deformation  by  this  means, 
the  balloon  is  provided  with  an  absolutely  rigid  skeleton  of  aluminum 
tubes.  This  framing  is  in  the  shape  of  a  number  of  uniform  cylin- 
drical sections,  or  gas  compartments,  each  one  of  which  accom- 


19 


20  DIRIGIBLE   BALLOONS 

modates  an  independent  balloon,  while  over  the  entire  frame  a  very 
strong  but  light  fabric  constituting  the  outer  or  protecting  envelope 
is  stretched  taut.  The  idea  of  the  numerous  independent  balloons 
is  to  insure  a  high  factor  of  safety  as  the  loss  of  the  entire  contents 
of  two  or  three  of  them  through  accident  would  not  dangerously 
affect  the  lifting  power  of  the  whole.  Apart  from  its  great  expense, 
the  rigid  nature  of  this  construction  makes  it  a  delicate  thing  to 
handle  on  the  ground,  as  witness  the  numerous  wrecks  that  have 
attended  the  landings  of  the  huge,  non-flexible  mass.  To  minimize 
this  risk  in  starting,  its  "home  port"  had  to  be  made  in  the  form  of 
a  floating  shed,  anchored  only  at  one  end  so  that  the  ship  could  always 
emerge  to  "leeward." 

The  system  of  air  balloonets  has  accordingly  been  adopted  by 
every  other  designer,  in  variously  modified  forms,  as  illustrated  by 
the  German  dirigible  Parseval,  in  which  but  two  air  bags  were 
employed,  one  at  either  end.  They  were  interconnected  by  an  external 
tube  to  which  the  air-pump  discharge  was  attached,  and  were  also 
operated  by  a  counterbalancing  system  inside  the  gas  bag,  by  means 
of  which  the  inflation  of  one  balloonet,  as  the  after  one,  for  example, 
caused  the  collapse  of  the  other. 

Influence  of  Fish  Form  of  Bag.  But  a  condition  of  dynamic 
equilibrium  can  not  be  obtained  with  the  combined  aid  of  the  pre- 
cautions already  noted  to  secure  longitudinal  stability  and  that  of 
the  air  balloonet  in  maintaining  uniform  inflation.  Why  this  is  so 
will  be  clear  from  a  simple  example.  If  a  simple  fusiform  or  spindle- 
shaped  balloon  be  suspended  in  the  air  in  a  horizontal  plane,  the 
axis  of  which  passes  through  its  center  of  gravity,  it  would  be  prac- 
tically pivoted  on  the  latter  and  would  be  extremely  sensitive  to 
influences  tending  to  tilt  it  up  or  down.  It  would  be  in  a  state  of 
"indifferent"  longitudinal  equilibrium.  As  long  as  the  axis  of  the  bal- 
loon remains  horizontal  and  the  air  pressure  is  coincident  with  that 
axis,  it  will  be  in  equilibrium,  but  an  equilibrium  essentially  unstable. 
Experiment  proves  that  the  moment  the  balloon  inclines  from 
the  horizontal  in  the  slightest  degree,  there  is  a  strong  tendency 
for  it  to  revolve  about  its  center  of  gravity  until  it  stands  vertical 
to  the  air  current,  or  is  standing  straight  up  and  down.  This,  of 
course,  refers  to  the  balloon  alone  without  any  attachments.  Such 
a  tendency  would  be  fatal,  amounting  as  it  does  to  absolute  instability. 


DIRIGIBLE  BALLOONS  21 

If  instead  of  symmetrical  form,  tapering  toward  both  ends,  a 
pisciform  balloon  be  tried,  it  will  still  evidence  the  same  tendency, 
but  in  greatly  diminished  degree.  This  is  not  merely  the  theory 
affecting  its  stability  but  represents  the  findings  of  Col.  Charles 
Renard,  who  undoubtedly  did  more  to  formulate  the  exact  laws 
governing  the  stability  of  a  dirigible  than  any  other  investigator  in 
this  field.  His  data  is  the  result  of  a  long  and  methodically  carried 
out  series  of  experiments.  In  the  case  of  the  pisciform  balloon,  the 
disturbing  effect  is  due  in  unequal  degree,  to  the  diameter  of  the 
balloon  and  its  inclination  and  speed,  whereas  the  steadying  effect 
depends  upon  the  inclination  and  diameter,  but  not  on  the  speed. 
The  disturbing  effect,  therefore,  depends  solely  on  the  speed  and 
augments  very  rapidly  as  the  speed  increases.  It  will,  accordingly, 
be  apparent  that  there  is  a  certain  speed  for  which  the  two  effects 
are  equal,  and  beyond  which  the  disturbing  influence,  depending  on 
speed,  will  overcome  the  steadying  effect. 

To  this  rate  of  travel,  Renard  applied  the  term  "critical  speed," 
and  when  this  is  exceeded  the  equilibrium  of  the  balloon  becomes 
unstable.  To  obtain  this  data,  keels  of  varying  shapes  and  dimen- 
sions were  submitted  to  the  action  of  a  current  of  air,  the  force  of 
which  could  be  varied  at  will.  In  the  case  of  the  La  France,  the  first 
fish-shaped  dirigible,  the  critical  speed  was  found  to  be  10  meters, 
or  approximately  39  feet  per  second,  a  speed  of  21.6  miles  per  hour, 
and  a  24-horse-power  motor  suffices  to  drive  the  airship  at  this  rate 
of  travel.  But  the  internal  combustion  motor  is  now  so  light  that 
a  dirigible  of  this  type  could  easily  lift  a  motor  capable  of  generating 
80  to  100  horse-power.  With  this  amount  of  power,  its  theoretic 
speed  would  be  50  per  cent  greater,  or  33  miles  an  hour.  But  this 
could  not  be  accomplished  in  practice  as  long  before  it  was  reached 
the  stability  would  become  precarious.  As  Colonel  Renard  observed 
in  the  instance  just  cited,  "If  the  balloon  were  provided  with  a  100- 
horse-power  motor,  the  first  24  horse-power  would  make  it  go  and 
the  other  76  horse-power  would  break  our  necks." 

Steadying  Planes.  It  is  accordingly  necessary  to  adopt  a  further 
expedient  to  insure  stability.  This  takes  the  form  of  a  System  of 
rigid  planes,  both  vertical  and  horizontal,  located  in  the  axis  of  the 
balloon  and  placed  a  considerable  distance  to  the  rear  of  the  center 
of  gravity.  With  this  addition,  the  resemblance  of  the  after  end  of 


21 


22 


DIRIGIBLE   BALLOONS 


the  balloon  to  the  feathering  of  an  arrow  is  apparent,  while  its  pur- 
pose is  similar  to  that  of  the  latter.  For  this  reason,  these  steadying 
planes  have  been  termed  the  empennage,  which  is  the  French  equiva- 
lent of  " arrow  feathering,"  while  its  derivative  empennation  is 
employed  to  describe  the  counteraction  of  this  disturbing  effect. 
In  the  La  France,  which  measured  about  230  feet  in  length  by  40 
feet  in  diameter,  the  area  of  the  planes  required  to  accomplish  this 
was  160  square  feet,  and  the  planes  themselves  were  placed  almost  100 
feet  to  the  rear  of  the  center  of  gravity.  By  referring  to  the 


Fig.  8.     La  Ville  de  Paris  Showing  Balloonets 

illustrations  of  the  various  French  airships,  the  various  developments 
in  the  methods  of  accomplishing  this  will  be  apparent. 

In  the  Lebaudy  balloon,  it  took  the  form  of  planes  attached  to 
the  framework  between  the  car  and  the  balloon.  In  La  Patrie 
and  La  Republique,  the  resemblance  to  the  feathered  arrow  was 
completed  by  attaching  four  planes  in  the  form  of  a  cross  directly 
to  the  stern  of  the  balloon  itself.  But  as  weight,  no  matter  how  slight, 
is  a  disturbing  factor  at  the  end  of  a  long  lever,  such  as  is  represented 


22 


DIRIGIBLE   BALLOONS  23 

by  the  balloon,  Renard  devised  an  improvement  over  these  methods 
by  conceiving  the  use  of  hydrogen  balloonets  as  steadying  planes. 
This  idea  was  first  embodied  in  La  Ville  de  Paris,  Fig.  8,  in  the  form 
of  cylindrical  balloonets,  and  as  conical  balloonets  on  the  Clement- 
Bayard.  These  balloonets  communicate  with  the  gas  chamber  proper 
of  the  balloon  and  consequently  exert  a  lifting  pressure  which  com- 
pensates for  their  weight,  so  that  they  no  longer  have  the  draw- 
back of  constituting  an  unsymmetrical  supplementary  load.  Zep- 
pelin provides  for  dynamic  stability  by  the  use  of  an  extremely 
long  car  along  the  length  of  which  a  considerable  weight  in  con- 
centrated form  may  be  displaced  to  counteract  any  tendency  to  tilt. 
This,  however,  has  the  disadvantage  of  placing  a  great  and  com- 
paratively useless  additional  burden  on  the  lifting  power  of  the  car, 
and  is  neither  simple  nor  automatic  in  its  action,  as  is  the  empennage. 

Location  of  Propeller.  The  final  factor  of  importance  in  the 
design  of  the  successful  dirigible,  is  the  proper  location  of  the  pro- 
pulsive effort  with  relation  to  the  balloon.  Theoretically,  this  should 
be  applied  to  the  axis  of  the  balloon  itself,  as  the  latter  represents  the 
greater  part  of  the  resistance  offered  to  the  air.  At  least  one  attempt 
to  carry  this  out  in  practice  resulted  disastrously,  that  of  the  Brazilian 
airship  Pax,  while  the  form  adopted  by  Rose  in  which  the  propeller 
was  placed  between  the  twin  balloons  in  a  plane  parallel  with  their 
horizontal  axes,  was  not  a  success.  In  theory,  the  balloon  offers  such 
a  substantial  percentage  of  the  total  resistance  to  the  air  that  the 
area  of  the  car  and  the  rigging  were  originally  considered  practically 
negligible  by  comparison.  Actually,  however,  this  is  not  the  case. 
Calculation  shows  that  in  the  case  of  any  of  the  typical  French  airships 
mentioned,  the  sum  of  the  surface  of  the  suspending  rigging  alone  is 
easily  the  equivalent  of  2  square  meters,  or  about  21  square  feet, 
without  taking  into  consideration  the  numerous  knots,  splices,  pulleys, 
and  ropes  employed  in  the  working  of  the  vessel,  air  tubes  commu- 
nicating with  the  air  balloonets,  and  the  like.  Add  to  this  equivalent 
area  that  of  the  passengers,  the  air  pump,  other  transverse  members 
and  exposed  surfaces,  and  the  total  will  be  found  equivalent  to  a  quar- 
ter or  even  a  third  of  the  transverse  section  of  the  balloon  itself. 

To  insure  the  permanently  horizontal  position  of  the  ship  under 
the  combined  action  of  the  motor  and  the  air  resistance,  a  position 
of  the  propeller  at  a  point  about  one-third  of  the  diameter  of  the 


23 


24  DIRIGIBLE   BALLOONS 

balloon  below  its  horizontal  axis  will  be  necessary.  Without  employ- 
ing a  rigid  frame  like  that  of  the  Zeppelin  and  the  Pax,  however,  such 
a  location  of  the  shaft  is  a  difficult  matter  for  constructional  reasons. 
Consequently,  it  has  become  customary  to  apply  the  driving  effort 
to  the  car  itself,  as  no  other  solution  of  the  problem  is  apparent. 
This  accounts  for  the  tendency  common  in  the  dirigible  to  "float  high 
forward,"  and  this  tilting  becomes  more  pronounced  in  proportion  to 
the  distance  the  car  is  hung  beneath  the  balloon.  The  term  "devia- 
tion" is  employed  to  describe  this  tilting  effect  produced  by  the  action 
of  the  propeller.  Conflicting  requirements  are  met  with  in  attempting 
to  reduce  this  by  bringing  the  car  closer  to  the  balloon  as  this  approx- 
imation is  limited  by  the  danger  of  operating  the  gasoline  motor  too 
close  to  the  huge  volume  of  inflammable  gas.  The  importance  of 
this  factor  may  be  appreciated  from  the  fact  that  if  the  car  were 
placed  too  far  from  the  balloon,  the  propulsive  effect  would  tend  to 
hold  the  latter  at  an  angle  without  advancing  much,  owing  to  the 
vastly  increased  air  resistance  of  the  much  larger  surface  thus  pre- 
sented. The  best  solution  of  the  problem  has  been  found  by  placing 
the  motor  in  the  car  and  driving  a  shaft  located  between  the  car  and 
the  balloon  by  means  of  a  chain. 

This  has  not  been  very  generally  followed,  however,  owing  to  the 
different  ideas  prevailing  as  to  the  best  location  for  the  propeller 
itself.  In  the  Ville  de  Paris  and  the  Clement-Bayard,  it  is  placed  at 
the  bow  and  serves  to  draw  the  balloon  along.  Earlier  attempts, 
such  as  Giffard's,  De  Lome's,  and  the  Tissandier  airship,  patterned 
after  marine  practice  by  placing  it  at  the  stern.  The  constructor  of 
the  Lebaudy  and  La  Patrie  adopted  the  use  of  two  propellers,  placed 
on  either  side  of  the  car  and  almost  in  a  line  with  its  center,  this  also 
being  the  case  in  the  design  of  the  America,  except  that  the  latter 
was  provided  with  four  screws  altogether,  two  of  which  were  on 
swiveling  joints  to  allow  of  their  being  utilized  to  either  drive  the  ship 
ahead,  or  to  assist  in  its  ascent  or  descent  by  being  driven  at  right 
angles  to  their  shaft.  Zeppelin  also  employs  four  propellers  placed 
along  the  sides  of  the  car.  The  United  States  army  dirigible  has 
the  screw  forward,  while  the  British  military  airship  carries  it  at  the 
stern  of  a  very  short  car.  On  the  whole,  its  location  at  the  bow 
would  appear  to  offer  the  greatest  advantage,  where  a  single  propeller 
is  employed. 


DIRIGIBLE   BALLOONS  25 

Relations  of  Speed  and  Radius  of  Travel.  The  various  factors 
influencing  the  speed  of  a  dirigible  have  already  been  referred  to,  but 
it  will  be  apparent  that  the  radius  of  action  is  of  equally  great  impor- 
tance. It  is  likewise  something  that  has  a  very  direct  bearing  upon 
the  speed  and,  in  consequence,  upon  the  design  as  a  whole.  It  will 
be  apparent  that  to  be  of  any  great  value  for  military  or  other  pur- 
poses, the  dirigible  must  possess  not  only  sufficient  speed  to  enable 
it  to  travel  to  any  point  of  the  compass  under  ordinarily  prevailing 
conditions  of  wind  and  weather,  but  it  must  likewise  be  able  to  remain 
in  the  air  for  some  time  and  cover  considerable  distance  under  its  own 
power.  In  fact,  one  of  the  chief  advantages  possessed  by  the  dirigible 
over  the  aeroplane  at  present  is  its  ability  to  make  long-sustained 
flights,  while  carrying  a  comparatively  large  crew  and  a  great  deal 
of  extra  weight. 

Total  Weight  per  Horse-Power  Hour.  As  is  the  case  in  almost 
every  point  in  the  design  of  the  dirigible,  conflicting  conditions  must 
be  reconciled  in  order  to  provide  it  with  a  power  plant  affording 
sufficient  speed  with  ample  radius  of  action.  It  has  already  been 
pointed  out  that  power  requirements  increase  as  the  cube  of  the  speed, 
making  a  tremendous  addition  necessary  to  the  amount  of  power 
to  obtain  a  disproportionately  small  increase  in  velocity.  In  this 
connection  there  is  a  phase  of  the  motor  question  that  has  not  received 
the  attention  it  merits  up  to  the  present  time.  The  struggle  to  reduce 
weight  to  the  attainable  minimum  has  made  weight  per  horse-power 
apparently  the  pkramount  consideration — a  factor  to  which  other 
things  could  be  sacrificed.  And  this  is  quite  as  true  of  the  aeroplane 
motor  as  those  designed  for  use  in  the  dirigible.  But  it  is  quite  as 
important  to  make  the  machine  go  as  it  is  to  raise  it  in  the  air,  so  that 
the  question  of  total  weight  per  horse-power  hour  will  undoubtedly 
come  in  for  much  more  attention  in  future,  particularly  since  weight 
per  horse-power  appears  to  have  approached  so  closely  the  minimum 
attainable,  consistent  with  a  due  regard  for  reliability. 

The  relative  importance  of  these  two  factors  may  be  appreciated 
from  the  following  illustration: 

Assume,  for  instance,  a  100  horse-power  motor  of  a  total  weight 
of  1,000  pounds,  round  numbers  being  chosen  merely  for  the  sake  of 
simplicity.  The  weight  per  horse-power  of  such  an  engine  would  be 
10  pounds.  This  would  not  be  sufficient  data,  however,  from  which 


26  DIRIGIBLE   BALLOONS 

the  design  of  a  dirigible  to  employ  that  motor  could  be  worked  out. 
Pounds  per  horse-power  usually  refers  to  a  bare  engine.  The  weight 
of  cooling  water,  lubricants,  accessories,  and  last,  but  far  from  least, 
that  of  the  fuel,  must  be  added.  For  example,  the  motor  referred 
to  may  be  assumed  to  require  1  pound  of  fuel  and  lubricant  per  horse- 
power per  hour  to  run  it  at  its  normal  output — i.  e.,  100  horse-power. 
This  means  that  it  will  consume  100  pounds  per  hour,  or  for  a  run  of  10 
hours,  1,000  pounds,  and  this  weight  must  be  added  to  that  of  the 
motor  itself  in  considering  the  design  from  the  standpoint  of  radius 
of  action.  On  the  above  basis,  1,000  horse-power  hours  will,  be 
obtainable,  and  dividing  the  total  weight  of  motor  and  supplies 
(2,000  pounds)  by  this,  would  give  a  weight  of  2  pounds  per  horse- 
power hour. 

This  factor  depends  entirely  upon  the  efficiency  of  the  motor, 
while  its  weight  per  horse-power  is  a  question  of  its  construction  alone. 
It  requires  no  abstruse  calculations  to  show  that  it  is  quite  possible 
to  have  the  same  number  of  pounds  for  the  weight  per  horse-power 
of  a  very  light  engine  that  consumes  a  great  deal  of  fuel,  as  it  is  with 
a  heavy  engine  that  consumes  very  little.  The  diminution  of  the 
weight  per  horse-power  hour  makes  possible  an  increase  in  the 
duration  of  the  voyage,  which  is  a  very  desirable  advantage,  but  as 
the  prime  factor  is  ability  to  rise,  improvement  that  involves  the 
addition  of  the  weight  is  closely  restricted  by  the  lifting  power  avail- 
able, so  that  radius  of  action  is  governed  by  numerous  considerations, 
as  will  be  seen  from  the  following: 

Take  a  dirigible  with  a  gas  capacity  of  12,000  cubic  feet,  equipped 
with  two  60-horse-power  motors,  giving  it  a  speed  of  36  miles  per 
hour.  The  engines  will  consume  130  pounds  of  fuel  per  hour,  and 
the  machine,  with  6  passengers,  will  have  sufficient  lifting  capacity  to 
carry  1,300  pounds  of  gasoline.  This  would  mean  traveling  for  10 
hours,  or  5  hours  in  each  direction,  if  necessary  to  return  to  the 
starting  point  as  is  usually  the  case.  This  would  mean  traveling  180 
miles  from  the  start — in  other  words,  the  radius  of  action  of  this 
dirigible  would  be  180  miles.  But  this  is  based  on  traveling  at 
maximum  speed  for  the  entire  period,  disregarding  the  prevailing 
winds,  the  influence  of  which  will  be  taken  up  later.  War  vessels 
seldom  steam  for  any  length  of  time  at  full  speed,  except  in  emer- 
gencies. They  run  under  reduced  power,  or  at  a  "cruising  speed," 


DIRIGIBLE   BALLOONS  27 

thus  greatly  extending  their  available  radius  of  action.  The  same 
thing  may  be  done  with  the  dirigible.  By  using  only  one  of  the 
motors  of  the  airship  in  question,  the  period  for  which  it  could  travel 
would  be  doubled.  The  propelling  power  will  be  then  only  60  horse- 
power. The  speed  will  be  divided  by  the  cubic  root  of  2,  bringing  it 
down  to  approximately  29  miles  an  hour.  But  as  the  single  motor 
will  consume  only  65  pounds  of  fuel  per  hour,  it  will  have  20  hours 
of  travel,  or  10  hours  to  go  and  10  to  return,  so  that  its  radius  of  action 
will  be  290  miles.  The  importance  of  this  in  the  application  of  aerial 
navigation  to  military  service  will  be  plain. 

Speed  is  quite  as  costly  in  an  airship  as  it  is  in  an  Atlantic  liner. 
To  double  it,  the  motor  power  must  be  multiplied  by  8,  and  the 
machine  must  carry  8  times  as  much  fuel.  But  by  cutting  the  power 
in  half,  the  speed  is  reduced  only  one-fifth.  The  problem  of  long 
voyages  in  the  dirigible  is,  accordingly,  how  to  reconcile  best  the 
minimum  speed  which  will  enable  it  to  effectively  make  way  against 
the  prevailing  winds,  with  the  reduction  in  power  necessary  to  cut 
the  fuel  consumption  down  to  a  point  that  will  insure  a  long  period  of 
running.  From  the  above  discussion,  it  is  evident  that  at  least  two 
independent  motors  should  be  provided,  so  that  under  favorable 
weather  conditions,  only  one  need  be  employed,  while  the  total  power 
of  both  could  be  called  upon  in  emergencies.  This  was  the  expedient 
adopted  in  the  instance  of  the  America,  designed  to  make  a  3,000- 
mile  voyage. 

Influence  of  Wind.  But  the  wind  is  a  serious  factor  that  has  to 
be  taken  into  consideration.  Radius  of  action  as  above  illustrated 
has  been  based  entirely  upon  traveling  in  a  dead  calm.  True,  where 
the  prevailing  wind  blew  from  a  certain  quarter  for  a  length  of  time, 
its  favoring  influence  in  going  would  be  neutralized  by  its  resistance 
in  returning,  so  that  the  result  would  be  the  same,  provided  the  velocity 
of  the  wind  were  not  too  great  to  prevent  returning  at  all  against  it. 
But  with  the  perversity  of  inanimate  things,  the  wind  may  always  be 
in  the  wrong  direction,  or  seemingly  so.  Or  again,  the  strong  wind 
which  retards  progress  on  the  outgoing  trip,  may  die  down  to  a  perfect 
calm  when  it  is  time  to  return,  so  that  the  disadvantage  of  having  to 
travel  against  it  will  not  be  compensated  for  by  extra  speed  returning. 
The  wind  is  something  with  which  the  aeronaut  must  always  figure, 
quite  as  much  as  the  sailor. 


27 


28 


DIRIGIBLE   BALLOONS 


TABLE  1 
Speed*  of  the  Wind  for  the  Vicinity  of  Paris 


Speed  of  Wind  in  Feet 
per  Sscond 

Speed  of  Wind  in  Miles 
per  Hour 

Number  of  Days  per  Year 
when  Velocity   might 
be  less  than  given  in 
the  first  two  columns 

10 

6.8 

39 

20 

13.6 

117 

30 

20.5 

197 

40 

27.3 

258 

50 

34.1 

297 

60 

40.9 

323 

70 

47.7 

342 

80 

54.6 

350 

90 

61.4 

354 

100 

68.2 

358 

.      110 

75. 

361 

120 

81.8 

363 

130 

88.7 

364 

140 

95.5 

364 

150 

102.3 

364 

160 

109.1 

365 

170 

116. 

365 

180 

122.8 

365 

*The  above  speed  values  are  only  approximations  to  the  metric  quantities. 

When  the  speed  of  the  dirigible  is  greater  than  that  of  the  prevail- 
ing wind,  it  may  travel  in  any  direction ;  when  it  is  considerably  less, 
it  can  travel  only  with  the  wind ;  when  it  is  equal  to  the  speed  of  the 
latter,  it  may  travel  at  an  angle  with  the  wind — in  other  words,  tack, 
as  a  ship  does,  utilizing  the  pressure  of  the  contrary  wind  to  force  the 
ship  against  it.  But  as  the  air  does  not  offer  the  same  hold  on  it  to 
the  hull  of  the  airship,  as  water  does  to  that  of  the  seagoing  ship,  the 
amount  of  leeway  or  drift  in  such  a  maneuver  would  doubtless  be 
excessive.  This  briefly  sums  up  a  subject  to  which  many  pages  are 
devoted  in  the  textbooks,  and  it  applies  quite  as  much  to  the  aero- 
planes as  it  does  to  the  dirigible. 

As  the  wind  has  always  been  a  factor  of  great  importance,  care- 
fully compiled  meteorological  tables  accurately  indicate  the  winds 
that  are  to  be  expected  on  the  ocean  in  any  part  of  the  globe  at 
different  seasons  in  the  year,  giving  their  direction,  average  strength, 
or  velocity,  and  the  number  of  days  per  year  on  which  certain  winds 


DIRIGIBLE  BALLOONS  29 

may  reasonably  be  looked  for.  Data  of  a  similar  nature  is  largely 
lacking  with  regard  to  the  land,  but  now  that  aerial  navigation  is  so 
prominently  to  the  fore,  it  will  undoubtedly  receive  the  attention  it 
deserves.  In  fact,  this  has  already  been  done  for  the  vicinity  of 
Paris,  and  likewise  in  several  parts  of  Germany  and  Sweden,  where 
accurate  observations  have  been  made  to  determine  the  possibility 
of  employing  wind  wheels  for  power  purposes.  The  importance  of 
such  tables  to  the  aeronaut  will  be  apparent.  Table  I  is  given  by 
Berget  as  applying  to  the  vicinity  of  Paris. 

It  requires  only  a  superficial  study  of  this  table  to  demon- 
strate that  the  vicinity  of  Paris  is  a  favorable  district  for  the  naviga- 
tion of  dirigibles  of  moderate  power  and  speed.  Take  an  airship 
having  a  speed  of  only  22.3  (36  kilometers)  miles  per  hour  as  an 
instance  of  this.  The  table  shows  that  there  are  258  days  in  a  year 
when  the  velocity  of  the  wind  is  less  than  40  feet  per  second.  By 
increasing  this  to  27.9  miles  per  hour  (45  kilometers),  which  is  the 
speed  of  the  Clement-Bayard,  the  Republique,  and  Le  Ville  de 
Paris,  it  will  be  evident  that  such  a  balloon  would  be  dirigible  on 
an  average  of  297  days  out  of  the  365,  or  about  ten  months  out  of 
the  twelve.  But,  as  has  been  shown  by  the  observations  made  from 
the  Eiffel  Tower,  the  speed  of  the  wind  is  very  much  less  near  the 
ground  than  it  is  at  greater  altitudes.  In  the  locality  in  question, 
observations  indicate  that  the  average  velocity  of  the  wind  the  year 
round,  at  the  level  of  the  house  tops,  is  between  8  and  10  feet  per 
second,  while  at  the  Top  of  the  tower,  or  1,000  feet  from  the  ground, 
it  is  32  feet.  To  again  refer  to  the  table,  it  will  be  seen  that  by  giving 
an  airship  an  independent  speed  of  slightly  over  43  miles  per  hour, 
it  will  be  navigable  on  350  days  out  of  the  year,  and  as  the  days  on 
which  the  wind  velocity  exceeds  80  feet  per  second  are  those  of 
bad  storms,  in  which  neither  the  dirigible  nor  the  aeroplane  would 
be  an  ideal  means  of  transport,  the  problem  where  the  former  is 
concerned  would  appear  to  find  its  solution  in  an  increase  of  its  speed 
to  this  point.  To  do  this  and  still  provide  an  effective  radius  of  action 
with  the  present  percentage  of  efficiency  of  the  average  light  motor 
built  for  aeronautical  use  is  not  an  easy  matter,  particularly  as  the 
greatly  increased  air  resistance  would  also  involve  a  much  stronger 
envelope  to  stand  the  high  pressure.  This  means  added  weight  and 
cuts  down  the  lifting  power  for  the  same  volume,  while  increasing 


30  DIRIGIBLE  BALLOONS 

the  latter  means  greatly  augmented  air  resistance  and  greater  power 
'to  attain  the  same  speed. 

FRENCH  DIRIGIBLES 

The  First  Lebaudy.  The  interest  evidenced  by  the  German 
War  Department  in  Zeppelin's  airship  was  more  than  duplicated 
by  that  aroused  in  French  military  circles  by  the  success  of  the 
Lebaudy  Brothers.  Since  1900  these  two  brothers  had  been  experi- 
menting with  dirigible  balloons.  Their  first  dirigible — built  by  the 
engineer  Juillot — made  thirty  flights,  in  all  but  two  of  which  it  suc- 
ceeded in  returning  to 'its  starting  point.  This  machine  was  some- 
what similar  to  the  later  types  built  by  Santos-Dumont,  and  carried 
a  40-horse-power  Daimler  motor.  A  speed  of  36  feet  per  second, 
or  about  25  miles  per  hour,  was  obtained.  During  tests  in  the  sum- 
mer of  1904,  the  balloon  was  dashed  against  a  tree  and  almost  entirely 
destroyed. 

Lebaudy  1904.  The  next  year  the  "Lebaudy  1904"  appeared. 
This  was  190  feet  long  and  had  a  capacity  of  94,000  cubic  feet  of 
gas.  The  air  bag  was  divided  into  three  parts  and  contained  17,600 
cubic  feet  of  air.  It  was  supplied  with  air  from  a  fan  driven  by  the 
engine,  and  an  auxiliary  electric  motor  and  storage  battery  were 
carried  to  drive  the  fan  when  the  gas  engine  was  not  working.  The 
storage  battery  was  also  used  to  furnish  electric  lights  for  the  airship. 
A  horizontal  sail  of  silk  w^as  stretched  between  the  car  and  the  gas 
bag.  This  had  an  area  of  something  over  1,000  square  feet,  and  a 
sort  of  keel  of  silk  was  stretched  below  it.  A  horizontal  rudder, 
shaped  like  a  pigeon's  tail,  was  used  at  the  rear,  and  immediately 
behind  it  were  two  V-shaped  vertical  rudders.  A  small  vertical 
sail  was  carried,  which  could  be  used  to  assist  in  guiding  the  airship. 
The  car  was  16  feet  long,  and  was  rigidly  hung  10  feet  below  the  bag. 
It  was  provided  with  an  inverted  pyramid  of  steel  tubes  meeting 
at  an  apex  below  the  car  to  prevent  injury  in  alighting.  Sixty- 
three  ascents  were  made  in  1904  with  this  balloon,  all  of  them  com- 
paratively successful,  the  longest  being  a  journey  of  60  miles  in  two 
hours  and  forty-five  minutes.  It  was  then  turned  over  to  the  War 
Department  as  a  school  ship. 

The  next  year  a  new  and  larger  balloon,  equipped  with  a  more 
powerful  motor  was  used.  Many  flights  were  made  in  tests  for  the 


30 


DIRIGIBLE   BALLOONS 


31 


French  War  Department.  In  some  of  these,  the  Lebaudy  Brothers 
were  accompanied  by  the  minister  of  war. 

La  Patrie.  La  Patrie  was  then  built  for  the  French  govern- 
ment by  the  Lebaudy  Brothers,  and  was  of  the  same  design  as 
their  earlier  airships.  In  speed  it  was  nearly  equal  to  Zeppelin's,  and 
its  dirigibility  was  nearly  perfect.  Fig.  9  shows  a  view  of  this  air- 
ship in  flight. 

Jt  was  200  feet  long,  and  the  70-horse-power  engine  drove  two 
propellers.  It  could  carry  seven  people  and  one-half  ton  of  ballast. 
It  carried  four  people  at  a  speed  of  30  miles  per  hour.  On  its  last 


Fig.  9.     La  Patrie,  French  War  Dirigible 

trip  it  covered  175  miles  in  seven  hours.  A  few  days  afterward,  a 
heavy  wind  tore  it  away  from  its  moorings,  and  it  was  blown  out 
to  sea  and  lost. 

La  Republique  and  Le  Jaune.  Two  more  airships  of  the  same 
type,  La  Republique  and  Le  Jaune,  followed  this.  These  were  tried 
by  the  French  government  in  1908,  and  both  proved  successful. 
La  Republique  is  illustrated  in  Fig.  10.  The  shape  and  equipment 
of  the  car  are  shown  in  Fig.  11.  The  automobile-type  radiator  may 
be  seen  attached  to  the  side  of  the  car.  During  a  flight  in  the  fall 
of  1909,  a  propeller  blade  broke  and  was  thrown  clear  through  the 


31 


32 


DIRIGIBLE   BALLOONS 


Fig.  10.     La  Republique,  French  War  Dirigible 


Fig.  11.     Car  of  La  Republique 


32 


DIRIGIBLE   BALLOONS  33 

balloon  envelope,  causing  the  balloon  to  fall  from  a  height  of  500 
feet.  The  four  officers  who  formed  the  crew  of  the  dirigible  were 
instantly  killed. 

The  Russian  government  commissioned  the  Lebaudy  Brothers 
to  build  an  airship  which  was  to  be  the  nucleus  of  the  Russian  air 
navy.  Accordingly,  the  Russie  was  built  early  in  1909,  and  is  a 
faithful  copy  of  the  French  La  Republique  in  every  respect;  a  num- 
ber of  others  have  been  delivered  to  the  Russian  army  since.  Trips 
are  in  progress  at  the  Lebaudy  Airship  Works  at  Moisson. 

Portable  Airship.  For  military  purposes,  an  airship  should  be 
so  constructed  as  to  be  easily  and  quickly  packed.  A  dirigible 
balloon  was  built  in  1908  by  Count  de  la  Vaulx,  which  could  be  very 
easily  taken  apart  for  transportation  and  put  together  again.  The 
fact  that  it  was  capable  of  carrying  only  one  man  was  the  cause  of 
its  limited  usefulness. 

Clement=Bayard  II.  The  numerous  factors  that  must  be 
considered  in  the  design  of  a  successful  dirigible  balloon,  as  well  as 
the  many  conflicting  conditions  that  must  be  reconciled,  have 
already  been  referred  to  in  detail.  How  these  are  carried  out  in  prac- 
tice may  best  be  made  clear  by  a  description  of  what  may  be  con- 
sidered as  an  advanced  type  of  dirigible,  the  Clement-Bayard  II, 
Fig.  12,  of  French  design,  and  the  most  successful  of  the  French 
military  air  fleet.  In  fact,  the  design  of  this  airship  incorporates 
all  those  features  which  the  experience  of  aeronauts  in  other  coun- 
tries, notably  Germany  and  Italy,  has  proved  to  be  best  adapted 
to  aerial  navigation,  and  it  is  said  that  future  additions  to  the  French 
aerial  navy  will  be  patterned  after  this  type.  Its  predecessor,  the 
Clement-Bayard  I,  Fig.  13,  made  thirty  voyages,  some  of  them  of 
considerable  distances,  without  suffering  any  damage,  but  a  study 
of  its  shortcomings  led  to  their  elimination  in  the  following  model. 
The  difference  between  the  two  may  be  realized  by  comparing  the 
illustrations  in  connection  with  the  following  comments  on  the 
changes  made  and  the  reasons  therefor. 

The  pisciform  shape  of  the  first  Clement-Bayard  has  been 
retained,  but  it  has  been  given  more  taper  and  more  grace,  the  dimen- 
sions being  248.6  feet  overall  by  42.9  greatest  diameter,  this  being 
but  a  short  distance  back  of  the  bow.  This  gives  it  a  ratio  of  length 
to  diameter  of  5.76.  The  gas  balloonet  stabilizers  have  been  elimi- 


33 


34 


DIRIGIBLE  BALLOONS 


nated  altogether,  as  will  be  apparent  at  first  glance  at  Fig.  12.  The 
total  gas  capacity  is  approximately  80,000  cubic  feet.  Like  all 
French  dirigibles  it  is  of  the  true  flexible  type,  the  only  rigid  con- 
struction being  that  of  the  framework  of  the  car  itself.  To  the  latter 


Fig.  12.     Clement-Bayard  II,  French  Dirigible 

are  attached  all  rudders  and  stabilizing  devices,  instead  of  making 
them  a  part  of  the  envelope  as  formerly.  The  latter  is  made  of 
continental  rubber  cloth. 

Light  steel  and  aluminum  tubing  are  employed  in  the  construc- 
tion of  the  frame  supplemented  by  numerous  piano-wire  stays. 
This  frame  extends  almost  the  entire  length  of  the  envelope,  and 
carries  at  its  rear  end  a  cellular,  or  box-kite  type  of  stabilizing  rudder, 
instead  of  the  former  gas  balloonets  employed  on  the  Clement- 
Bayard  I,  Fig.  13.  This  cellular  rudder  is  in  two  parts,  consisting 
of  two  units  of  four  cells  each,  the  two  groups  being  joined  at  the 


34 


DIRIGIBLE   BALLOONS 


35 


top,  with  a  space  between  them.  In  addition  to  acting  as  a  stabilizer, 
this  is  also  the  direction  rudder,  its  leverage  being  increased  by  mak- 
ing the  end  planes  somewhat  larger  than  the  partitions  of  the  cells. 
Between  the  cellular  stabilizing  rudder  and  the  envelope  is  placed 
the  horizontal  rudder  for  ascending  or  descending.  In  the  illustra- 
tion this  appears  to  be  a  flag,  but  it  is  in  reality  a  long  rectangular 
plane,  which  may  be  tilted  on  its  longitudinal  axis,  the  latter  being 
at  right  angles  to  that  of  the  balloon.  There  are  two  air  balloonets 


Fig.  13.     Clement-Bayard  I 

of  about  one-third  the  total  capacity  of  the  balloon  itself,  and  they 
are  designed  to  be  inflated  by  large  aluminum  centrifugal  blowers 
driven  from  the  main  engines  themselves. 

There  are  two  motors,  each  of  125  horse-power,  both  being  of 
the  same  conventional  design,  i.e.,  four  cylinder,  four  cycle,  vertical, 
water  cooled.  In  fact,  they  are  merely  light  automobile  motors. 
The  cylinders  have  separate  copper  water  jackets  and  the  motors 
themselves  are  muffled,  which  is  a  departure  from  the  usual  custom. 
Each  drives  a  separate  propeller  carried  on  top  of  the  main  frame 
through  bevel  gearing. 


35 


36  DIRIGIBLE   BALLOONS 

The  Clement-Bayard  II  made  itself  famous  by  its  rapid  and 
successful  flight  from  the  suburbs  of  Paris  across  the  Channel  to 
London,  in  October,  1910.  This  quick  descent  of  one  of  the  repre- 
sentatives of  the  French  "fourth  military  arm"  over  the  erstwhile 
sacred  dividing  line — the  Channel — stirred  the  British  mind,  ever 
on  the  lookout  for  possibilities  "of  foreign  invasion,  to  an  almost 
frenzied  activity  in  aeronautical  affairs.  England  at  once  entered  the 
field  and  built  one  of  the  largest  dirigibles  ever  constructed,  "The 
Mayfly,"  a  huge  airship  of  the  Zeppelin  rigid  type,  which  answered 
the  query  implied  by  its  name,  by  not  flying  at  all,  as  it  was 
wrecked  the  first  time  an  attempt  was  made  to  take  it  out  of  the 
shed,  as  mentioned  farther  along. 

LATER  FRENCH  TYPES 

Zodiac,  Le  Temps,  Astratorres.  After  the  disaster  to  La 
Republique  in  1909,  so  little  activity  was  shown  in  this  field  by 
France  that  the  land  which  had  given  birth  to  the  dirigible  balloon 
seemed  ready  to  discard  what  had  been  a  source  of  considerable 
pride  before  it  was  equaled  and  then  surpassed  by  Germany.  From 
that  time  until  the  middle  of  1911,  only  three  very  small  units  were 
added  to  the  depleted  French  fleet,  the  Zodiac,  Le  Temps  and 
Astratorres,  and  while  these  were  very  efficient  for  their  size  and 
were  much  used  for  training  purposes,  they  made  a  sorry  showing 
compared  to  what  France  had  been  doing  previously.  But  while 
there  was  an  apparent  lack  of  interest  in  this  branch,  a  general 
reorganization  was  actually  being  planned  to  build  a  new  fleet  of 
French  military  dirigibles  capable  of  making  altitudes  of  6,000  to 
7,000  feet,  where  they  would  be  immune  from  any  attack  save  that 
of  aeroplanes  which  could  be  fought  off.  The  scale  on  which  this 
reorganization  is  planned  is  apparent  in -the  amount  of  equipment 
used.  To  the  only  two  airship  sheds  or  "harbors"  exceeding  400 
feet  in  length  previously  to  be  found  in  the  entire  country,  no  less 
than  nine  have  been  added.  All  of  these  are  400  feet  long  and  are 
so  built  as  to  be  readily  enlarged  to  600  feet.  Each  of  these  is  designed 
to  accommodate  two  of  the  big  dirigibles  at  once.  There  are  no  less 
than  six  large  hydrogen  generating  plants  in  France,  one  of  them 
having  a  capacity  of  360,000  cubic  feet  per  day,  and  others  of  similar 


36 


DIRIGIBLE   BALLOONS  37 

size  are  to  be  added.  The  plans  also  include  the  building  of  a  large 
fleet  of  big  airships. 

Lieutenant  Selle  de  Beauchamp.  The  first  squadron  of  the 
new  fleet  consists  of  four  vessels,  the  Lieutenant  Selle  de  Beau- 
champ,  Capitaine  Marechal,  Adjutant  Vincenot,  and  the  Adjutant 
Reau,  all  of  them  having  been  named  after  the  officers  who  per- 
ished in  the  La  Republique  disaster.  Their  type  is  a  clever  develop- 
ment of  the  old  Lebaudy  and  the  Ville  de  Paris,  of  the  classic  La 
France  type,  the  Adjutant  Reau  and  its  sister  ship  being  patterned 
after  the  Ville  de  Paris,  while  the  other  two  are  improved  Lebaudys. 
With  about  250,000  cubic  feet  displacement,  a  length  of  270  feet, 
beam  38  feet  and  a  power-plant  consisting  of  two  80-horse-power 
motors  on  each,  these  are  the  smallest  of  the 'four,  but  the  most 
interesting,  as  the  Lebaudy  type  with  its  single  short  car  does  not 
lend  itself  so  readily  to  enlargement  from  the  engineering  point  of 
view. 

The  outlines  are  strictly  of  the  Lebaudy  type,  but  in  the  Lieu- 
tenant Selle  de  Beauchamp  essential  differences  are  to  be  seen  in 
the  suppression  of  the  vertical  stabilizing  fin  at  the  extreme  stern, 
this  being  replaced  by  fixed  surfaces  forming  part  of  the  vertical 
rudders.  All  rudder  surfaces  are  doubled,  this  feature  making 
possible  a  saving  of  weight  and  representing  standard  practice  on 
all  large  airships  of  recent  construction.  Part  of  the  horizontal 
rudder  planes  are  nearly  amidships,  where  they  act  less  as  rudders 
than  as  true  aeroplanes  lifting  or  depressing  the  ship  to  an  even 
keel.  There  are  two  large  air  balloonets,  each  of  which  is  designed 
to  be  filled  by  a  centrifugal  blower  of  large  capacity.  These  blowers 
are  mounted  directly  below  the  balloon  and  each  one  of  them  is 
driven  from  a  different  motor  through  a  vertical  rope  transmission. 
Either  of  these  blowers  may  be  employed  to  inflate  either 'or  both 
of  the  air  balloonets,  so  that  their  duplication  and  coupling  to  different 
motors  is  a  measure  of  precaution  solely.  The  car  is  supported  on 
a  deep-trussed  frame  of  steel  tubing  suspended  some  distance  below 
the  balloon,  the  propellers  being  mounted  on  tubular  steel  out- 
riggers, while  there  is  a  perfect  maze  of  suspension  ropes  and  trussing 
guys  in  sharp  contrast  with  the  simplicity  of  the  German  dirigibles 
of  either  the  rigid  or  semi-rigid  types.  This  should  not  only  prove 
a  source  of  greatly  increased  head  resistance,  but  likewise  one  of 


37 


38  DIRIGIBLE   BALLOONS 

weakness  and  danger  from  which  an  airship  designed  for  military 
purposes  should  be  free.  A  year  or  two  ago,  the  big  Zeppelin  rigid 
airships  could  not  rise  high  enough  to  be  considered  a  source  of 
danger  from  a  military  point  of  view,  but  now  that  this  type  can 
ascend  to  a  height  of  6,500  feet  and  has  an  effective  radius  of  action 
of  over  600  miles,  together  with  a  nice  regulation  of  ascent  and 
descent,  it  appears  that  the  German  airships  should  be  much  more 
effective.  „ 

GERMAN  DIRIGIBLES 

Zeppelin  Airships.  At  the  same  time  that  Santos-Dumont 
was  carrying  on  his  hazardous  experiments,  the  problem  was  being 
attacked  along  slightly  different  lines  by  a  retired  German  mili- 
tary officer,  Graf  von  Zeppelin,  or  Count  Zeppelin,  as  he  is  usually 
called. 

When  a  mere  boy  he  was  constantly  experimenting  with  air 
craft,  and  succeeded  in  making  small  flights,  at  one  time  falling  50 
feet.  He  was  indomitable  in  his  purpose  to  invent  a  successful  air- 
ship, and  fought  for  his  plans  against  the  disbelief  of  all  those  around 
him. 

It  was  not  until  he  retired  from  the  German  army,  that  the 
Count  gave  up  all  his  time  to  the  construction  of  an  airship.  He 
received  some  aid  from  the  German  government,  but  most  of  the 
fortune  put  into  his  giant  aerial  craft  was"  his  own.  In  fact,  he  spent 
practically  everything  he  had.  Although  he,  like  Santos-Dumont, 
employed  a  machine  of  the  lighter-than-air  type,  the  construction 
of  the  gas  bag  was  radically  different. 

It  will  be  remembered  that  Dumont  experienced  much  trouble 
on  account  of  the  envelope  of  his  balloon  being  too  plastic,  causing 
it  to  crumple  in  the  middle  and  to  become  distorted  in  shape  from 
the  pressure  of  the  air.  His  efforts  to  overcome  this  by  employment 
of  air  bags  did  not  meet  with  great  success,  even  in  his  later  types. 

Construction.  Zeppelin  employed  a  very  rigid  construction. 
His  first  balloon,  which  was  built  in  1898,  was  the  largest  which 
had  ever  been  made.  It  is  illustrated  in  Fig.  14,  which  shows  his 
first  design  slightly  improved.  It  was  about  40  feet  in  diameter 
and  420  feet  long — an  air  craft  as  large  as  many  an  ocean  vessel. 
The  envelope  consisted  of  two  distinct  bags,  an  outer  and  an  inner 


38 


DIRIGIBLE   BALLOONS  39 

one,  with  an  air  space  between.  The  air  space  between  the  inner 
and  outer  envelopes  acted  as  a  heat  insulator  and  prevented  the 
gas  within  from  being  affected  by  rapid  changes  of  temperature. 
The  inner  bag  contained  the  gas,  and  the  outer  one  served  as  a 
protective  covering.  In  the  construction  of  this  outer  bag  lies  the 
novelty  of  Zeppelin's  design.  A  rigid  framework  of  strongly-braced 
aluminum  rings  was  provided  and  this  was  covered  with  linen  and 
silk  which  had  been  specially  treated  to  prevent  leakage  of  gas.  The 
inner  envelope  consisted  of  seventeen  gas-tight  compartments 
which  could  be  filled  or  emptied  separately.  In  the  event  of  the 
puncture  of  one  of  them,  the  balloon  would  remain  afloat.  An 


Fig.  14.     Zeppelin  Dirigible  Rising  from  Lake  Constance 

aluminum  keel  was  provided  to  further  increase  the  rigidity.  A 
sliding  weight  could  be'  moved  backward  or  forward  along  the  keel 
and  cause  the  nose  of  the  airship  to  point  upward  or  downward  as 
desired.  This  would  make  the  craft  move  upward  or  downward 
without  throwing  out  ballast  or  losing  gas.  Under  each  end  of  the 
balloon  a  light  aluminum  car  was  rigidly  fastened,  and  in  each  was 
a  16-horse-power  Daimler  gasoline  engine.  The  two  engines  could  be 
worked  either  independently  of  each  other  or  together.  Each  engine 
drove  a  vertical  and  horizontal  propeller.  The  propellers  each  had 
four  aluminum  blades.  As  will  be  seen  from  Fig.  14,  the  cars  were 
too  far  apart  for  ordinary  means  of  communication  and  so  speaking 
tubes,  electric  bells,  and  an  electric  telegraph  system  were  installed. 


39 


40  DIRIGIBLE   BALLOONS 

First  Trials.  Very  little  was  known  as  to  the  effects  of  alight- 
ing on  the  ground  with  such  a  rigid  affair  as  this  vessel,  therefore 
the  cars  were  made  like  boats  so  that  the  airship  could  alight  and 
float  on  the  water.  The  first  trials  were  made  over  Lake  Constance 
in  July,  1900.  The  mammoth  craft  was  housed  in  a  huge  floating 
shed,  and  the  vessel  emerged  from  it  with  the  gas  bag  floating  above 
and  the  two  cars  touching  the  water.  She  rose  easily  from  the  water, 
and  then  began  a  series  of  mishaps  such  as  usually  fall  to  the  lot 
of  experimenters.  The  upper  cross  stay  proved  too  weak  for  the 
long  body  of  the  balloon,  and  bent  upward  about  10  inches  during 
the  flight.  This  prevented  the  propeller  shafts  from  working  properly. 
Then  the  winch  which  worked  the  sliding  weight  was  broken  and, 
finally,  the  steering  ropes  to  the  rudders  became  entangled.  In  spite 
of  all  this,  a  speed  of  13  feet  per  second,  or  about  9  miles  per  hour, 
was  obtained.  These  breakages  made  it  necessary  to  descend  to  the 
lake  for  repairs  and  in  alighting  the  framework  was  further  damaged 
by  running  into  a  pile  in  the  lake.  The  airship  was  repaired  and 
another  flight  was  made  later  in  the  year,  during  which  a  speed  of 
30  feet  per  second,  or  20  miles  per  hour,  was  obtained. 

Second  Airship.  Zeppelin  had  sunk  his  own  private  fortune  and 
that  of  his  supporters  in  his  first  venture,  and  it  was  not  till  five 
years  later  that  he  succeeded  in  raising  enough  money  to  construct 
a  second  airship.  No  radical  changes  in  construction  were  made  in 
the  new  model,  but  there  were  slight  improvements  made  in  all  its 
details.  The  balloon  was  about  8  feet  shorter  than  the  original  and 
the  propellers  were  enlarged.  Three  vertical  rudders  were  placed  in 
front  and  three  behind  the  balloon,  and  below  the  end  of  the  craft 
horizontal  rudders  were  installed  to  assist  in  steering  upward  or 
downward.  The  steering  was  taken  care  of  from  the  front  car. 

The  most  important  change  was  made  possible  by  the  improve- 
ment in  gasoline  engines  during  the  preceding  five  years.  Where,  in 
the  earlier  model,  he  had  two  16-horse-power  engines,  he  now  used 
an  85-horse-power  engine  in  each  car,  with  practically  the  same 
weight.  In  fact,  the  total  weight  of  the  vessel  was  only  9  tons,  while 
his  first  airship  weighed  10  tons. 

His  new  craft  made  many  successful  flights.  One  was  made  at 
the  rate  of  38  miles  per  hour,  and  continued  for  seven  hours,  covering 
a  total  distance  of  266  miles.  During  the  course  of  the  flight,  Zeppelin 


DIRIGIBLE   BALLOONS  41 

made  a  landing  to  take  on  board  a  representative  of  the  German 
ministry  of  war.  In  one  trial  flight  with  both  motors  in  operation, 
the  airship  easily  outdistanced  the  steamers  on  the  lake.  The  German 
War  Department  finally  took  over  the  aeronaut's  ship  and  plant,  and 
the  government  appropriated  $535,000  to  help  carry  on  the  experi- 
ments. Since  then  Zeppelin  has  built  several  airships,  all  of  the  same 
type,  and  others  are  now  under  way  of  construction. 

They  embody  no  remarkable  changes  in  design,  the  principal 
alteration  being  in  size.  The  latter  type  is  illustrated  in  Fig.  15.  In 
one,  the  gas  bag  was  increased  to  446  feet  in  length  and  it  held  over 


Fig.  15.     A  Zeppelin  Airship  in  Flight 

460,000  cubic  feet  of  gas.  This  gave  it  a  total  lifting  power  of  16 
tons.  With  this,  Zeppelin  made  a  voyage  of  over  375  miles.  He  was 
in  the  air  for  twenty  hours  on  this  trip  and  carried  eleven  passengers 
with  him.  In  August,  1908,  the  Zeppelin  left  its  great  iron  house 
at  Friedrichshafen  and  sailed  in  a  great  circle  over  Lake  Constance. 
This  was  to  be  the  nucleus  of  the  aerial  navy  and  Germany  considered 
herself  the  monarch  of  the  air,  as  Great  Britain  was  the  monarch  of 
the  sea. 

The  next  day,  however,  the  ship  was  destroyed  at  Echterdingen 
in  a  storm.     The  German  people  at  once  came  to  Zeppelin's  aid. 


41 


42  DIRIGIBLE   BALLOONS 

The  government  led  a  subscription  list  with  $125,000.  In  all  $500,000 
was  raised,  and  the  Count  again  started  work  on  a  new  aerial  craft 
which  was  taken  over  by  the  government  and  christened  Zeppelin  I. 
On  March  19,  1909,  the  Zeppelin  I  ascended  with  twenty-six  passen- 
gers and  maneuvered  under  perfect  control  for  an  hour  and  a  half  in 
a  series  of  government  tests.  » 

Longest  Airship  Flight.  Still  another  ship,  the  Zeppelin  II,  had 
been  constructed,  without  the  public  knowing  anything  of  its  com- 
pletion, inflation,  or  of  the  preliminary  tests.  It  suddenly  appeared 
before  the  world  in  a  continuous  flight  of  900  miles.  Count  Zeppelin 
had  not  allowed  a  word  to  be  made  public  relative  to  his  intention  of 
undertaking  an  endurance  trip.  It  was,  however,  commonly  believed 
that  he  intended  to  seize  the  first  favorable  opportunity  to  proceed 
to  Berlin.  On  May  31,  1909,  the  Count  in  his  newest  aeronat 
descended  at  Gottingen  at  noon  after  a  flight  of  thirty-six  hours, 
during  which  he  had  covered  850  miles,  thus  more  than  doubling  the 
best  previous  record  in  aviation  for  both  time  and  distance. 

The  vessel  had  quietly  left  the  floating  shed  on  Lake  Constance 
a  little  after  nine  o'clock  at  night,  with  Count  Zeppelin  himself,  two 
engineers,  and  a  crew  of  seven  men  on  board.  Starting  from  Fried- 
richshafen  in  a  direct  line  towards  Berlin,  the  great  ship  continued 
until  it  reached  the  frontier  of  Saxony,  where  it  was  headed  straight 
for  Leipsic.  On  it  went,  crossing  Halle,  into  the  very  heart  of 
Germany,  as  far  as  the  great  air  harbor  at  Bitterfeld,  where  the 
Parseval  airships  were  stationed  in  the  large  plant  belonging  to  the 
Society  for  the  Study  of  Motor  Aeronautics.  Lack  of  knowledge  that 
such  a  thing  as  an  air  harbor  existed  in  Bilterfeld  led  the  press  of  the 
world  to  make  the  error  that  the  ship  had  failed  to  reach  her  destina- 
tion, which,  it  was  assumed,  must  be  Berlin,  since  the  ship  was  headed 
in  that  direction.  The  airship  after  describing  a  great  circle  at 
Bitterfeld,  turned  again  and  sailed  south. 

Meantime  the  military  authorities  at  Berlin  were  without  advices 
as  to  the  Count's  plans,  but  they  learned  from  private  dispatches  that 
the  airship  was  approaching.  An  enormous  crowd  waited  in  vain  for 
five  hours  in  Berlin  in  the  expectation  of  seeing  Count  Zeppelin  arrive 
in  his  airship.  The  Kaiser  came  all  the  way  from  Potsdam,  waiting 
on  the  moonlit  field  until  ten  o'clock,  before  word  was  received  from 
Count  Zeppelin  that  he  had  turned  back. 


DIRIGIBLE   BALLOONS  43 

The  whole  night  long  the  flight  toward  Friedrichshafen  was 
continued.  In  the  morning  it  was  found  that  a  descent  would  have 
to  be  made  to  replenish  the  supply  of  gasoline.  It  was  decided  to  cast 
anchor  in  a  quiet  valley  which  was  protected  by  a  steep  hill  just  ahead 
of  them.  In  the  descent,  the  airship's  bow  prevented  the  man  at  the 
helm  from  seeing  straight  ahead,  and,  while  the  craft  was  closely 
skimming  this  hill,  a  pear  tree  suddenly  shot  up  in  its  course.  For 
the  first  time  there  happened  in  the  air  what  so  often  happens  on  the 
water — the  ship  was  steered  right  into  the  obstacle.  From  the  ground 
it  seemed  for  a  moment  as  though  the  craft  were  doomed  to  certain 
destruction,  as  it  appeared  to  be  swooping  straight  into  the  trunk. 
When  the  big  ship  hung  for  a  second  and  then  forced  its  way  through 
and  circled  slowly  around  a  cheer  went  up  from  the  relieved  watchers 
underneath.  It  was  found  that  the  bow  was  crushed  and  the  forward 
frame  torn  away. 

In  preparing  for  the  trip  to  Friedrichshafen  from  the  scene  of  the 
accident,  all  the  damaged  portion  was  cut  away  in  front  of  the  forward 
car,  and  the  motor  and  propellers  removed.  The  pointed  bow  of  the 
ship  was  thus  changed  to  a  flat  disk  shape,  but  was  so  covered  with 
cloth  as  to  give  a  slight  suggestion  of  pointed  shape.  A  man  was 
stationed  in  the  passageway  between  the  cars  to  act  as  a  moving 
weight,  thus  assisting  the  rear  planes  to  maintain  the  balance,  as  the 
forward  planes  had  been  destroyed.  The  speed  was  necessarily  slow, 
and  owing  to  the  greatly  diminished  carrying  power,  the  ship  stopped 
for  fuel  while  under  way.  Friedrichshafen  ultimately  was  reached  in 
safety. 

The  airship  in  which  Count  Zeppelin  accomplished  this  flight 
was  448  feet  long  and  had  a  diameter  of  42  feet.  It  was  equipped 
with  two  motors  which  furnished  220  horse-power.  Besides  being 
the  largest  dirigible  in  the  world,  its  claim  for  carrying  capacity  is  as 
yet  uncontested. 

On  June  29,  1909,  Zeppelin  I,  under  command  of  Major  Sperling, 
started  from  Friedrichshafen  to  go  to  its  future  home  port  at  Metz. 
A  breakdown  in  the  engine  room  enforced  a  landing  on  the  plains  not 
far  from  Lake  Constance.  While  the  ship  was  waiting  for  duplicate 
parts  of  machinery  a  heavy  gale  arose,  which  prevented  the  continua- 
tion of  the  voyage  even  after  repairs  were  completed.  For  nearly  a 
week  the  storm-bound  vessel  was  exposed  to  the  violence  of  the 


43 


44  DIRIGIBLE   BALLOONS 

elements,  under  the  open  sky,  without  damage  to  the  craft.  Flight 
was  resumed  on  the  night  of  July  3,  and  Metz  was  safely  reached  on 
the  morning  of  July  4.  The  Zeppelin  HI^  larger  and  more  powerful 
than  its  predecessors,  was  then  being  built.  On  August  27,  it  made 
a  successful  flight  from  Friedrichshafen  to  Berlin. 

Deutschland  I  and  II.  In  honor  of  the  governmental  assistance 
that  made  their  building  possible,  the  later  Zeppelin  aircraft  were 
named  in  honor  of  the  Fatherland.  The  first  of  these  was  the  largest 
airship  that  had  been  built  up  to  that  time  (1910),  but  like  her  prede- 
cessors she  was  found  to  be  more  or  less  cranky,  to  apply  a  marine 
term  by  analogy.  In  other  words  the  maneuvering  ability  of  the 
craft  was  defective.  Also  like  her  predecessors,  her  existence  was  an 
extremely  short  one.  Due  to  the  motors  failing  at  a  critical  moment, 
which  coincided  with  a  lack  of  buoyancy,  the  airship  could  not  be  kept 
afloat  and  as  luck  would  have  it,  this  occurred  over  a  pine  forest  into 
which  the  huge  hulk  sank,  the  envelope  being  impaled  at  numerous 
points  on  the  tops  of  the  trees  and  the  car  and  fittings  being  badly 
wrecked. 

To  provide  greater  lifting  power  for  just  such  emergencies,  the 
hull  of  the  Deutschland  II  was  made  lighter,  permitting  the  trans- 
portation of  a  greater  amount  of  ballast  for  the  same  number  of 
passengers.  In  other  respects,  the  new  airship  was  scarcely  more  than 
a  copy  of  her  predecessor  and  with  no  greater  speed  or  any  better 
maneuvering  qualities.  To  further  provide  against  accidents  of  a 
similar  nature,  special  tests  were  made  over  Lake  Constance  to 
familiarize  the  crew  with  the  exact  amount  of  lifting  and  depressing 
power  obtainable  from  the  propellers  and  rudders  alone.  It  was 
found  that  with  only  two  motors  and  two  propellers  in  action,  the 
new  ship  could  be  raised  by  power  like  an  aeroplane,  from  a  static 
level  of  equilibrium  at  an  elevation  of  2,132  feet  to  4,756  feet.  This 
represents  a  purely  dynamic  lift  of  more  than  two  tons  (4,400  pounds) . 
With  three  motors  and  four  propellers  the  ship  rose  to  5,904  feet, 
adding  nearly  another  ton  of  dynamic  lift  (1,980  pounds).  It 
remained  for  some  time  at  this  level,  carrying  four  passengers,  the 
regular  crew  of  nine,  242  pounds  of  fuel  and  oil,  and  4,400  pounds  of 
ballast.  If  one-half  of  this  ballast  had  been  thrown  overboard,  an 
elevation  of  7,544  feet  could  have  been  reached,  while  still  retaining 
more  than  a  ton  of  ballast  in  reserve.  This  shows  an  astonishing 


44 


DIRIGIBLE  BALLOONS  45 

reserve  of  floating  power  for  the  arrow-like  type  of  Zeppelin  balloons 
under  favorable  conditions,  i.e.,  with  the  motors  intact  and  when 
not  overloaded  with  passengers,  and  it  would  add  greatly  to  their 
value  for  military  purposes.  At  such  heights  they  would  be  immune 
from  artillery  fire.  Despite  their  huge  bulk,  their  diameter  does  not 
exceed  the  spread  of  wing  of  a  Wright  biplane,  which  at  the  same 
height  is  an  almost  invisible  speck,  while  a  Zeppelin  at  the  same 
altitude  looks  like  a  match,  its  lean  shape  making  it  a  poor  target. 
In  the  thin  air,  its  speed  is  increased,  so  that  with  a  favoring  wind, 
even  the  slow  Deutschland  could  make  60  miles  an  hour. 

Although  the  new  Deutschland  was  thus  amply  insured  against 
conditions  such  as  caused  the  wreck  of  its  predecessor,  it  shortly  fell 
a  victim  to  an  odd  and  unforeseen  accident — collision  with  the  shed. 
It  hardly  seems  proper  to  term  such  a  mishap  either  odd  or  unforeseen 
when  it  is  recalled  that  a  majority  of  the  huge  airships  of  recent 
build  have  all  come  to  grief  in  a  somewhat  similar  manner,  i.e.,  in 
being  taken  out  of  or  returned  to  the  shed,  the  breaking  in  half  of 
the  biggest  of  them  all,  the  British  naval  dirigible,  being  a  noteworthy 
case  in  point.  As  in  the  case  of  the  latter,  the  Deutschland  also 
"broke  in  two."  Mishaps  from  apparently  trivial  causes,  resulting 
from  lack  of  experience  in  handling  such  huge  craft,  involve  great 
losses  of  money  and  prestige  when  they  happen  to  a  large  and  costly 
dirigible,  whereas  they  are  almost  negligible  in  the  case  of  the  aero- 
plane. 

Schwaben.  Taking  advantage  of  the  experience  gained  in  the 
building  of  the  two  Deutschlands,  Zeppelin  set  about  building 
another  and  this — the  Schwaben — was  almost  half  completed  at 
the  time  the  second  Deutschland  was  wrecked.  The  new  airship 
was  specially  designed  for  passenger  carrying  and  its  dimensions 
marked  a  decrease  in  the  huge  proportions  that  characterized  its 
predecessors.  The  dimensions  of  the  last  Deutschland  were  499 
feet  length  overall,  diameter  46  feet,  and  with  18  independent  gas 
compartments,  giving  a  displacement  of  667,560  cubic  feet;  whereas, 
the  displacement  of  the  Schwaben  is  634,500  cubic  feet,  on  a  length 
of  462  feet,  the  beam  being  46  feet.  The  envelope  is  divided  into 
only  17  gas  compartments  or  cells.  Numerous  experiments  were 
made  to  improve  the  shape  of  the  hull,  as  the  result  of  which  the 
conical  bow  of  the  Deutschland  was  replaced  by  an  ovoid  shape  in 


45 


46  DIRIGIBLE   BALLOONS 

the  Schwaben.  To  diminish  friction  the  outer  envelope  of  the  new 
ship  was  stretched  over  the  frame  with  extreme  care  so  that  it  is  so 
smooth  and  firm  that  non-technical  observers  have  compared  the 
"solid  hull"  of  the  Schwaben  (swallow)  to  a  man-of-war,  owing  to 
the  gray  color.  To  further  cut  down  head  resistance,  the  time- 
honored  aeroplane  rudders,  fore  and  aft,  were  abandoned — quite  a 
radical  step  as  they  had  always  proved  efficient.  In  their  place,  a 
single  set  was  attached  to  a  more  graceful  single  rudder  frame  at 
the  extreme  rear,  where  they  are  combined  with  vertical  rudders 
and  cleverly  supported  by  stabilizing  fins.  It  was  found  that  by 
this  means,  skin  friction  and  head  resistance  were  cut  down,  steadi- 
ness improved  and  the  efficiency  of  all  the  rudders  wonderfully 
increased,  so  that  the  big  ship  could  make  a  complete  turn  in  a  circle 
of  only  800  feet  radius.  What  was  even  more  surprising  was  the 
fact  that  the  lifting  power  did  not  suffer  by  the  removal  of  these 
lifting  planes,  the  kite  effect  of  the  smooth  cylindrical  hull  compen- 
sating for  their  absence  to  an  extent  that  substantially  increased 
the  floating  power  of  the  Schwaben  as  compared  with  Deutschland 
II,  owing  to  the  greater  speed  of  the  former.  The  lack  of  efficiency 
of  an  aeroplane  surface  with  a  very  small  aspect  ratio,  or  very  long 
in  its  line  of  longitudinal  movement,  as  must  be  the  case  when  attached 
to  a  big  envelope,  is  offset  in  a  dirigible  by  the  small  weight  it  has  to 
bear  dynamically  per  square  foot  of  its  immense  area.  As  the  result 
of  long-continued  experiments  in  the  Zeppelin  laboratory,  the 
Schwaben  was  fitted  with  two-  and  four-bladed  propellers  of  greatly 
increased  efficiency,  while  the  head  resistance  of  their  supporting 
brackets  was  greatly  reduced  by  covering  them  with  cloth  in  the 
form  of  useful  stabilizing  fins.  The  result  of  these  improvements 
was  apparent  in  the  greatly  increased  speed,  the  Schwaben  making 
a  fraction  under  43  miles  per  hour  in  calm  air  in  the  course  of  numer- 
ous trial  trips  carried  out  over  a  measured  stretch  of  railway  line, 
in  both  directions.  As  this  rate  of  travel  is  equal  to  that  of  many 
of  the  large  biplanes  which  have  only  an  effective  speed  of  40  miles 
per  hour,  it  revolutionizes  all  former  ideas  regarding  the  inferiority 
of  the  dirigible  in  this  respect  as  compared  with  the  aeroplane.  With 
only  three  of  the  four  motors  running,  all  previous  dirigible  records 
were  broken  by  making  38  miles  per  hour.  In  a  race  from  Darm- 
stadt to  Frankfort,  the  Schwaben  proved  an  easy  victor  over  a 


46 


DIRIGIBLE   BALLOONS  47 

Euler  biplane.  This  great  improvement  in  speed  has  been  due  not 
alone  to  a  decrease  in  the  head  resistance,  but  likewise  to  the  increased 
efficiency  of  the  motors,  as  after  long  experimenting  with  automobile 
types,  Zeppelin  abandoned  them  and  built  special  engines  in  his 
own  plant  for  the  Schwaben.  Six-cylinder  motors  are  employed 
instead  of  the  fours  previously  employed,  and  their  output  increased 
from  110  to  165  horse-power,  so  that  the  total  driving  power  of  the 
new  ship  is  660  horse-power.  Their  reliability  was  also  greatly 
improved,  so  that  in  over  a  hundred  passenger  trips,  of  which  some 
were  700  miles  long,  the  Schwaben 's  engines  have  never  given  any 
trouble.  The  success  of  the  numerous  passenger  trips  was  not  only 
due  to  the  increased  power  but  also  to  the  perfected  methods  adopted 
of  handling  the  big  ship  at  landings.  Mechanical  docking  devices 
have  been  provided  by  which  the  ship  is  securely  held  until  safe  in 
the  open  air,  before  an  attempt  is  made  to  take  it  into  the  shed. 
A  rail  on  each  side  of  the  shed  runs  far  out  into  the  open  through 
each  of  the  doors  at  both  ends.  Each  length  of  rail  is  made  of  two 
narrow  channel  plates  riveted  together  back  to  back.  Two  sets  of 
rollers  run  on  each  rail,  each  set  bearing  against  the  under  side  of 
the  upper  flanges.  Four  steel  cables  made  fast  to  the  airship's 
frame  are  attached  to  the  four  sets  of  rollers,  or  trolleys,  and  all 
may  be  slipped  simultaneously.  The  two  rails  are  so  far  apart  that 
a  dirigible  lashed  to  them  can  not  be  swayed  if  it  have  sufficient 
lift,  this  being  obtained  by  the  removal  of  the  passengers  and  ballast 
before  pushing  the  ship  into  the  shed,  and  not  taking  them  aboard 
again  until  the  big  craft  is  safely  out  of  the  latter  again  before  start- 
ing a  flight,  which  begins  by  the  simultaneous  release  of  all  the 
hawsers.  But  entering  the  shed  with  a  brisk  wind  blowing  at  right 
angles  to  its  axis  and  to  the  rails  is  still  a  difficult  feat.  In  this  case, 
the  ship  is  halted  in  the  open  over  the  track,  heading  into  the  wind. 
One  of  the  front  cables  is  fastened  to  the  rollers  nearer  the  shed  on 
the  windward  rail.  With  this  set  of  rollers  as  a  fulcrum,  the  ship  is 
worked  around  by  pulling  at  the  rear  end,  steadying  it  along  the 
sides,  and  simultaneously  pulling  the  lee  side  down,  until  it  becomes 
parallel  with  the  rails.  It  is  then  a  simple  matter  to  fasten  the  remain- 
ing cables,  unship  passengers  and  ballast,  and  roll  the  craft  into  its 
house.  Even  with  these  improvements,  the  device  is  still  primitive 
and  depends  upon  the  employment  of  a  large  number  of  men  skilled 


47 


48  DIRIGIBLE  BALLOONS 

in  handling  the  big  aircraft.  Damage  from  accidents  of  this  nature 
has  also  been  further  provided  against  by  strengthening  the  struc- 
ture of  the  ship  itself,  the  cars  and  cabin  being  built  of  corrugated 
aluminum,  while  the  strength  of  the  pneumatic  buffers  under  them 
has  also  been  increased.  Of  equal  importance  to  the  improved 
methods  of  docking  are  the  provisions  for  safely  anchoring  the  huge 
dirigible  in  the  open.  A  safe  anchorage  over  unobstructed  grounds, 
mostly  parade  grounds,  has  now  been  provided  in  most  German 
cities. 

The  holding  device  is  a  development  of  the  method  by  which 
in  the  past  severe  squalls  have  occasionally  been  weathered.  It 
differs  from  the  latter  in  that  the  pivotal  point  around  which  the  ship 
swings  into  the  wind's  direction  is  now  placed  on  the  frame  of  the 
ship  itself,  instead  of  on  the  ground.  Even  with  the  short  single  bow 
cable  formerly  used  successfully,  jerks  wThich  strained  the  frame 
and  the  cable  were  not  entirely  avoided  in  gusty  winds,  too  much 
play  in  the  bow  having  snapped  the  long  cable  and  freed  the  ship  on 
one  occasion,  though  it  did  not  damage  the  frame.  In  place  of  the 
single  cable  there  are  now  four,  giving  greater  safety.  They  are  fas- 
tened to  a  ring  that  swivels  round  a  strong  pin  in  the  reinforced 
framework  and  are  permanently  carried  by  the  ship.  When  anchor- 
ing, their  free  ends  are  made  fast  to  four  heavy  cubes  of  concrete 
embedded  in  the  ground,  and  so  placed  that  the  four  cables  evenly 
radiate  toward  them  from  the  pivot  on  the  bow.  Due  to  its  rigidity, 
the  ship  turns  freely  around  the  apex  of  this  pyramid  of  cables  as 
smoothly  as  a  new  weather  vane.  Unshipping  ballast  at  the  bow 
makes  this  pyramid  very  rigid. 

Plans  have  been  completed  for  the  inauguration  of  an  American 
dirigible  passenger  service  similar  to  that  in  operation  between  the 
cities  of  Berlin  and  Frankfort  during  the  past  two  years.  Airships 
similar  to  the  Schwaben  will  be  employed,  the  route  being  between 
Philadelphia,  Atlantic  City,  and  New  York,  the  stopping  place  in 
the  first-named  city,  which  will  be  the  headquarters,  being  erected 
on  the  roof  of  the  Belle vue-Stratford  hotel.  This  landing  platform 
will  be  190  feet  long  by  62  feet  wide  and  at  an  elevation  of  300  feet 
above  the  ground.  It  is  to  be  finished  with  a  surface  of  sod  and  clay 
similar  to  a  baseball  diamond.  One  round  trip  per  day  will  be  made, 
the  fare  being  the  same  as  in  Germany,  that  is, 


48 


DIRIGIBLE  BALLOONS  49 

Parseval.  Germany  has  adopted  another  type  of  airship,  that 
of  Major  von  Parseval.  His  construction  is  very  different  from 
that  of  his  compatriot,  Zeppelin.  Instead  of  the  rigid  construction  of 
the  latter,  the  Parseval  has  no  rigid  connections  except  between 
the  car  and  the  propeller.  Two  air  balloonets  are  employed,  one 
inside  each  end  of  the  balloon,  the  pumps  being  so  arranged  that 
either  one  can  be  filled  or  emptied  independent  of  the  other,  allow- 
ing the  balloon  to  tilt  upward  or  downward  as  desired  by  the  pilot. 
In  addition,  the  car  itself  is  on  two  rollers  and  can  be  moved  forward 
or  backward  on  two  cables,  thus  placing  the  weight  so  as  to  cause 
the  balloon  to  tilt.  The  surfaces  which  steer  the  balloon  are  blown 
under  pressure.  The  propeller  has  four  blades,  and  is  driven  by  a 
90-horse-power  gasoline  engine. 

The  Parseval's  peculiarity  lies  in  its  propeller.  Instead  of  the 
solid  blades  common  to  other  airships,  there  are  four  strips  of  canvas 
with  weights  at  the  end,  held  rigid  by  centrifugal  force  when  in 
motion,  and  hanging  limp  when  the  ship  is  at  rest. 

The  Parseval  II  was  of  almost  the  same  construction,  and  had 
a  promising  though  short  career.  It  collapsed  ignominiously  on  the 
roof  of  a  villa  after  a  flight  of  over  eleven  hours.  A  new  Parseval 
II  has  been  constructed,  and  stationed  at  the  new  government  air 
harbor  at  Bitterfeld.  It  has  two  motors  with  a  total  horse-power 
of  240. 

Parseval  Sporting  Type.  The  Parseval  flexible  system  having 
proven  such  a  success,  the  makers  (Die  Motor-Luftschiff-Studien- 
gesellschaft,  Berlin)  have  brought  out  the  Parseval  V.  The  original 
intention  was  to  design  a  dirigible  of  the  smallest  dimensions  com- 
patible with  the  system,  and  while,  according  to  theory,  it  would 
have  been  possible  to  reduce  the  dimensions  considerably  more  than 
has  been  the  case,  the  miniature  thus  obtained  would  have  been  a 
mere  toy,  devoid  of  any  practical  value.  The  new  Parseval,  accord- 
ingly, has  been  built  to  carry  three  persons  and  a  sufficient  amount 
of  ballast  for  a  six-  to  seven-hour  run  at  a  speed  of  not  less  than  20 
miles  per  hour.  The  Parseval  V  thus  constitutes  the  smallest  of  its 
class  and  is  mainly  intended  for  the  use  of  private  parties  and  aero- 
nautic clubs.  Its  dimensions  are  129  feet  overall,  maximum  diameter 
25.3  feet,  and  its  displacement  42,000  cubic  feet.  The  envelope  is 
made  of  lined  balloon  fabric  of  a  minimum  strength  of  730  pounds 


49 


50 


DIRIGIBLE   BALLOONS  51 

per  foot,  and  weighing  one  ounce  per  square  foot.  The  balloon  is 
made  up  of  a  number  of  longitudinal  sections,  a  construction  which 
somewhat  reduces  the  fractional  resistance  of  the  surface.  The 
details  of  the  construction  are  illustrated  in  Fig.  16.  It  shows  the 
characteristic  Parseval  shape,  rounded  off  elliptically  in  front  and 
tapering  to  a  slender  point  in  the  rear,  in  other  words,  the  pisciform 
outline  recommended  by  Renard.  A  distinctive  feature  wherein 
it  differs  from  all  others  of  the  same  make  is  that  the  vertical  steering 
is  effected  by  a  horizontal  rudder  located  at  the  head  of  the  balloon 
and  operafed  by  cables  from  the  car,  instead  of  the  usual  balloonets. 
This  has  worked  so  well  in  practice  that  the  little  airship  is  capable 
of  maneuvering  within  a  few  yards  of  the  ground  without  danger. 
A  single  centrally-placed  air  balloonet  fed  by  a  centrifugal  air  pump 
is  provided  to  take  care  of  expansion  and  contraction,  as  well  as 
gas  losses.  To  prevent  excessive  stress  being  placed  on  the  envelope 
a  safety  valve  is  provided  in  the  flexible  pipe  connecting  the  pump 
and  the  air  balloonet.  This  valve  opens  automatically  when  sub- 
jected to  a  pressure  equivalent  to  0.6  inch  of  water,  allowing  suf- 
ficient air  to  escape  from  the  balloonet  to  maintain  the  normal 
pressure. 

The  gas  valve  which  is  located  at  the  summit  of  the  balloon  is 
also  designed  to  operate  as  a  safety  valve,  but  as  it  does  not  operate 
of  its  own  accord  until  a  pressure  in  excess  of  one  inch  of  water  is 
reached,  no  gas  losses  occur  unless  the  expansion  of  the  gas  has 
forced  all  the  air  out  of  the  balloonet.  Both  of  these  valves  may 
also  be  operated  by  cables  leading  to  the  control  board.  The  usual 
"ripping  valve"  is  also  provided  in  the  form  of  a  narrow  strip  of 
balloon  fabric  glued  over  a  long  cut  in  the  envelope.  This  can  be 
ripped  open  in  cases  of  emergency  at  a  moment's  notice.  The 
stabilizing  surfaces  are  of  triangular  outline  and  are  combined 
with  the  direction  rudder  at  the  rear.  They  consist  of  frames  of 
steel  tubing  autogenously  welded  together  and  tautly  covered  with 
light  balloon  fabric,  provided  on  both  sides  with  vent  holes  into 
which  air  is  forced  by  the  movement  of  the  airship  when  in  flight, 
thus  keeping  the  fabric  tight  and  smooth.  Side  and  front  eleva- 
tions of  the  car  are  shown  in  Figs.  17  and  18.  It  is  built  of  steel 
tubing  and  measures  14.75  feet  in  length /by  3.25  feet  high,  being 
2.79  and  2.13  feet  wide  at  the  top  and  bottom,  respectively.  Though 


51 


52 


DIRIGIBLE   BALLOONS 


the  normal  carrying  capacity  is  three,  including  the  pilot,  there  is 
sufficient  accommodation  for  four,  but  as  all  the  controls  are  cen- 
tered at  the  pilot's  stand  forward,  the  airship  can  readily  be  handled 
by  one  man.  The  power  plant  is  compactly  arranged  at  the  rear  of 

the  car.  The  engine  is  a  four- 
cylinder,  25-horse-power  Daim- 
ler motor,  running  at  1,200 
r.  p.  m.  and  using  but  0.54  pint 
of  gasoline  per  horse-power  at 
full  load.  The  flywheel  acts 
both  as  a  fan  and 
a  belt  pulley  for 
driving  the  pumps, 
and  the  radiator  is 
placed  directly  be- 


Fig.  17.     Front  Elevation  of  Parseval  V 


Fig.  18.     Side  Elevation  of  Parseval  V  Showing  Motor  and  Transmission  Gear 

hind  it,  the  main  driving  shaft  passing  through  the  radiator  and 
being  supported  by  an  outboard  bearing  back  of  it.  The  propeller 
is  placed  upon  a  bracket  above  the  motor  and  is  driven  by  a  silent 
chain,  the  two  sprockets  having  a  ratio  of  4  to  1.  The  propeller  is 
of  the  3-bladed  type  with  a  diameter  of  9  feet  9  inches  and  differs 
from  those  of  the  earlier  Parseval  airships  in  that  the  blades  are 
semi-rigid,  being  constructed  on  a  framework  so  pivoted  at  the 
base  of  the  blade  as  to  prevent  the  stresses  upon  the  latter  reach- 
ing a  point  dangerous  to  their  safety.  The  suspension  of  the  car 


DIRIGIBLE   BALLOONS  53 

is  analogous  to  that  of  the  larger  Parseval  types,  except  where  slight 
alterations  were  necessary  owing  to  the  reduced  dimensions,  the  car 
depending  from  the  balloon  by  cables  arranged  in  parallelogram 
form  so  as  to  always  keep  it  hanging  in  a  direction  parallel  to  the 
longitudinal  axis  of  the  balloon.  But  it  is  otherwise  free  to  travel 
back  and  forth  in  a  path  controlled  by  two  idlers  on  sliding  ropes 
running  obliquely  fore  and  aft.  This  arrangement  prevents  any 
accidental  inclination  of  the  balloon  in  starting  due  to  the  thrust 
of  the  propeller,  which  accordingly  always  acts  with  its  driving  point 
located  at  the  center  of  resistance  of  the  airship. 

Gross.  The  Gross  has  also  been  approved  by  the  German 
government.  This  is  a  dirigible  of  the  usual  type  driven  by  two 
75-horse-power  motors. 

The  Gross  II  has  been  recently  built  for  the  Prussian  Aeronautical 
Battalion  under  the  supervision  of  its  commander,  Major  Gross. 
It  is  almost  identical  with  the  Gross  I.  Its  movements  are  kept 
more  or  less  secret,  but  it  frequently  crosses  over  Berlin.  Two 
hangars  or  air  harbors  have  been  constructed  for  the  Gross  I  and 
her  sister  ship. 

Krell  I.  That  it  is  possible  to  build  a  successful  airship  of  the 
imposing  dimensions  of  the  various  Zeppelin  craft  without  the  charac- 
teristic rigid  frame  deemed  indispensable  by  the  latter,  is  shown  by  the 
test  of  the  Krell  I,  which  was  finally  launched  in  the  fall  of  1911,  after 
two  years  had  been  spent  in  its  construction.  All  the  weight  saved 
by  the  elimination  iof  the  rigid  frame  has  been  put  into  additional 
propelling  power,  and  as  the  new  airship  has  almost  as  low  a  head 
resistance  due  to  its  rigging  as  the  Zeppelin,  and  a  total  of  500  horse- 
power, as  compared  with  the  165  horse-power  of  the  first  of  the 
latter  type,  its  speed  is  much  greater.  The  Krell  I  may  best  be 
described  as  a  "non-rigid  Zeppelin."  Its  large  size — 393.7  feet 
long  by  42.65  feet  diameter  with  a  displacement  of  473,739  cubic 
feet — makes  necessary  a  slender-shaped  balloon,  similar  to  that  of 
the  Lebaudy  non-rigid  dirigible,  the  Morning  Post,  previously 
described,  because  even  the  natural  static  pressure  of  the  gas  against 
the  back  of  the  envelope  when  under  way,  due  to  the  greater  "head" 
of  gas  resulting  from  increased  beam,  acts  as  a  stiffener.  This 
clearly  illustrates  how  much  of  its  strength  the  big  Zeppelin  derives 
from  the  pressure  of  the  gas  alone,  quite  independent  of  the  rigidity 


53 


54  DIRIGIBLE   BALLOONS 

of  its  frame.  There  is  the  same  long  passageway  of  triangular  cross 
section  running  the  entire  length  of  the  ship  directly  below  the  bal- 
loon, but  in  this  case,  it  is  made  of  cloth  without  any  stanchions, 
the  only  rigid  part  of  it  being  the  flooring,  though  it  is  said  to  feel  no 
less  solid  than  the  Zeppelin  construction.  This  not  only  provides 
communication  between  the  three  cars,  but  also  houses  the  water 
ballast  tanks  as  well  as  the  fuel  and  oil  tanks,  thus  distributing  the 
load  over  the  entire  length.  The  three  cars  differ  from  those  used 
on  the  Deutschland  in  that  the  pilot's  bridge  has  been  placed  in  the 
center  car,  instead  of  the  forward  one,  thus  permitting  two  motors 
to  be  placed  in  the  latter  and  the  other  two  motors  in  the  after  car. 
The  passengers  are  carried  in  the  center  car.  However,  the  pro- 
pellers being  directly  mounted  on  the  cars  and  not  on  the  flexible 
hull,  thus  avoiding  long  transmissions,  more  propellers  have  been 
provided.  There  are  three  on  each  car,  or  six  in  all.  In  each  of 
the  forward  and  after  cars,  a  125-horse-power  motor  drives  two 
2-bladed  propellers,  mounted  on  outriggers  at  the  sides,  while  the 
other  motor  of  the  same  power  drives  a  single  4-bladed  propeller 
mounted  directly  on  the  elongated  shaft  of  the  motor  extending 
behind  each  car.  These  shafts  are  supported  by  steel  tubing  in 
pyramid  form.  The  two  engine  cars  are  so  far  apart  that  no  inter- 
ference results  from  this  compact  arrangement,  especially  as  the 
center  is  raised  to  the  same  level  as  the  other  two,  following  Zeppelin 
practice  in  this  respect.  The  auxiliary  power  plant  is  carried  in  the 
center  car,  and  as  the  blowers  for  maintaining  the  necessary  pressure 
in  the  air  balloonets  must  naturally  be  large  on  an  airship  of  such 
size,  this  takes  the  form  of  two  25-horse-power  motors.  Only  one 
is  employed,  the  other  being  held  in  reserve.  The  three  cars  are 
only  slightly  lower  beneath  the  hull  than  were  those  of  the  Deutsch-* 
land,  the  short  suspension  cables  being  made  fast  to  the  cloth  sides 
of  the  long  passageway.  But  several  auxiliary  cables  are  also  led 
from  the  cars  directly  to  the  envelope  to  which  they  are  attached, 
as  in  the  Parseval  type,  by  layers  of  bands  or  huge  reinforcing 
"patches"  sewed  to  the  outside  of  the  balloon.  Horizontal  rudders, 
similar  to  those  of  the  Zeppelin,  are  employed,  but  they  are  much 
smaller  and  are  mounted  on  the  sides  of  the  passageway  instead 
of  directly  on  the  balloon.  They  are  placed  above  the  front  and 
rear  cars  and  there  is  also  a  horizontal  propeller,  placed  beneath 


DIRIGIBLE   BALLOONS  55 

the  floor  of  the  center  car,  designed  to  be  driven  by  the  reserve 
motor  in  case  of  emergency.  Communication  between  the  cars 
and  the  passageway  is  by  means  of  ladders,  the  cars  themselves 
being  surrounded  by  a  tubular  framework  resembling  a  cage.  The 
huge  vertical  rudder  is  similar  to  that  of  the  Clement-Bayard  II. 
It  is  like  a  Venetian  blind  with  five  slats  and  is  mounted  just  below 
the  easy  curving  stern,  being  supported  by  a  tubular  framework 
secured  to  the  envelope  at  points  protected  by  reinforcing  patches, 
in  exactly  the  same  manner  as  the  Parseval  construction  of  this 
essential.  The  shape  of  the  hull  is  also  similar  to  that  of  the  Parseval, 
but  it  has  been  elongated  to  such  an  extent  as  to  more  closely  resemble 
the  Zeppelin. 

Veeh  I.  In  contrast  with  all  of  the  German  dirigibles  thus 
far  described,  the  Veeh  embodies  many  of  their  features,  but  at  the 
same  time  differs  radically  from  every  one  of  them.  It  is  of  the 
semi-rigid  type,  but  is  of  such  novel  construction  as  not  to  resemble 
any  of  the  airships  of  this  type  previously  built.  The  frame  is  in 
the  form  of  a  single  girder  extending  the  entire  length  of  the  bal- 
loon, from  the  tip  of  the  bow  to  the  point  of  the  stern.  It  is  in  the 
form  of  a  keel  and  is  built  up  of  light  steel  tubing.  This  results  in 
quite  a  novel  form  of  airship.  As  the  balloon  is  rigidly  connected 
with  the  steel  keel  throughout  its  length,  all  forces  are  well  dis- 
tributed and  the  necessity  of  compensating  for  any  stresses  by  an 
excessive  tension  of  gas  pressure  is  eliminated.  The  envelope  is 
thus  subjected  to  Considerably  less  strain  and  the  risk  of  explosion 
greatly  reduced.  The  rigid  girder  frame  also  permits  of  a  simple 
and  compact  arrangement  of  the  power  plant  and  drive  besides 
affording  a  solid  support  for  the  stabilizing  surfaces  and  the  rudder. 
Two  pairs  of  2-bladed  wood  propellers,  13.2  feet  in  diameter,  are 
driven  by  two  six-cylinder,  150-horse-power  motors  through  triple, 
parallel,  rubber  cables.  The  propellers  are  enclosed  in  light  metal 
cases  to  protect  the  envelope  and  the  passengers  in  case  the  propeller 
should  break  under  the  high  centrifugal  stresses.  The  lateral  rudders 
are  placed  in  the  air  current  developed  by  the  propellers,  which  makes 
them  so  effective  that  the  airship  may  be  turned  practically  on  its 
own  axis.  Both  the  elevating  rudders  and  .the  stabilizing  surfaces 
are  solidly  supported  by  brackets  attached  to  the  steel  keel,  the 
tubular  framework  of  the  latter  being  covered  with  fabric  and  in 


55 


56 


DIRIGIBLE  BALLOONS 


56 


DIRIGIBLE  BALLOONS  57 

part  closed  up  by  panels  of  cloth,  to  cut  down  the  head  resistance. 
These  panels  also  act  as  lateral  stabilizing  surfaces  in  addition  to 
affording  shelter  for  the  passengers.  The  envelope  is  of  metallized 
balloon  fabric  with  a  capacity  of  approximately  9,800  cubic  yards 
and  in  the  form  of  an  elongated  cylinder  with  comparatively  blunt 
ends  of  similar  shape.  It  is  subdivided  into  nine  independently 
dismountable  gas  compartments  and  is  provided  with  two  air  bal- 
loonets,  each  of  about  1,100  cubic  yards  capacity.  The  airship 
measures  248  feet  in  length  and  has  a  spacious  trapezoidal  gondola 
between  the  frame  of  the  keel,  measuring  132  feet  long  by  3.3  feet 
wide  at  the  center.  Inclusive  of  the  frame,  rudder,  stabilizing  sur- 
faces, propellers,  motors  and  drive,  the  total  weight  is  only  3,100 
pounds.  With  a  fuel  supply  sufficient  for  a  10-hour  flight  and  the 
full  complement  aboard,  the  airship  still  has  a  reserve  buoyancy  of 
2,200  pounds.  Skids  and  spring-mounted  wheels  are  provided  below 
the  frame  to  absorb  the  shocks  of  landing.  Owing  to  the  remarkable 
simplicity  of  the  design  and  the  low  cost  of  the  materials  employed, 
the  expense  for  construction  is  comparatively  small. 

BRITISH  DIRIGIBLES 

In  spite  of  the  fact  that  a  great  deal  of  money  has  been  spent 
upon  the  building  of  dirigibles  in  Great  Britain  during  1910  and 
1911,  the  results  have  amounted  to  little  or  nothing,  being  confined 
practically  to  the  short  trips  of  the  Nulli  Secundus  and  the  various 
trials  and  tribulations  that  the  Morning  Post  has  suffered  almost 
every  time  an  attempt  has  been  made  to  fly  her.  The  last-named 
airship  is  a  large  Lebaudy  type  constructed  in  France,  while  the 
former  is  of  British  design  and  construction,  having  been  built  for 
military  purposes.  As  dirigible  standards  go  nowadays,  however, 
the  Nulli  Secundus  is  only  a  third-  or  fourth-rater.  Fig.  19  shows 
the  general  construction  excellently.  It  will  be  noted  that  the 
direction  rudders  are  placed  forward  instead  of  at  the  stern,  as  is 
the  usual  practice.  The  gas  bag  is  provided  with  a  hull  or  keel, 
similar  in  form  to  that  of  a  ship,  and  from  this  is  suspended  the  car. 
At  the  forward  end  and  on  either  side  of  the  keel  is  a  series  of  five 
horizontal  projecting  fins,  by  means  of  which  the  airship's  course 
can  be  deflected  up  or  down.  At  the  stern  and  on  a  level  with  the 


57 


58  DIRIGIBLE   BALLOONS 

bottom  of  the  keel,  is  a  transverse  horizontal  plane  which  forms  an 
additional  rudder  for  use  in  ascending  and  descending.  The  Nulli 
Secundus  has  a  length  of  111  feet  and  a  capacity  of  85,000  cubic 
feet.  She  is  driven  by  two  propellers  run  by  a  single  motor  and  is 
capable  of  carrying  three  persons  at  a  speed  of  20  miles  per  hour. 
Instead  of  employing  the  usual  balloon  cloth  of  cotton  or  silk  com- 
bined with  rubber,  the  gas  bag  is  made  of  eight  layers  of  goldbeaters' 
skin — about  as  expensive  a  material  as  could  well  be  found  for  the 
purpose.  This  is  made  from  the  lining  of  the  digestive  tract  of  cattle 
and  about  60,000  animals  were  necessary  to  furnish  sufficient  for 
the  making  of  this  one  envelope.  Compared  with  the  one  insignificant 
dirigible  of  30,000-cubic-foot  capacity  owned  by  the  United  States, 
the  Nulli  Secundus  takes  on  considerable  importance,  but  when 
judged  according  to  the  standards  set  by  the  Continental  govern- 
ments, she  is  a  negligible  factor.  Two  or  three  of  this  type  have  been 
built  for  British  military  use  and  are  employed  in  training  army 
officers. 

A  huge  British  dirigible  for  naval  use,  and  of  which  much  was 
expected,  was  built  during  the  winter  of  1910 — 191 1 .  In  its  dimensions 
as  well  as  in  its  numerous  special  features  of  design  and  arrange- 
ment, this  monster  was  to  surpass  anything  of  the  kind  that  had  ever 
been  built,  and  its  ability  in  the  air  was  to  be  in  proportion.  Unlike 
previous  British  dirigibles,  the  Mayfly,  as  the  big  ship  was  named, 
was  built  with  a  rigid  frame  similar  to  the  Zeppelin  type.  There 
probably  have  been  few  airships  built  in  any  country  that  involved 
the  expenditure  of  so  much  money  as  this  one,  but  the  only  reward 
of  months  of  labor  and  waiting  was  to  see  her  ignominiously  broken 
in  half  when  an  attempt  was  made  to  take  her  out  of  the  shed. 

AMERICAN  DIRIGIBLES 

United  States  War  Balloon.  At  The  Hague  Peace  Congress, 
the  representatives  of  the  United  States  signed  a  clause  by  which 
she,  of  all  the  first  or  second  rate  powers,  was  debarred  from  using 
airships  as  a  means  of  offensive  warfare.  Yet  the  United  States,  by 
the  purchase  of  the  Baldwin  dirigible  balloon  in  1908,  committed 
herself  to  a  policy  of  maintaining  airships  as  a  part  of  her  military 
equipment, 


58 


DIRIGIBLE   BALLOONS  59 

The  Baldwin  was  the  only  one  of  the  three  aerial  craft  that  ful- 
filled the  government  requirements  during  the  trials  made  that 
summer  at  Fort  Meyer,  Virginia.  Specifications  were  sent  out  by  the 
chief  signal  officer  of  the  army,  inviting  bids  for  a  dirigible  balloon. 
Among  the  proposals  received  was  that  of  Capt.  Thomas  Baldwin, 
and  after  the  official  trials  the  contract  was  awarded  to  him.  He 
delivered  his  airship  in  August,  1908,  and  it  received  the  name, 


Fig.  20.     Captain  Baldwin's  Dirigible,  the  United  States  Army  Dirigible  I 

Dirigible  I.  It  has  ^  length  of  96  feet,  a  maximum  diameter  of  19J 
feet,  a  volume  of  20,000  cubic  feet,  and  is  designed  to  carry  two 
persons.  At  its  official  trial,  it  made  a  maximum  speed  of  nearly  20 
miles  an  hour,  and  remained  in  the  air  for  two  hours,  covering  a 
distance  of  27  miles.  A  general  view  of  the  United  States  army 
airship,  Dirigible  I,  is  shown  in  Fig.  20. 

The  America.*  As  Wellman's  attempt  to  cross  a  stretch  of 
3,000  miles  of  ocean  in  a  dirigible  was  by  far  the  most  ambitious 
undertaking  of  the  kind  ever  attempted,  a  detailed  description  of 
the  airship  and  the  numerous  special  features  designed  to  make  such 
a  lengthy  voyage  possible  will  be  of  interest.  Contrary  to  the  gen- 
eral impression,  this  was  not  the  same  dirigible  in  which  the  unsuc- 
cessful attempt  to  reach  the  North  Pole  from  Spitzbergen  was  made. 

*  Excerpt  from  Chief  Engineer  Vaniman's  detailed  description  of  the  America.    - 


59 


60  DIRIGIBLE   BALLOONS 

The  balloon  itself  measured  228  feet  in  length  overall,  and  had  a 
diameter  through  its  greatest  transverse  section  of  52  feet,  giving 
it  a  lifting  power  of  close  to  12  tons,  or  to  be  exact,  23,650  pounds. 
The  weight  of  the  envelope  alone  exceeded  2  tons,  the  balloon  proper 
being  made  of  a  costly  fabric  composed  of  two  layers  of  silk  and  one 
layer  of  fine  cotton  cloth,  gummed  together  with  rubber.  There 
were  about  4,000  square  yards  of  this  rubberized  cloth  required, 
weighing  approximately  a  pound  to  the  yard,  and  having  a  tensile 
strength  of  100  pounds  to  the  square  inch.  This  combination  was 
adopted  as  the  silk  and  cotton  provide  great  strength  to  resist  the 
internal  and  external  pressure,  while  the  rubber  binder  made  the 
fabric  almost  gas-tight. 

At  the  center  of  pressure,  or  the  greatest  diameter  of  the  balloon, 
the  fabric  was  used  three-ply,  and  the  most  painstaking  care  was 
used  in  every  detail  of  its  construction  to  obtain  the  maximum 
strength  and  at  the  same  time  reduce  the  gas  leakage  to  a  minimum. 
The  seams  were  wide  lapped,  sewed,  and  gummed,  and  extra  strips 
were  glued  over  them  to  cover  the  needle  holes  to  prevent  the  escape 
of  the  gas.  As  the  weight  of  the  balloon  complete  with  its  air  bal- 
loonets,  valves,  and  other  appurtenances  was  4,700  pounds,  it  had 
a  net  lifting  force  of  18,950  pounds.  In  other  words,  the  volume  of 
gas  required  to  inflate  it  was  sufficient  to  carry  its  own  weight  in 
the  air  and  a  load  of  almost  9J  tons  besides.  Although  hydrogen 
gas  has  a  weight  of  only  one-fourteenth  that  of  air,  it  required  more 
than  a  ton  of  it  to  inflate  this  huge  gas  bag  to  its  full  capacity.  The 
manufacture  of  this  quantity  of  gas  was  not  an  easy  or  inexpensive 
operation.  The  plant  to  generate  the  gas  was  made  in  Paris,  shipped 
to  Atlantic  City  in  sections,  and  there  set  up  just  outside  of  the  shed 
housing  the  airship.  More  than  100  tons  of  sulphuric  acid,  60  tons 
of  iron  turnings,  and  hundreds  of  tons  of  water  were  needed  for  the 
process.  Before  being  admitted  to  the  balloon  the  gas  had  to  be 
thoroughly  cleansed  and  purified  to  make  it  as  light  as  possible  and 
eliminate  all  acids  that  might  destroy  the  costly  fabric  of  the  balloon. 
This  was  accomplished  by  " washing"  the  gas,  or  passing  it  through 
water,  and' subsequently  drying  it  by  again  passing  it  through  cylin- 
ders filled  with  coke,  permanganate  of  potash,  and  calcium  of  lime. 
As  pure  hydrogen  is  odorless  and  gives  no  sign  of  its  presence  when 
escaping,  several  gallons  of  oil  of  peppermint  were  used  to  perfume 


60 


DIRIGIBLE   BALLOONS 


61 


it  in  order  to  immediately  detect  leaks.    The  cost  of  inflating  the 
America  exceeded  $5,000. 

Type  of  Construction.  The  type  of  construction  employed  was 
what  is  known  as  the  "semi-rigid"  similar  to  the  Gross  (German) 
dirigible,  i.e.,  a  rigid  suspension  depending  from  a  flexible  gas  con- 
tainer. The  car  measured  156  feet  in  length  and  consisted  of  a  truss 


Fig.  21.     Wellman's  Airship  "America,"  Showing  Arrangement  of  Car 

of  triangular  section,  built  up  of  light  steel  tubing  shown  in  Fig.  21, 
and  more  in  detail  in  Fig.  22.  The  bottom  chord  of  this  truss  was 
a  cylindrical  steel  tank  with  pointed  ends,  75  feet  long,  employed  for 
carrying  the  main  supply  of  gasoline,  and  having  a  capacity  of 
1,500  gallons.  At  the  top  of  the  truss  a  series  of  transverse  brackets 
was  placed,  the  bag  being  attached  to  the  car  by  means  of  rope 
connections  between  the  ends  of  these  brackets  and  a  strong  band, 
or  web,  formed  on  the  envelope  itself.  This  relingue,  as  the  French 


61 


LOMG/TUD/NAL     SECT/ON  OF ' &4G. 
LOCAT/Ort  OF  3ALLONET3     W/TH    VALI/E3 


A/R  T/GHT 

3ULKHEAI} — » 
COT  LEVEL 


LON6/TUD/NAL      SECT/ON 
UFE  BOAT 


PLAN  y/EW  OF 
TMPLE    FLAME  RUDDER 


Fig.  23.     Details  of  Balloonets,  Lifeboat,  Rudders,  etc.,  of  Wellman's  Airship 


63 


64 


DIRIGIBLE   BALLOONS 


term  it,  was  sewed  to  the  fabric  about  ten  feet  below  the  horizontal 
axis  of  the  balloon.  For  an  emergency  descent,  there  was  a  "ripping 
knife,"  Fig.  23,  shaped  like  an  anchor  and  attached  to  a  rope  lead- 
ing to  the  car.  Pulling  this  would  have  cut  the  gas  bag  practically 
in  half.  From  the  gasoline  tank  fore  and  aft,  the  bottom  chord 
consisted  of  tubular  extensions.  To  stiffen  the  gasoline  tank  laterally, 
stays  were  run  from  the  ends  of  the  extensions  to  horizontal  cross- 
pieces  at  the  ends  of  the  tank  and  thence  back  to  the  body  of  the 
tank,  Fig.  22.  Further  reinforcement  was  obtained  by  means  of 
numerous  wire  cable  stays,  the  whole  practically  forming  a  bridge 


Fig.  24.    View  of  Car  Showing  Propellers  and  Canvas  Covering 

which  in  places  was  said  to  be  capable  of  withstanding  a  stress  of  as 
much  as  10  tons.  No  net,  or  hood,  was.  employed  on  the  gas  bag  to 
add  to  its  resistance  in  motion  through  the  air,  the  external  surface 
of  the  balloon  being  as  smooth  and  tight  as  a  drum  head.  The  car 
and  its  machinery  were  attached  to  the  band  on  the  balloon  by  188 
hemp  lines,  attached  at  as  many  points  on  this  band  and  terminating 
in  eyes  from  which  hung  the  cradle  of  suspension  cables  passing  under 
the  car.  The  latter  was  entirely  closed  by  walls  of  canvas  pierced  by 
several  celluloid  windows,  Figs.  24  and  25,  while  several  canvas 
bunks  were  hung  from  the  transverse  braces  directly  beneath  the 
under  side  of  the  gas  bag,  Fig.  22. 


64 


DIRIGIBLE  BALLOONS 


65 


Motive  Power.  The  motive  power  consisted  of  two  engines, 
the  forward  one  of  which  was  a  Lorraine-Dietrich  four-cylinder, 
water-cooled  automobile  motor  rated  at  80  to  90  horse-power  (the 
one  at  the  right  in  Fig.  24)  and  weighing  with  its  radiator  and  equip- 
ment close  to  1,000  pounds.  It  drove  a  pair  of  wood  screws,  12 
feet  in  diameter,  at  500  r.p.m.  The  other,  Fig.  26,  was  an  E.N.V. 
eight-cylinder  aeronautic  motor  rated  at  practically  the  same  power, 
and  driving  a  second  pair  of  screws  10.5  feet  in  diameter  at  a  speed 


Fig.  25.      Close  View  of  Car  Showing  Windows  and  Long  Gasoline  Tank 

of  750  r.p.m.  In  both  cases,  the  screws  were  carried  on  long  shafts 
extending  outboard  and  constituting  extensions  of  the  crank  shafts 
of  the  motors — in  other  words,  they  were  direct  connected.  In  the 
case  of  the  after  pair  of  screws,  they  could  be  utilized  either  to  propel 
the  ship  forward,  as  shown  in  Fig.  24,  or  they  could  be  employed  to 
assist  either  in  its  ascent  or  descent,  due  to  the  fact  that  they  were 
driven  through  the  medium  of  bevel  gearing  at  the  ends  of  the  engine 
shafts  and  could  be  adjusted  so  as  to  exert  their  force  in  any  direction 
included  within  an  arc  of  180  degrees,  Fig.  26.  This  expedient  was 
adopted  to  take  the  place  of  the  stabilizing  planes  usual  in  French 
construction,  or  the  sliding  weight  of  Zeppelin's  airships.  It  was 


65 


66  DIRIGIBLE   BALLOONS 

made  possible  through  the  ingenious  invention  of  Chief  Engineer 
Vaniman.  As  already  mentioned,  the  drive  between  the  shaft  and 
propeller  was  through  miter  gears.  The  shafts  themselves  were 
carried  in  conical  supports  projecting  out  from  the  sides  of  the  car, 
and  these  supports  were  capable  of  being  revolved  through  the 
medium  of  worm  gears  and  hand  wheel.  As  the  propeller  shaft  is 
turned  through  an  angle,  the  gear  it  carries  is  free  to  travel  on  the 
gear  keyed  to  the  power  shaft. 

In  addition  to  these  two  motors,  there  was  also  a  third,  or 
"donkey  engine,"  to  revert  to  marine  parlance.    This  was  a  small 


Fig.  26.     View  of  Rear  Propellers  Set  Horizontally  for  Lifting  the  Airship 

four-cylinder,  vertical,  water-cooled,  gasoline  motor  rated  at  10  to 
12  horse-power.  It  was  intended  for  a  number  of  purposes,  one  of 
the  most  interesting  of  which  was  cranking  the  larger  engines  to 
start  them.  To  accomplish  this,  the  donkey  engine  shaft  was  geared 
to  the  shafts  of  the  larger  motors  by  means  of  clutches  which  auto- 
matically released  as  soon  as  the  large  motor  started.  This  small 
engine  also  served  to  drive  the  pumps  for  inflating  the  air-balloonets, 
the  arrangement  of  the  latter  being  clearly  shown  in  Fig.  23.  There 
were  six  in  all,  four  placed  forward  and  two  aft,  and  all  were 
fed  with  air  from  a  common  duct.  Each  balloonet,  however, 
was  provided  with  its  own  individual  valve,  so  that  the  distribu- 


DIRIGIBLE   BALLOONS  67 

tion  of  the  air  ballast  could  be  controlled  and  the  ship  kept  on  an 
even  keel. 

Accessories.  The  rudder  consisted  of  three  vertical  planes, 
Fig.  23,  the  center  plane  being  broader  than  the  other  two,  which 
were  set  back  a  few  feet  so  that  when  the  rudder  was  turned  sharply 
to  one  side  or  the  other,  the  plane  at  the  inner  side  of  the  turn  would 
neither  come  in  contact  with  the  balloon,  nor  screen  the  center 
plane,  thereby  cutting  off  its  resistance  to  the  air.  The  bunks  already 
mentioned  were  only  in  the  form  of  extra  accommodation,  the  main 
sleeping  quarters  being  in  a  lifeboat  suspended  beneath  the  car, 
Fig.  24,  and  providing  accommodation  for  the  crew  of  six,  consisting 
of  Walter  Wellman,  who  was  responsible  for  the  undertaking,  Melvin 
Yaniman,  chief  engineer,  Murray  Simon,  navigator  (junior  officer  of 
the  steamship  Oceanic),  J.  II.  Irwin,  wireless  telegraph  operator,  and 
two  mechanics.  This  lifeboat,  shown  in  section  in  Fig.  23,  was 
specially  constructed  for  the  purpose  so  that  while  it  had  an  overall 
length  of  27  feet  by  6  feet  beam,  its  total  weight  was  only  1,000 
pounds.  This  was  accomplished  by  making  the  hull  of  layers  of 
mahogany  veneer  and  canvas,  giving  it  the  appearance  of  being  built 
of  solid  wood.  Two  watertight  compartments  were  provided  fore 
and  aft,  and  the  boat  was  self-bailing  so  that  it  could  keep  afloat  in 
the  heaviest  sea.  There  was  no  power  in  the  boat,  but  a  jury  mast 
and  sail  were  carried  along,  together  with  an  ample  stock  of  pro- 
visions and  water,  so  that  in  case  of  abandonment  it  would  be  possible 
to  keep  afloat  foi^  a  considerable  time.  Through  the  center  of  the 
boat  was  an  upright  steel  tube  through  which  the  equilibrator  passed. 

The  wireless  apparatus  of  the  expedition  was  installed  in  a  for- 
ward compartment  of  the  boat  so  that  it  could  be  employed  both 
while  in  the  air  and  after  the  airship  had  been  abandoned.  That 
is,  as  long  as  the  current  held  out.  The  radius  of  action  of  the  instru- 
ments was  about  100  miles,  and  they  were  provided  with  current 
from  a  small  set  of  storage  batteries  kept  charged  by  a  dynamo 
driven  by  the  donkey  engine.  Current  from  this  battery  also  pro- 
vided electric  lights  for  the  car  and  boat.  In  addition  to  this,  there 
was  a  telephone  system  between  the  boat  and  car.  As  it  would 
undoubtedly  be  necessary  to  get  away  quickly  in  case  the  airship 
had  to  be  abandoned  in  an  emergency,  the  boat  was  suspended  on 
special  self -releasing  hooks,  so  that  by  cutting  a  single  rope  it  could 


67 


68 


DIRIGIBLE   BALLOONS 


be  dropped  instantly.  That  this  was  a  ticklish  maneuver  even  under 
very  favorable  conditions  was  shown  by  the  actual  rescue  of  the  crew. 
It  was  rendered  so  by  the  presence  of  the  equilibrator  which 
did  not  act  quite  as  effectively  in  practice  as  its  theory  would  indicate. 
Its  purpose  was  to  take  the  place  of  the  usual  drag  rope  carried  by 
the  ordinary  spherical  balloons  in  drifting.  As  in  view  of  the  tre- 
mendous lifting  power  of  the  America,  it  would  be  necessary  to 
provide  a  drag  rope  of  considerable  weight,  advantage  was  taken 
of  this  to  make  of  the  equilibrator  a  sort  of  automatically  compen- 


Z/AZ: 


C  UNCOUPLED,  AND  L/PTJHG  HARNESS 
CLAMPED  ON  E  WH/CH  AS   HO/-STED  TO 
DOTTED  POS/T/ON  F.TMEtt  L/NE3  CC 
AXE  DECOUPLED.   L/NES  B£  s4/?ETHEN 
UNCOUPLE!?  AND  E  /S  HO/STED  TO  17 
4ND  EMPT/ED  /WTO  MAfN  GASOL/NE 
.  L/NES  BB  BE //YG   RE 'COUPLED 


LOCMM6  MUT-S   ON 
\  EQU/LE&KATOR  CABLE 


S£LE  y<?///7~s5    W/TH 
FELT  PA  OS  TO  EA3E 
F/?/CT/ON  AND  COLL/S/ON 


Fig.  27.      Diagram  Ghowing  Construction  of  Equilibrator  and  Method  of 
Suspending  it  from  the  Car 

sating  balance,  hence  its  name.  In  fact,  it  took  the  place  of  the 
ballast  ordinarily  carried.  To  give  it  sufficient  weight,  it  was  made 
of  30  short  steel  cylinders,  each  of  which  was  convex  at  one  end  and 
concave  at  the  other,  and,  as  is  made  clear  by  the  detail  view,  Fig.  27, 
the  convexity  of  one  tank  seated  in  the  concavity  of  the  next,  forming 
a  sort  of  universal  joint.  This  whole  series  of  tanks  had  longitudinal 
holes  running  through  their  centers  and  were  strung  on  a  heavy  steel 
cable,  or  flexible  wire  rope.  To  prevent  one  tank  from  damaging 


68 


DIRIGIBLE   BALLOONS  69 

the  next  a  felt  packing  was  placed  between  them  and  the  passage 
for  the  cable  through  the  convex  portion  was  flared,  or  bell-mouthed, 
so  that  there  would  be  no  danger  of  shearing  the  wire  rope. 

At  the  end  of  the  series  of  tanks,  a  series  of  40  wood  blocks, 
each  20  inches  long,  was  strung  on  the  cable,  forming  a  sort  of  "rat 
tail"  to  protect  the  lower  end  of  the  equilibrator  by  taking  the  shock 
of  suddenly  striking  the  water.  The  total  length  of  the  equilibrator 
was  330  feet  and  the  steel  tanks  were  utilized  to  carry  an  extra  supply 
of  gasoline.  The  joints  between  these  tanks  made  it  so  flexible  that, 
in  the  space  of  four  tanks,  it  could  be  turned  at  right  angles  without 
injury.  At  its  lower  end,  the  wood  blocks  tapered  from  about  10 
inches  in  diameter,  down  to  4  inches  at  the  extremity.  Owing  to  its 
great  length  it  was  utilized  as  the  antennae  of  the  wireless  outfit,  in 
addition  to  carrying  a  supply  of  fuel. 

The  purpose  of  the  equilibrator  was  to  avoid  the  necessity 
of  carrying  sand  ballast  to  counteract  temperature  changes  and 
eliminate  any  occasion  for  permitting  gas  to  escape.  The  lower 
end  was  designed  to  trail  on  the  water  and  be  supported  by  it  and 
to  guard  against  losing  it  in  stormy  weather,  the  construction  was 
such  as  to  withstand  a  heavy  sea.  This  was  naturally  made  neces- 
sary by  the  fact  that  each  of  the  tanks  with  its  store  of  gasoline 
weighed  about  100  pounds,  making  the  total  weight  in  excess  of  2 
tons.  The  latter  was  really  ballast  with  a  string  attached  to  it, 
for  as  the  balloon  descended  more  of  the  equilibrator  would  rest  on 
the  water  and  a  correspondingly  increasing  percentage -of  its  weight 
would  be  water  borne,  thus  relieving  the  airship  and  increasing  its 
lifting  force  in  proportion.  When  the  balloon  tended  to  rise,  it  was 
first  necessary  to  lift  the  entire  length  of  the  equilibrator  out  of  the 
water  before  its  height  could  exceed  330  feet  in  the  air.  As  soon  as 
this  took  place,  the  entire  weight  of  2  tons  or  more  acted  as  bal- 
last to  prevent  the  balloon  rising  to  a  great  height. 

To  appreciate  the  importance  of  this  arrangement  in  its  bearing 
upon  the  ability  of  the  America  to  stay  in  the  air,  it  is  necessary  to 
realize  what  extremely  variable  atmospheric  conditions  are  met 
with  and  what  their  effect  is  on  the  balloon.  Hydrogen  gas  expands 
or  contracts  4§x  Part  of  its  volume  for  every  increase  or  decrease  in 
temperature  of  1°F.  Gas  within  a  balloon  subjected  to  hours  of 
warm  sunshine  will  store  heat  in  much  the  same  manner  as  a  green- 


69 


70  DIRIGIBLE   BALLOONS 

house  does,  and  when  a  poor  conductor  of  heat  such  as  rubber  is 
present  as  in  the  fabric  of  -America's  envelope,  this  is  accentuated 
as  more  of  the  heat  is  retained  and  the-  gas  accordingly  becomes 
much  warmer  than  the  surrounding  air  outside.  Assuming  that  the 
gas  reached  a  temperature  of  100°  F.  during  the  afternoon,  which 
could  hardly  be  avoided  on  a  bright  day  even  in  Fall,  and  then  dropped 
to  50°  during  the  night,  it  would  involve  a  contraction  equivalent 
to  one-tenth  of  its  volume.  This  represents  an  extreme  case,  but  a 
variation  of  one-twentieth  was  quite  probable.  With  the  America, 
that  would  mean  a  loss  of  approximately  1,200  pounds  of  lifting 
force.  In  other  words,  to  prevent  settling,  an  equivalent  weight 
must  be  subtracted  from  the  load.  Coming  down  would  cause  an 
increase  in  the  atmospheric  pressure,  still  further  contracting  the 
gas,  while  a  rain  storm  might  augment  its  load  by  depositing  any- 
where from  500  to  1,000  pounds  of  water  on  the  4,000  square  feet  of 
surface  presented  by  the  envelope.  Assuming  that  this  has  occurred 
during  the  night  and  that  the  following  day  is  bright,  exactly  the 
opposite  of  these  conditions  will  obtain.  The  sun  will  dry  out  the 
envelope,  expanding  the  gas  until  the  air  is  driven  out  of  the  bal- 
loonets  through  the  automatic  pressure  valves  and  the  lifting  power 
is  greatly  increased.  There  will  then  be  a  strong  tendency  to  rise 
and,  under  ordinary  conditions,  the  only  means  of  counteracting  this 
would  be  to  permit  the  escape  of  gas. 

This  would  reduce  the  sustaining  power  of  the  balloon  during 
the  next  period  of  contraction,  so  that  \vithout  special  means  of 
guarding  against  the  necessity  of  sacrificing  ballast  to  prevent  com- 
ing to  the  earth,  and  gas  to  avoid  getting  too  far  away  from  it,  the 
voyage  would  naturally  be  limited  to  a  very  short  period — not  more 
than  two  or  three  days  at  the  most.  It  would  also  involve  carrying 
a  great  deal  of  ballast,  thus  sacrificing  the  amount  of  fuel  that  could 
be  taken.  Were  the  ship  to  rise  to  any  great  height,  there  would  be 
the  danger  of  coming  down  too  fast  should  the  gas  suddenly  begin 
to  contract,  and  the  momentum  gained  in  descending  from  a  great 
height  could  be  overcome  only  by  relieving  it  of  a  great  deal  of  weight. 

The  equilibrator,  on  the  other  hand,  was  designed  to  maintain 
the  America  between  100  and  200  feet  above  the  water.  The  ballast 
automatically  "thrown  overboard"  when  the  ship  dropped  lower  was 
again  picked  up  when  it  was  needed  and  in  the  same  manner.  This 


70 


DIRIGIBLE   BALLOONS  71 

meant  saving  gas  and  augmenting  the  quantity  of  fuel  that  could 
be  carried,  making  it  possible  to  prolong  the  voyage  from  the  forty- 
eight-hour  limit  otherwise  practicable  to  the  eight  or  ten  days  that 
were  thought  to  be  necessary  to  cross  the  ocean.  In  theory,  the 
device  appeared  to  be  entirely  practical.  As  a  matter  of  fact,  this 
was  not  the  first  time  it  had  been  tried,  having  been  employed  on 
the  original  America,  in  which  Wellman  made  an  attempt  to  reach 
the  North  Pole  a  couple  of  years  previous.  In  this  instance,  the  con- 
ditions were  entirely  different,  one  of  the  chief  requirements  being  an 
ample  supply  of  provisions,  as  the  explorers  might  be  lost  for  several 
months.  The  equilibrator,  therefore,  took  the  form  of  a  long  leather 
tube  which  constituted  the  drag  rope,  and  in  which  the  food  was 
carried.  The  limited  experience  with  it  under  favorable  weather 
conditions  in  the  Arctic  showed  that  it  rode  smoothly,,  and,  being  a 
continuous  body,  it  did  not  offer  any  substantial  resistance  when 
towed.  Unfortunately,  it  dropped  into  the  ocean  within  two  hours 
after  leaving  Spitzbergen,  thus  depriving  the  expedition  of  its  sup- 
plies. This  leather  food  bag  was  the  predecessor  of  the  equilibrator. 

To  cross  the  Atlantic,  what  was  most  needed  was  food  for  the 
motors.  Their  combined  power  only  sufficed  to  drive  the  America 
at  a  speed  of  26  miles  an  hour,  while  one  of  them  could  propel  her 
at  the  rate  of  20  miles  an  hour.  But  as  each  motor  consumed  1,000 
pounds  of  gasoline  per  day,  it  was  intended  to  keep  only  one  in 
operation,  holding  the  other  in  reserve,  and  also  for  emergency  pur- 
poses when  necessary  to  prevent  being  driven  back  by  contrary 
winds.  With  the  above  speed  as  the  basis,  it  would  require  six  days 
to  cross  the  Atlantic  in  a  perfect  calm  or  its  equivalent,  i.  e.,  the 
favoring  winds  of  one  day  neutralizing  the  contrary  air  currents  of 
other  days.  To  allow  ample  margin,  ten  days  travel  was  provided 
for,  thus  making  it  necessary  to  carry  10,000  pounds  of  gasoline,  or 
5  tons.  Of  this  quantity  4  tons  were  carried  in  the  steel  tank  forming 
the  foundation  of  the  car,  and  the  remaining  2,000  pounds  in  the 
equilibrator. 

The  equilibrator  passed  down  through  the  center  of  the  car,  and 
through  a  well  in  the  center  of  the  lifeboat,  as  shown  in  Fig.  22.  It  was 
supported  by  a  pair  of  steel  cables  running  forward  and  another  pair 
running  aft.  To  provide  a  certain  amount  of  flexibility,  sections  of 
Manila  rope  were  introduced  into  the  steel  cables  as  indicated.  To 


71 


72  DIRIGIBLE   BALLOONS 

be  able  to  utilize  the  supply  of  gasoline  in  the  tanks,  a  pair  of  winches, 
Figs.  22  and  27,  were  provided  to  haul  the  upper  pair  of  cables  in, 
taking  the  strain  off  the  lower  pair  so  that  they  could  be  discon- 
nected by  a  number  of  the  crew  let  down  in  a  "bosun's  chair."  The 
uppermost  tank  was  then  hoisted  and  the  cables  made  fast  again 
below  it.  Then  the  upper  cables  were  slackened  and  detached  to 
permit  of  drawing  the  tank  up  into  the  car.  Contrary  to  what  might 
appear  to  take  place,  in  pulling  in  on  the  winches,  the  equilibrator 
would  not  be  hoisted  but  the  airship  drawn  down. 

In  the  forward  end  of  the  car  was  placed  the  navigator's  bridge, 
where  the  compass,  leeway  indicator,  and  the  steering  wheel  were 
placed,  the  latter  being  connected  by  light  steel  cables  to  the  triplane 
rudder  of  steel  tubing  and  canvas.  Here  also  were  placed  the  meteoro- 
graph, an  instrument  to  record  combined  atmospheric  phenomena, 
the  barograph  (altitude  recorder),  and  the  thermograph  (recording 
thermometer),  as  well  as  the  statoscope  (a  form  of  aneroid  barometer 
having  a  large  air  reservoir  and  highly  responsive  to  minute  fluctua- 
tions in  pressure).  Speaking  tubes  led  aft  to  the  engine  room.  The 
problem  of  navigating  the  ship  was  naturally  no  easy  matter.  While 
its  position  would  be  ascertained  from  time  to  time  in  the  usual 
manner,  by  the  aid  of  the  sextant  and  chronometer,  its  actual  course 
at  any  time  would  be  hard  to  determine.  For  instance,  if  it  were 
traveling  east  at  20  miles  an  hour,  and  the  wind  were  blowing  south 
at  the  same  speed,  its  actual  course  would  be  southeast,  although 
the  compass  indication  would  be  east.  Wind  vanes  or  similar  instru- 
ments would  be  of  no  assistance  as  they  would  have  no  connection 
with  the  sea  as  a  basis  from  which  to  determine  the  direction  of 
motion,  though  this  could  be  obtained  by  means  of  a  log  line  let 
down  from  the  lifeboat.  As  it  was  not  desired  to  reach  any  par- 
ticular port,  there  was  no  great  necessity  for  accuracy  in  navigation, 
the  only  aim  being  to  get  across  the  ocean. 

Akron.  It  was  with  no  feeling  of  regret  that  Melvin  Vaniman, 
leaning  over  the  tafTrail  of  the  steamer  Trent,  watched  the  ill-fated 
America  sink  slowly  to  the  sea.  It  might  be  supposed  that  the 
engineer  who  had  spent  so  many  years  of  work  on  this  dirigible 
would  entertain  some  sentimental  regard  for  the  old  balloon.  But 
Vaniman's  thoughts  were  already  centered  on  another  expedition 
in  which  he  would  not  be  hampered  with  old  material,  an  old  gas  bag 


DIRIGIBLE   BALLOONS  73 

and  old  engines,  but  could  plan  an  entirely  new  airship  made  of  brand 
new  material  and  exactly  as  he  wanted  it.  The  America  had  served 
its  purpose  well,  and  from  her  the  lessons  had  been  learned  that  were 
necessary  to  make  a  future  airship  successful. 

When  the  America  was  abandoned,  it  was  structurally  sound, 
showing  that  the  principles  involved  were  correct.  One  part  only 
had  failed :  A  key  worked  loose  in  one  of  the  propellers,  as  already 
described,  depriving  the  airship  of  the  use  of  the  horizontal  pro- 
pellers, and  to  this  defect  Vaniman  attributed  the  failure  of  the 
expedition.  Contrary  to  public  opinion,  Vaniman 's  faith  in  the 
equilibrator,  or  its  equivalent,  was  not  shaken.  Its  action  in  the 
sea,  its  defects  and  good  qualities  were  all  known  after  this  voyage, 
and  it  was  from  this  experience  that  he  got  to  the  heart  of  the  prob- 
lem, viz,  the  designing  of  a  device  that  would  serve  the  purpose  of 
the  old  equilibrator  without  the  latter 's  defects — a  device  that 
would  have  changeable  and  not  a  fixed  weight,  in  other  words,  an 
equilibrator  that  could  be  made  heavy  or  light  at  will. 

The  new  expedition  has  been  financed  by  F.  A.  Sieberling, 
president  of  a  large  rubber  goods  manufacturing  concern,  and  the 
envelope  of  the  Akron  was  made  in  the  Ohio  city  after  which  it  is 
named,  under  Vaniman's  personal  direction.  It  differs  considerably 
from  that  of  the  America,  being  much  longer  and  of  smaller  diam- 
eter, Fig.  28,  with  a  tapering  stern,  instead  of  the  former  blunt- 
nosed,  double-ended  form.  The  old  hangar  at  Atlantic  City  was 
impressed  into  servjce  again,  but  the  268-foot  length  of  the  new  ship 
exceeded  its  housing  capacity  by  10  feet,  and,  rather  than  enlarge 
the  building,  which  could  have  been  done  only  at  considerable 
expense,  this  much  of  the  balloon  was  sacrificed,  the  dimensions 
of  the  latter  thus  being  258  feet  overall,  by  47  feet  in  diameter. 
Below  the  balloon  is  suspended  a  car  similar  in  shape  to  that  of  the 
America,  but  considerably  longer.  The  body  of  this  car  forms  a 
steel  tank  capable  of  carrying  5  tons  of  gasoline,  and  on  this  tank 
a  platform  constituting  the  floor  of  the  car  is  built.  To  drive  the 
airship,  three  engines  are  provided,  one  of  100  horse-power,  placed 
forward  and  fitted  with  two  propellers  adapted  to  revolve  only  in  a 
vertical  plane,  and  two  others  of  100  and  80  horse-power,  respectively, 
farther  aft.  These  two  motors  are  fitted  with  propellers  which  may 
be  revolved  at  any  angle  between  the  vertical  and  horizontal  planes, 


73 


74 


DIRIGIBLE   BALLOONS  75 

being  adjustable  through  an  arc  of  180  degrees  by  the  aid  of  a  bevel 
driving  arrangement  similar  to  that  on  the  America,  and  designed 
to  enable  the  thrust  of  these  propellers  to  be  utilized  for  raising  or 
lowering  the  airship.  Normally,  only  the  forward  motor  will  be 
employed  to  drive  the  ship  ahead  and,  from  the  results  of  the  short 
trial  trips  made,  there  seemed  to  be  no  reason  for  believing  that 
the  speed  of  30  miles  an  hour  for  which  the  ship  was  designed  when 
running  under  this  one  motor,  would  not  be  realized.  LTnder  full 
load,  this  motor  consumes  about  60  pounds  of  gasoline  per  hour,  so 
that  the  supply  of  5  tons  should  last  a  week. 

When  utilizing  the  forward  motor  alone  for  driving,  the  pro- 
pellers of  the  other  two  motors  will  be  feathered,  or  adjusted  hori- 
zontally so  as  to  present  the  minimum  surface  to  the  wind,  thus  keep- 
ing down  the  head  resistance.  In  addition  to  the  engines  in  question, 
there  is  also  a  17-horse-power  motor  directly  coupled  to  a  dynamo 
to  supply  electric  current  for  lighting  and  for  the  Marconi  wireless 
equipment,  Fig.  28.  It  also  operates  the  blower  for  filling  the  air 
balloonets  and  drives  a  countershaft  from  which  any  of  the  larger 
engines  can  be  started  by  power.  Two  of  the  larger  motors  are  of 
the  six-cylinder  type,  the  other  being  an  eight-cylinder,  while  the 
auxiliary  motor  is  a  four.  Benefiting  from  the  experience  on  the 
America,  the  envelope  of  which  was  in  constant  danger  of  being  set 
afire  from  the  exhaust  of  the  motors,  the  engines  of  the  Akron  are 
equipped  with  specially-designed  mufflers  attached  directly  to  the 
manifold.  One  of  them  is  fitted  with  an  oven  for  use  in  cooking,  Fig.  28. 

Substitute  for  the  Equilibrator.  According  to  Vaniman  the  crux 
of  the  problem  lies  in  the  ability  to  keep  the  airship  down  at  a 
moderate  level.  It  is  an  easy  matter  to  design  an  airship  that  will 
have  sufficient  carrying  capacity  to  cross  the  Atlantic,  but  the  dif- 
ficulty is  to  maintain  the  airship  at  a  constant  moderate  elevation 
above  the  water  during  the  voyage.  The  equilibrator  having  failed 
signally  to  do  this  in  accordance  with  its  theoretical  promises,  it 
has  been  abandoned,  and  the  height  of  the  Akron  is  designed  to  be 
controlled  by  taking  on  water  ballast;  also  by  the  use  of  stabilizing 
planes  fore  and  aft,  while  in  case  of  emergency,  the  elevating  and 
depressing  propellers,  which  have  been  doubled  in  number  and 
power,  can  be  resorted  to.  As  shown  by  the  sketches,  Fig.  28, 
there  are  three  planes  on  each  side  of  the  car,  those  forward  being 


75 


76  DIRIGIBLE   BALLOONS 

curved  upward,  thus  constituting  depressing  planes,  while  those 
at  the  rear  are  curved  downward  and  are  designed  to  be  employed 
as  elevators.  The  latter  are  mounted  on  the  rudder.  These  planes 
may  be  tilted  to  any  angle  desired  and  serve  to  keep  the  airship  on 
an  even  keel.  When  dipping  down  to  take  water,  the  forward  planes 
will  be  used  for  depressing  the  bow,  and  the  rear  planes  for  elevating 
the  stern.  These  planes  are  separately  controlled  by  hand  wheels 
on  either  side  of  the  binnacle,  as  shown  in  the  detailed  sketches  of 
the  steering  gear  in  Fig.  28.  The  level  of  the  ship  may  further  be 
controlled  to  a  considerable  extent  by  inflating  the  balloonets  for- 
ward at  the  expense  of  those  in  the  rear,  when  it  is  desired  to  make 
the  bow  heavier  than  the  stern,  and  vice  versa.  To  scoop  up  water 
ballast,  it  will  be  necessary  to  drive  the  ship  down  near  the  level  of 
the  ocean,  which  may  be  done  by  tilting  either  pair  of  adjustable 
propellers  to  the  proper  angle.  The  only  object  in  having  two  sets 
of  adjustable  propellers  is  to  provide  an  extra  set  for  reserve.  The 
device  with  which  water  ballast  is  scooped  up  is  somewhat  similar 
to  the  equilibrator  used  by  Wellman.  It  consists  of  tanks  about  6 
inches  in  diameter  and  24  inches  long,  strung  upon  cables  exactly 
as  were  the  gasoline  tanks  of  the  equilibrator,  Fig.  28.  These  ballast 
tanks  are  provided  with  openings  near  the  upper  end  of  each  so  that 
by  dragging  them  in  the  sea,  they  will  scoop  up  water.  There  will 
be  three  sets  of  tanks  strung  on  separate  cables,  and  under  normal 
conditions  they  will  not  hang  from  the  car  as  did  the  equilibrator, 
but  will  be  stored  in  the  body  of  the  vessel.  When  taking  up  water 
for  ballast,  if  the  wind  be  strong,  the  airship  will  be  headed  into  the 
wind  and  the  tanks  will  be  trailed  from  a  point  aft'  of  amidships,  so 
there  will  be  no  tendency  for  the  airship  to  nose  down  into  the  sea. 
It  is  planned  to  maintain  the  Akron  at  an  elevation  of  between  200 
and  1,000  feet  at  the  outset  of  the  voyage,  but  as  the  airship  is 
lightened  by  the  consumption  of  gasoline  and  provisions,  it  may 
rise  to  much  greater  heights.  During  the  daytime,  it  will  have  to  be 
heavily  water-ballasted  in  order  to  hold  down  to  these  levels  when 
the  gas  in  the  balloon  is  expanded  by  the  heat  of  the  sun.  At  night, 
this  ballast  will  be  emptied  overboard  to  compensate  for  contrac- 
tion and  the  consequent  reduced  lifting  capacity  of  the  balloon. 

Suspended  below  the  Akron  is  the  same  lifeboat  in  which  the 
crew  of  the  America  made  their  escape,  but  its  construction  has 


76 


DIRIGIBLE   BALLOONS  77 

been  materially  altered  to  facilitate  launching  as  well  as  the  greater 
comfort  of  the  crew.  The  well  in  the  center  has  been  eliminated 
as  there  is  no  longer  any  equilibrator  to  pass  down  through  it.  A 
much  larger  wireless  equipment  with  a  sending  range  of  500  miles 
is  also  installed  in  the  boat,  a  ground  being  provided  by  trailing  a 
wire  in  the  sea.  The  crew  of  the  Akron  numbers  seven  men  all 
told,  consisting  of  the  commander,  navigator,  helmsman,  wireless 
operator,  two  engineers,  and  one  extra  man  for  general  work.  Pro- 
visions are  carried  for  a  cruise  of  twenty  days.  The  original  inten- 
tion was  to  start  in  October,  1911,  but  so  many  causes  of  delay  arose 
that  the  Akron  was  not  ready  for  its  first  trial  trip  until  November. 
Several  trial  trips  were  made,  one  or  two  of  which  were  marred  by 
slight  accidents,  though  generally  successful,  so  that  it  was  decided 
to  postpone  the  start  until  the  following  spring. 

The  navigation  of  a  dirigible  is  a  much  more  difficult  thing  than 
that  of  a  steamer,  as  both  the  speed  and  the  direction  of  travel  are 
more  or  less  uncertain.  Had  it  not  been  for  the  equilibrator  dragging 
in  the  water,  the  crew  of  the  America  would  not  have  known  that 
she  was  traveling  broadside  on,  after  the  motors  were  finally  stopped 
for  good,  nor  how  fast  they  were  going.  In  fact,  as  the  dirigible 
without  its  motors  is  simply  an  old-type  balloon  that  drifts  with 
the  wind  as  if  it  were  a  part  of  it,  there  is  no  sensation  of  movement 
whatever  and  naturally  none  of  direction  when  over  the  open  sea, 
for  want  of  fixed  objects  to  use  as  points  of  observation.  In  this 
connection,  Vaniman  has  devised  a  number  of  interesting  instru- 
ments which  will  indicate  the  direction  of  travel  and  likewise  the 
speed  of  the  airship.  One  of  these  consists  of  a  combined  cameFa 
and  compass,  the  camera  having  its  ground  glass  divided  into  equal 
squares.  By  noting  how  long  a  "fixed  object"  on  the  water  below 
takes  to  pass  across  a  given  number  of  squares,  in  connection  with 
the  altitude  as  indicated  by  the  barometer,  it  will  be  possible  to  cal- 
culate definitely  by  means  of  triangulation  the  speed  at  which  the 
vessel  is  traveling,  and,  by  reference  to  the  compass,  the  direction 
of  travel.  At  first  sight,  it  would  seem  as  if  this  method  would  fail 
for  want  of  a  fixed  object  to  observe,  but  it  will  be  recalled  that 
though  waves  travel,  the  water  that  forms  them  is  practically 
stationary.  Hence,  the  foam  of  a  white  cap  may  be  considered 
as  practically  a  stationary  object  while  it  lasts.  In  addition, 


77 


78  DIRIGIBLE  BALLOONS 

Vaniman  has  also  developed  a  special  type  of  sextant  for  use  on  the 
expedition. 

"Wire-Wound"  Fabric.  The  fabric  employed  in  the  making 
of  the  envelope  of  the  Akron  is  said  to  be  the  strongest  ever  employed 
for  the  purpose,  so  that  by  continually  pumping  air  into  the  balloonets, 
air  ballast  can  be  added  and  the  ship  brought  down  from  a  consider- 
able height.  The  value  of  this  feature  was  strikingly  shown  in  one 
of  the  trial  frips  when  the  airship  was  brought  down  in  this  manner 
from  a  height  of  2,000  feet,  after  an  accident  to  one  motor  and  the 
breaking  of  the  propeller  shaft  of  another. 

This  powerful  control  over  the  gas  led  Vaniman  to  make 
a  further  study  of  the  subject  and  he  calculated  the  strength  of  a 
fabric  necessary  to  resist  the  increased  pressure  in  the  envelope  due 
to  a  rise  in  temperature  of  50  degrees  F.  With  only  a  small  factor  of 
safety,  it  was  found  that  the  tensile  strength  necessary  was  1,000 
pounds  to  the  square  inch,  or  18  tons  to  the  yard.  To  obtain  this 
increased  strength,  a  special  fabric  interwoven  with  fine  piano  wire 
must  be  employed,  the  wires  running  longitudinally  and  circum- 
ferentially  without  cuts  or  joints,  so  that  their  maximum  tensile 
strength  may  be  relied  upon,  the  longitudinal  wires  being  spaced 
rV  inch  and  the  circumferential  wires  A  inch  apart.  This  fine  mesh 
renders  the  envelope  both  fireproof  and  lightning-proof  on  the  prin- 
ciple of  Davy's  safety  lamp,  while  this  great  wire  cage  will  doubtless 
serve  as  an  excellent  antenna  for  wireless  work.  On  an  airship  of  the 
Akron's  size,  the  increased  weight  due  to  the  wrire  is  about  2|  tons. 

The  additional  weight  of  the  wire  would  reduce  the  net  lifting 
power  of  a  ship  of  this  size  from  7J  tons  to  5  tons,  but  the  advant- 
age's obtained  would  warrant  the  sacrifice.  In  comparison  with  the 
weight  of  the  rigid  dirigible  construction,  this  net  carrying  capacity 
is  remarkable.  The  latest  Zeppelin  built  in  1911,  the  Schwaben, 
with  680,000  cubic  feet  of  gas,  has  a  net  lifting  capacity  of  2J  tons, 
while  a  ship  of  the  size  of  the  Akron  with  a  steel-reinforced  gas 
bag  holding  only  400,000  cubic  feet  of  gas  would  have  a  net  capacity 
of  5  tons.  The  ability  of  the  "wire-wound"  envelope  to  withstand 
such  heavy  pressures  would  automatically  take  care  of  the  great 
problem  of  expansion  and  contraction,  giving  a  powerful  control  by 
enabling  the  pilot  to  change  altitude  without  loss  of  gas  or  ballast 
and  without  depending  upon  planes  or  motive  power. 


78 


DIRIGIBLE   BALLOONS 


79 


Vaniman  plans  to  build  a  dirigible  of  the  size  of  the  Akron, 
using  this  new  "wire- wound"  fabric  during  1912. 

Inflating  the  Akron.  As  the  new  Vaniman  airship  has  a  capacity 
of  400,000  cubic  feet  of  gas,  no  small  problem  was  involved  in  the 
manufacture  of  sufficient  pure  hydrogen  gas  to  properly  inflate  it, 
as  the  lifting  power  of  the  gas  is  not  alone  proportional  to  its  purity, 
but  the  presence  of  acid  fumes  or  other  adulterants  would  be  ruinous 
to  the  fabric  of  the  envelope  and  particularly  to  the  numerous  seams. 
To  carry  out  this  important  undertaking  a  special  plant  was  built 
just  outside  of  the  big  shed  at  Atlantic  City.  Making  allowance  for 
waste  and  condensation,  sufficient  material  was  purchased  to  manu- 


Fig.  29.     Plan  View  of  Vaniman's  Hydrogen-Generating  Plant 

facture  450,000  cubic  feet  of  hydrogen.  This  consisted  of  80  tons 
of  scrap  iron  and  100  tons  of  sulphuric  acid.  It  will  be  noted  that 
Vaniman  has  introduced  a  number  of  innovations  in  this  gas 
plant,  as  compared  with  the  usual  method,  so  that  there  is  no  inter- 
ruption in  the  generating  process.  As  shown  in  the  plan  view, 
Fig.  29,  there  are  four  generator  tanks  A,  made  of  wood  with  all 
iron  parts  well  coated  with  pitch  to  prevent  their  being  attacked  by 
the  acid.  These  tanks  are  partly  filled  with  scrap  iron,  Fig.  30.  The 
sulphuric  acid  is  fed  from  one  of  the  two  large  reservoirs  B,  Fig.  29. 
Running  over  these  reservoirs  is  a  track  C,  on  which  the  sulphuric 


79 


80 


DIRIGIBLE   BALLOONS 


acid  casks  D  are  supported.  To  prevent  too  rapid  generation  of 
gas  and  the  choking  of  the  tanks  with  ferrous  sulphate,  the  acid  is 
diluted  in  the  proportion  of  one  part  to  eleven  parts  water.  While 
this  mixture  is  being  prepared  in  one  of  the  reservoirs  the  supply  is 
drawn  from  the  other.  This  solution  takes  the  course  indicated  by 
the  arrows  to  the  bottom  of  the  generator  tanks,  and  it  may  be 
caused  to  flow  directly  into  any  one  of  these  tanks  or  from  one  pair  of 
tanks  to  the  other,  this  being  a  more  economical  method  as  it  insures 
complete  utilization  of  every  bit  of  the  acid.  The  gas  generated  in 
the  tanks  rises  to  the  top,  where  it  is  trapped  by  the  gasometers  E 


Fig.  30.      Side  View  of  Vaniman's.  Hydrogen-Generating  Plant,  Somewhat 
Distorted  to  Bring   Purifying  Tanks  into  View 

and  flowing  into  a  common  chamber  F  passes  down  to  the  washer 
G,  Fig.  30.  Here  it  is  forced  to  pass  upward  through  a  series  of 
perforated  plates,  while  a  spray  of  water  flows  downward  through 
the  same  plates.  Thence,  the  gas  passes  through  four  tanks  H, 
the  first  containing  coke,  the  second  potassium  permanganate,  the 
third  caustic  soda,  and  the  fourth  calcium  chloride.  The  first  two 
serve  to  purify  the  gas  of  such  materials  as  arsenic,  sulphur,  and 
phosphorus  which  are  likely  to  be  picked  up  from  the  iron.  The 
other  two  tanks  serve  to  remove  all  traces  of  moisture  from  the  gas. 


80 


DIRIGIBLE  BALLOONS  81 

Hydrogen  is  an  odorless,  colorless  gas  and  it  would  be  impossible 
to  detect  leaks  in  the  balloon  were  not  some  means  employed  to 
impart  an  odor  to  the  gas.  The  "perfume"  commonly  used  is 
muronine.  This  is  placed  on  a  sponge  in  the  pipe  7,  and  thence 
the  gas  is  fed  directly  into  the  balloon  at  the  tube  J.  The  substance 
in  question  has  a  most  penetrating,  sickish  odor  that  can  be  readily 
detected,  no  matter  how  small  the  leak  may  be. 

One  of  the  advantages  of  the  arrangement  of  this  plant  is  that 
when  it  is  desired  to  charge  one  of  the  generators  with  fresh  scrap 
iron,  it  may  be  cut  out  of  the  system  completely  by  shutting  the 
valve  in  its  connection  and  by  clamping  the  rubber  hose  connecting 
the  gasometer  of  that  particular  generator  with  the  chamber  F. 
The  spent  solution  flows  from  the  generators  through  traps  K  to  a 
trough  L,  which  leads  to  a  large  drain.  Heretofore,  the  purifying 
and  drying  tanks  have  been  filled  with  coke  on  which  the  various 
cleansing  chemicals  were  sprinkled,  the  purpose  of  the  coke  being 
to  prevent  the  materials  from  clogging.  This  method  has  caused 
much  trouble  as  the  materials  would  slowly  gravitate  to  the  bottom 
of  the  tank,  choking  the  flow  of  gas.  Whenever  such  a  condition 
arose,  it  was  necessary  to  shut  down  the  entire  plant  and  clean  out 
the  tanks.  Vaniman  employs  instead  a  set  of  trays  of  copper 
netting  secured  to  iron  straps,  as  indicated  at  M  in  Fig.  30, 
and  on  these  trays  the  purifying  and  drying  materials  are  placed. 
Thus  the  mass  is  kept  in  a  porous  condition,  through  which  the 
gas  can  easily  percolate,  and,  in  case  of  any  trouble,  the  entire  set  of 
trays  can  be  lifted  out  bodily.  It  was  necessary  to  operate  the 
plant  for  five  days  and  nights  continuously,  the  hydrogen  weighing 
more  than  a  ton,  or  about  half  as  much  as  that  of  the  three-ply  cotton 
and  rubber  fabric  of  the  envelope.  Some  idea  of  what  this  amount 
of  gas  means  may  be  gained  from  the  fact  that  its  equivalent  in  coal 
gas  fed  to  an  ordinary  five-foot  burner  would  supply  it  for  more 
than  ten  years  constant  burning.  The  lower  part  of  the  illustration 
shows  a  true  plan  view  of  the  gas-generating  plant,  while  the  upper 
part  is  a  somewhat  distorted  section,  drawn  in  this  manner  to  more 
clearly  illustrate  the  passage  of  the  gas  in  the  course  of  its  generation 
and  purification.  The  cost  of  this  plant,  plus  that  of  the  material 
necessary  to  inflate  the  Akron  but  once,  would  be  sufficient  to  pay 
for  several  modern  aeroplanes. 


81 


82  DIRIGIBLE   BALLOONS 

ACHIEVEMENTS  OF  THE  DIRIGIBLE 

The  year  1910  will  go  down  in  history,  not  alone  as  marking 
the  first  actual  transportation  of  passengers  through  the  air  for  hire, 
but  likewise  the  first  attempts  to  cross  the  Atlantic  in  an  airship. 
Two  of  these  attempts  were  proposed  and  one  was  actually  under- 
taken. This  was  the  ill-fated  cruise  of  the  America,  already  described, 
but  the  failure  of  its  promoters  to  achieve  their  object  has  proven  no 
deterrent  to  others  intent  upon  accomplishing  the  same  feat.  In 
fact,  1910  may  be  said  to  mark  the  beginning  of  an  era  of  aerial  trans- 
portation, as  while  the  wreck  of  the  Zeppelin  after  having  made 
but  comparatively  few  trips,  put  a  sudden  end  to  the  much  adver- 
tised "regular  passenger  service"  for  the  time  being,  neither  this 
nor  the  subsequent  wrecking  of  other  Zeppelin  airships  proved 
sufficient  to  discourage  the  promoters.  During  1911,  the  Zeppelin 
and  several  other  German  companies  formed  for  the  purpose  carried 
hundreds  of  passengers,  and  it  is  a  fact  worthy  of  note  that  since  the 
latter  part  of  that  year,  one  of  the  large  steamship  companies  has 
combined  announcements  of  aerial  trips  with  those  of  the  sailing  of 
its  steamers;  and  tickets  good  for  flights  in  Germany  can  be  bought 
in  this  country.  The  success  of  the  German  dirigible  passenger 
service  has  been  such  that,  in  spite  of  the  numerous  disasters  which 
have  fortunately  been  free  from  fatalities,  a  similar  service  is  to  be 
instituted  in  this  country,  using  German  airships  at  first. 

Wellman's  Expedition.  Owing  to  its  novelty,  as  well  as  its 
daring,  the  attempt  of  Wellman  to  cross  the  Atlantic  in  the  America, 
is  worthy  of  record,  particularly  as  his  failure  has  not  deterred  others 
from  attempting  the  same  feat,  and  doubtless  it  will  not  be  very 
long  before  it  is  actually  accomplished.  What  such  an  accomplish- 
ment will  show,  however,  apart  from  the  fact  that  the  aeronauts 
met  unusually  favorable  conditions,  is  questionable.  In  order  that 
the  appended  account  may  be  free  from  the  sensational  coloring 
given  the  America's  trip  by  the  newspaper  and  magazine  reports, 
excerpts  are  taken  from  the  story  of  Vaniman,  the  chief  engineer, 
though  it  is  to  be  noted  that  his  version  exhibits  some  irreconcilable 
differences  with  that  of  Wellman  himself. 

The  start  was  made  at  8  A.M.,  October  15,  1910,  from  Atlantic 
City  in  a  light  southwesterly  breeze,  there  being  considerable  fog. 


82 


DIRIGIBLE   BALLOONS  S3 

The  attempt  was  really  premature  and  probably  would  not  have 
been  made  at  that  time,  had  it  not  been  for  the  question  of  good 
faith  on  the  part  of  Wellman  raised  by  the  press.  So  many  delays 
had  been  experienced  that  the  date  of  starting  had  been  constantly 
postponed  from  month  to  month  and  Wellman  was  accused  by 
inference,  if  not  openly,  that  he  had  no  intention  whatever  of  ever 
making  the  attempt.  The  actual  start  was  accordingly  made  under 
unfavorable  conditions  and  without  any  previous  trials  of  the  air- 
ship that  would  doubtless  have  revealed  the  defects  later  brought 
to  light  when  there  was  no  possibility  of  remedying  them.  Every- 
thing had  apparently  been  in  a  state  of  readiness  for  weeks  prior  to  the 
start,  but  this  was  not  actually  the  case,  and  while  numerous  indoor 
tests  of  the  machinery  had  been  made  this  was  not  the  equivalent 
of  actual  trials  in  the  open.  The  "after"  engine,  as  already  explained, 
was  arranged  to  drive  its  two  propellers  through  the  medium  of  bevel 
gearing  so  that  the  propeller  shafts,  which  were  at  right  angles  to 
the  extended  shafts  coupled  to  the  engine,  could  be  swung  bodily 
about  in  a  complete  circle,  thus  making  it  possible  to  employ  their 
thrust  in  any  direction  desired,  but  more  particularly  in  a  vertical 
line  so  as  to  force  the  balloon  up  or  down.  The  fatal  mistake  con- 
sisted in  not  supplying  this  engine  with  a  flywheel.  For  four  hours 
it  operated  steadily,  not  missing  more  than  two  explosions  in  this 
entire  period,  but  the  absence  of  the  flywheel  (for  which  it  had  been 
designed  and  the  loss  of  which  was  not  compensated  for  by  the  pro- 
pellers) produced  la  pounding  action,  and  the  keys  of  the  bevel 
gearing  worked  loose,  rendering  the  engine  useless.  How  serious 
this  loss  was  could  not  be  appreciated  until  the  next  day,  as  will 
presently  be  explained. 

During  Saturday  evening  the  airship  was  in  danger  of  being 
blown  onto  the  shore  of  Long  Island  by  a  southerly  shift  of  the  wind, 
and  it  was  necessary  to  use  the  engine  to  keep  her  headed  off  shore. 
The  fog  still  persisted  and  it  was  feared  that  the  two-ton  equilibrator 
trailing  in  the  water  would  strike  some  vessel,  resulting  in  immediate 
disaster  to  the  airship,  as  it  would  draw  it  down  into  the  sea ;  further- 
more, it  might  do  a  great  deal  of  damage  to  the  vessel  encountered. 
The  moon  was  full  but  owing  to  the  fog  it  was  impossible  to  see  any- 
thing ahead.  Two  lookouts  were  stationed  to  endeavor  to  prevent 
collisions.  Suddenly  the  sound  of  a  fog  horn  was  heard,  and  almost 


83 


84  DIRIGIBLE   BALLOONS 

immediately  the  masthead  of  a  schooner  loomed  up  dead  ahead. 
But  the  airship  responded  beautifully  to  its  helm  and  swung  to  one 
side,  just  clearing  the  vessel  by  a  narrow  margin.  This  experience 
as  recounted  later  by  the  captain  of  the  vessel  was  most  thrilling. 
He  had  no  knowledge  of  any  contemplated  voyage  across  the  ocean 
by  airships,  and  he  was  greatly  frightened  when  the  monster  loomed 
up  out  of  the  fog  with  the  sparks  streaming  from  its  red-hot  exhaust 
pipes  and  making  a  terrific  racket  with  its  unmuffled  engine.  The 
lashing  equilibrator  with  one  tank  empty,  owing  to  leakage  of  gaso- 
line, was  being  pounded  by  the  water,  giving  a  weird,  hollow  sound 
that  added  greatly  to  the  terror  of  the  crew.  This  was  the  only 
approach  to  a  collision  experienced. 

Vaniman  had  no  idea  that  the  engine  was  throwing  sparks 
until  this  was  revealed  by  the  darkness.  The  exhaust  pipe  terminated 
directly  back  of  the  propellers,  so  that  the  sparks  were  carried  off 
in  the  wake  of  the  latter  and  there  was  little  likelihood  of  their  lodging 
in  the  fabric  of  the  balloon.  The  airship  had  been  traveling  through 
fog  ever  since  morning  and  was  dripping  wet,  so  there  was  no  danger 
of  fire.  Sunday  morning,  the  fog  still  continued  and  the  wind, 
veering  to  the  west,  began  to  freshen,  making  it  unnecessary  to  use 
the  engine.  But  with  the  freshening  of  the  wind  a  new  danger  arose. 
The  airship  had  started  out  from  Atlantic  City  with  an  extra  supply 
of  gasoline  aboard,  so  that  it  hung  very  low  over  the  water,  all  but 
six  tanks  of  the  thirty  in  the  equilibrator  being  submerged.  With 
the  freshening  wind,  it  was  found  necessary  to  throw  over  gasoline 
in  order  to  lighten  the  airship.  Had  this  gasoline  been  left  behind 
to  start  with,  the  airship  would  have  made  much  better  progress 
and  would  have  been  much  farther  along  when  the  wind  freshened, 
but  the  extra  fuel  was  taken  on  with  the  expectation  that  the  fog 
would  eventually  lift,  and  under  the  heat  of  the  sun  the  gas  in  the 
balloon  would  expand  and  lift  the  balloon  to  its  normal  position. 
However,  the  sun  remained  hidden  by  banks  of  fog. 

Sunday  afternoon,  the  wind  assumed  a  velocity  of  35  miles  an 
hour.  The  night  grew  very  cold,  shrinking  the  balloon  and  making 
it  necessary  to  throw  out  more  gasoline.  Then  a  peculiar  motion 
began  to  manifest  itself.  It  will  be  recalled  that  the  purpose  of  the 
equilibrator  was  to  hold  the  airship  at  a  practically  constant  level 
above  the  sea;  in  other  words,  the  airship  and  the  sea  were  to  divide 


84 


DIRIGIBLE   BALLOONS  85 

between  them  the  burden  of  supporting  the  two-ton  equilibrator. 
If  the  ship  showed  a  tendency  to  rise,  it  would  be  weighted  down  by 
having  to  lift  a  greater  weight  off  the  sea,  and  if  it  showed  a  tendency 
to  descend,  it  would  be  lightened  by  letting  more  of  the  equilibrator 
float,  with  the  result  that  the  airship  should  be  held  at  a  practically 
uniform  elevation  above  the  water.  However,  when  the  wind 
freshened,  the  drag  of  the  equilibrator  began  to  set  up  a  surging 
motion.  It  would  pull  the  airship  down,  slowly  but  surely,  until  it 
almost  touched  the  water,  then  the  airship  would  rebound  with 
gathering  momentum,  pulling  the  equilibrator  out  of  the  water,  tank 
by  tank,  until  it  was  lifted  entirely  clear  of  the  surface.  The  equili- 
brator would  then  swing  forward  like  a  huge  pendulum  and,  as  its 
weight  overcame  the  buoyancy  of  the  balloon,  it  would  strike  the 
water,  and  the  dragging  action  would  recommence.  In  this  way, 
the  airship  kept  constantly  oscillating  up  and  down,  the  period  of 
the  oscillations  being  about  ten  minutes.  On  one  occasion  the  big 
balloon  swung  so  near  the  water  that  the  waves  struck  the  lifeboat 
cradled  below  it.  There  seemed  to  be  no  way  of  preventing  this. 
It  was  then  that  Vaniman  realized  the  loss  of  his  after  motor, 
for  had  he  been  able  to  use  these  propellers  to  lift  the  airship  when  it 
showed  a  tendency  to  be  dragged  down,  the  oscillation  could  have 
been  largely,  if  not  entirely,  prevented. 

The  thrust  of  the  propellers  which  might  thus  have  been  used 
was  800  pounds,  and  this  would  have  been  more  than  sufficient  to 
correct  the  surging  movement.  Had  the  airship  been  further  lightened, 
it  might  have  been  able  to  lift  the  equilibrator  clear  of  the  water 
when  there  would  have  been  no  drag  to  contend  with  and  it  would 
have  been  possible  to  steer  the  craft  into  the  wind.  As  it  was,  the 
airship  was  helpless.  It  was  drifting  broadside  to  the  wind.  As 
long  as  the  oscillatory  motion  kept  up,  it  would  have  been  dangerous 
to  have  headed  the  vessel  into  the  wind,  for  then  it  would  have  pitched 
badly,  tending  to  stand  straight  up  and  down.  As  long  as  the  wind 
held  from  the  right  quarter,  it  mattered  little  whether  the  engine 
was  used  or  not,  but  the  oscillations  were  nerve  racking,  and  not  at 
all  calculated  to  inspire  the  crew  with  any  feeling  of  security.  The 
pounding  of  the  waves  on  the  equilibrator,  about  which  so  much 
was  published,  amounted  to  practically  nothing,  according  to 
Vaniman.  The  jars  were  not  at  all  serious,  but  considering  the 


85 


86  DIRIGIBLE   BALLOONS 

experiences  they  had  gone  through,  the  members  of  the  crew  were 
ready  to  exaggerate  the  slightest  unusual  shock,  and  the  harmless 
pounding  appeared  to  assume  dangerous  proportions. 

Sunday  was  a  night  of  grave  apprehension.  It  was  found  neces- 
sary to  throw  over  a  quantity  of  the  precious  gasoline,  as  well  as  the 
damaged  engine  (a  90-horse-power  automobile  motor)  in  an  effort 
to  prevent  the  airship  from  being  dragged  down  into  the  water. 
Monday,  however,  the  sun  rose  clear  and  hot  and  beat  upon  the  gas 
bag.  There  was  no  wind  to  counteract  the  heating  effect,  because 
the  vessel  was  drifting  with  the  wrind,  and  the  gas  heated  rapidly  and 
expanded  so  quickly  that  it  lifted  the  balloon  and  its  heavy  equili- 
brator  to  an  altitude  of  3,000  feet  before  it  could  be  checked.  The 
rise  was  so  rapid  as  to  make  the  crew  dizzy  and  affect  their  ear  drums. 
Vaniman  opened  the  valves  to  let  out  the  hydrogen,  meanwhile 
closely  watching  the  statoscope  for  the  first  signs  of  descent.  Despite 
the  utmost  precautions  and  the  careful  handling  of  the  valves,  the 
descent  took  place  quite  as  suddenly  as  the  ascent.  As  the  balloon 
fell  it  gathered  momentum  and  also  lost  buoyancy,  due  to  the  con- 
traction of  the  gas  bag  in  the  increasing  density  of  the  lower  strata 
of  air.  This  contraction  of  the  gas  bag  produced  a  constant  down- 
ward accelerating  force,  greatly  increasing  the  speed  of  the  descent. 
However,  the  equilibrator  served  as  a  cushion  to  ease  the  fall.  It 
entered  the  water  at  high  speed  and  sank  until  the  last  can  was  sub- 
merged before  the  airship,  relieved  of  its  weight,  could  recover  and 
rise  again.  This  one  experience  was  sufficient  to  show  the  value  of 
the  equilibrator. 

Had  there  been  no  device  of  this  nature  provided,  the  airship 
must,  inevitably,  have  been  carried  into  the  sea  at  the  end  of  its 
downward  plunge,  striking  the  water  at  such  a  velocity  as  to  have 
crushed  out  the  lives  of  all  on  board.  Had  the  airship  started  without 
an  equilibrator,  it  would  frequently  have  been  necessary  to  throw 
over  ballast  to  prevent  such  descents,  and  it  would  as  frequently 
have  been  necessary  to  open  the  gas  valves  to  prevent  ascension  to 
dangerously  high  altitudes.  It  was  Vaniman's  opinion  that 
without  the  equilibrator  the  airship  could  not  have  kept  afloat  a 
single  day.  As  it  was,  this  single  ascent  cost  fully  one-seventeenth 
of  the  total  supply  of  gas. 

Monday,  the  third  day  out,  the  sailing  was  good;  but  the  wind 


86 


DIRIGIBLE   BALLOONS  87 

had  veered  around  to  such  a  direction  as  to  drive  the  airship  south- 
ward. It  was  then  planned  to  head  for  the  Azores  Islands,  and  later  in 
the  day  a  still  further  shift  of  the  wind  made  it  necessary  to  head  for 
Bermuda.  The  oscillatory  motion  continued  under  the  action  of  the 
wind  and  it  was  necessary  to  lighten  the  balloon  of  still  more  gasoline. 

When,  early  in  the  morning  of  Tuesday,  the  lights  of  the  Trent 
were  made  out,  it  was  decided  that  it  would  be  foolish  to  continue 
the  voyage  farther.  There  remained  but  little  gasoline  in  the  main 
tank  and  much  of  the  gas  in  the  balloon  had  been  wasted.  There 
was  every  probability  that  the  airship  could  keep  afloat  during  the 
day,  but  the  chances  of  staying  in  the  air  at  night,  when  the  reduced 
gas  supply  in  the  envelope  would  be  condensed  by  the  cold,  were 
rather  slim.  Furthermore,  there  was  the  difficulty  of  launching  the 
lifeboat  with  the  heavy  equilibrator  trailing  in  its  wake,  and  it  seemed 
far  more  prudent  to  undertake  to  launch  the  boat  while  a  vessel  stood 
by  ready  to  give  assistance. 

The  problem  of  launching  the  boat  was  no  small  one.  The  airship 
was  drifting  at  the  rate  of  15  knots,  broadside  to  the  wind,  as  may  be 
seen  by  noting  the  angle  which  the  white  trail  of  the  equilibrator 
makes  with  the  shadow  of  the  gas  bag  in  the  illustration,  Fig.  31,  taken 
from  the  deck  of  the  Trent.  This  meant  that  the  boat,  which  could 
not  be  swung  athwart  the  car,  would  have  to  be  launched  sideways. 
The  valves  were  opened  until  the  boat  dropped  to  within  4  feet  of  the 
water.  All  the  materials  that  were  saved  from  the  airship  were  stowed 
in  the  bottom  of  the  lifeboat  to  act  as  ballast.  At  a  given  signal,  the 
automatic  shackles  which  held  the  boat  to  the  airship  were  released 
and  the  boat  dropped  into  the  sea.  Despite  the  fact  that  it  was 
traveling  broadside  at  a  rate  of  15  knots,  it  did  not  ship  a  gallon  of 
water.  As  soon  as  the  balloon  was  released  of  this  weight,  it  shot  up 
into  the  air  and  the  equilibrator  was  whipped  out  of  the  water, 
striking  the  boat  and  crushing  the  forward  air  compartment,  for- 
tunately above  the  water  line.  Before  cutting  loose  from  the  airship, 
Vaniman  tied  a  can  to  the  gas  valve  of  the  balloon  so  that  the 
latter  would  lose  its  gas,  thus  obviating  any  danger  of  its  rising  out 
of  the  sea  and  acting  as  a  menace  to  the  rigging  of  vessels  at  sea  or 
buildings  along  the  coast.  When  last  seen,  the  balloon  was  settling, 
nose  down,  into  the  water. 

Thus  ended  one  of  the  most  remarkable  voyages  ever  under- 


87 


88 


DIRIGIBLE  BALLOONS 


taken,  and  certainly  the  most  remarkable  rescue  at  sea.  The  results 
accomplished  were  two  records  for  dirigibles :  One  of  duration  which 
consisted  of  71 J  hours  in  the  air,  as  against  36  hours,  which  was 
made  by  Zeppelin;  and  the  other  of  distance,  which  was  put  at  1,008 
miles  by  navigator  Simon  in  his  logbook,  the  previous  distance  record 
having  been  made  by  Zeppelin  when  he  covered  800  miles  without 
coming  to  earth.  However,  the  object  of  the  expedition-  \vas 
not  to  establish  records.  The  underlying  idea  of  Wellman  and 


Fig.  31.     View  of  the  "America"  Settling  into  the  Sea  Prior  to  the  Release 
of  the  Lifeboat.     Picture  Taken  from  the  Deck  of  the  S.  S.  Trent 

Vaniman  has  been  to  stimulate  interest  in  dirigible  balloons,  to 
study  their  behavior  under  varying  conditions,  and  to  promote  their 
development.  It  is  a  tribute  to  the  skill  of  the  engineer  who  designed 
the  America  that  on  its  first  voyage,  without  any  preliminary  trial, 
it  broke  all  previous  records,  and,  as  far  as  the  machinery  is  con- 
cerned, with  the  exception  of  the  one  defective  engine,  maintained 


DIRIGIBLE   BALLOONS  89 

every  part  intact.  Not  a  stay  was  broken  and  not  a  nut  needed 
tightening  during  the  voyage. 

Brucker's  Proposed  Expedition.  Wellman's  contemporary,  who 
intended  to  attempt  a  transatlantic  voyage  by  dirigible  in  1910,  is 
Joseph  Brucker,  a  German-American,  whose  project  antedates 
Wellman's  attempt.  Owing  to  delays  in  getting  ready,  it  was  impos- 
sible to  start  before  too  late  in  the  season — now  it  is  proposed  to 
carry  out  the  expedition  early  in  the  Spring  of  1912,  but  along  some- 
what different  lines.  Before  describing  Brucker's  apparatus,  a  brief 
resume  of  his  comments  on  the  reasons  for  Wellman's  failure  will  be 
of  interest.  He  says,  quoting  from  UmscJiau,  Berlin: 

I  have  repeatedly  pointed  out  that  in  the  present  state  of  the  art  it  will 
be  impossible  to  cross  the  Atlantic  in  an  airship  north  of  the  35th  parallel  of 
latitude,  because  in  that  region  one  depression  follows  another,  and  particu- 
larly in  the  fall.  Wellman  was  meteorologically  ill-advised.  At  the  time  of 
his  start,  it  was  well  known  that  a  violent  hurricane  was  raging  in  Cuba,  and 
that  such  violent  disturbances  of  the  atmosphere  in  those  latitudes  are  fol- 
lowed by  extraordinary  collateral  phenomena  in  latitudes  35  to  40  degrees 
north.  Wellman's  chart  of  the  journey  confirms  this. 

It  also  seems  that  Wellman  could  not  rely  on  his  motors — one  was  dis- 
abled soon  after  he  set  out  and  the  other  was  probably  not  powerful  enough 
to  enable  the  America  to  keep  a  more  easterly  course.  The  America  seems  to 
have  traveled  more  like  a  free  balloon,  for  which  reason  this  performance 
should  not  be  regarded  as  a  record  for  dirigibles.  Wellman  would  in  all  prob- 
ability hardly  maintain  that  he  could  follow  a  definite  course.  Another  fatal 
error  was  the  equilibrator,  to  which  Engineer  Vaniman  pinned  his  faith.  This 
was  in  itself  a  very  cumbrous  contrivance  with  its  thirty  gasoline  tanks  and 
turned  out  to  be  a  source  of  danger. 

Dr.  Alt,  of  the  Munich  Meteorological  Station,  and  I  have  made  many 
experiments  during  the  last  few  months  with  arrangements  similar  to  Well- 
man's equilibrator.  We  have  given  the  tanks  most  diverse  forms,  only  to  come 
to  the  conclusion  that  all  such  devices,  when  an  airship  is  traveling  over  water, 
not  only  produce  enormous  resistance,  but  are  highly  dangerous  to  the  airship 
itself.  The  America  seems  to  have  perished  from  appendicitis.  A  surgical 
operation,  however,  could  not  be  performed,  because  the  airship,  if  it  had  been 
relieved  of  this  burden,  wrould  have  risen  to  an  enormous  height  and  would 
have  faced  new  dangers. 

The  expedition  which  I  have  organized  is  the  result  of  scientific  study. 
It  is  our  intention  to  start  from  the  Cape  Verde  Islands,  about  2,350  miles 
from  the  Lesser  Antilles.  There  are  no  counter  winds  in  our  course,  no  fogs, 
no  storms,  and,  therefore,  it  should  be  possible  to  travel  with  the  wind  at  a  rate 
of  about  7  meters  (23  feet)  per  second  or  15  miles  an  hour. 

Brucker's  selection  of  a  route  founded  on  taking  advantage  of 
a  prevailing  trade  wind  is  not  new.  Edgar  Allan  Poe  suggested  the 
plan  of  sending  a  balloon  drifting  with  the  trade  winds  from  Africa 


90  DIRIGIBLE   BALLOONS 

to  America,  in  one  of  his  realistic  novels.  In  France,  it  had  been 
seriously  proposed  even  prior  to  this,  and  it  was  again  taken  up  in 
the  late  nineties  when  Santos-Dumont  was  keeping  interest  in 
aeronautics  alive  in  Europe  by  his  experiments.  Strange  as  it  may 
appear,  the  first  development  of  the  dirigible  caused  these  projects 
to  be  forgotten,  for,  with  its  aid,  the  primary  idea  was  that  the  wind 
was  to  be  overcome  and  not  taken  advantage  of  as  in  the  spherical 
balloon.  The  chief  remedy  sought  was  increased  speed,  while  Zeppe- 
lin's sole  idea  was  to  increase  the  radius  of  action  in  order  that  an 
airship  might  be  capable  of  outlasting  a  storm. 

To  finance  his  project,  Brucker  incorporated  the  Transatlantische 
Plug  Expedition,  with  a  board  of  directors  comprising  some  of  the 
foremost  scientific  and  commercial  leaders  of  Germany.  The  stock 
has  been  subscribed  by  a  number  of  individuals,  though  the  Swiss 
chocolate  manufacturing  firm  "Suchard"  has  guaranteed  to  meet 
most  of  the  expense,  hence,  the  name. 

Type  of  Balloon.  The  balloon  is  of  the  type  of  the  Parseval  VI, 
but  modified.  It  measures  about  240  feet  in  length  by  68  feet  maxi- 
mum diameter,  which  is  at  the  first  third  of  its  total  length,  as  in  the 
Parseval.  The  bow  is  spheroid,  or  egg-shaped,  while  the  stern  is 
sharply  pointed.  The  envelope  has  a  capacity  of  9,400  cubic  meters 
(more  than  330,000  cubic  feet),  the  balloonet  representing  more  than 
a  third  of  this,  or  3,500  cubic  meters,  which  is  equal  to  the  total 
displacement  of  a  typical  French  airship.  This  insures  a  rigid  hull, 
even  after  an  extensive  loss  of  gas,  enabling  the  ship  to  meet  the 
most  extreme  conditions  that  are  a'pt  to  rise  in  a  long  voyage.  Efforts 
have  been  made  to  give  not  only  a  tremendous  radius  of  action, 
but  also  the  highest  attainable  degree  of  safety.  Both  of  these 
requirements  have  been  realized  by  building  a  ship  of  ample  size 
designed  for  low  speed.  The  weight  thus  saved  is  utilized  to  make 
a  thoroughly  strong  structure  and  in  equipping  the  vessel  with  safety 
appliances.  In  fact,  the  craft  represents  the  very  latest  product  of 
the  German  aerial  dockyards. 

The  envelope  is  made  of  a  special  fabric  consisting  of  three 
layers  of  cloth,  two  of  rubber,  and  a  light  rubber  coating  on  both 
surfaces.  This,  together  with  the  large  volume,  and  the  ratio  of 
four  to  one  between  length  and  diameter,  resulting  in  a  comparatively 
small  surface  per  unit  volume,  should  give  excellent  gas-retaining 


90 


DIRIGIBLE   BALLOONS  91 

qualities.  Even  the  Zeppelin  VI,  which  was  burned  at  Baden-Baden, 
retained  its  gas  for  many  weeks  at  a  time,  although  in  daily  service. 
In  the  Suchard,  gas  loss  by  diffusion  will  be  negligible  as  compared 
with  the  amount  escaping  when  the  safety  valves  are  opened  under 
the  tropical  sun.  This  loss  is  to  be  minimized  by  a  special  patented 
device,  which  is  perhaps  the  most  important  feature  of  the  design 
of  the  entire  apparatus. 

Novel  Features.  Advantage  has  been  taken  of  the  fact  that 
the  route  will  be  entirely  over  water.  The  plan  is  to  scoop  ballast 
from  the  ocean  whenever  needed  by  means  of  buckets  on  a  steel 
cable.  These  buckets  are  of  sheet  steel  of  a  shape  to  give  the  minimum 
resistance  when  filling.  Each  holds  seven  to  eight  gallons  and  has 
four  holes  in  front  to  permit  the  water  to  enter,  filling  quickly  and 
automatically  by  reason  of  the  motion  of  the  airship.  Although 
they  can  be  dropped  into  the  water  so  that  their  action  takes  place 
immediately,  the  effect  of  the  sun's  rays  is  also  very  sudden,  and 
dependence  is  not  placed  on  this  device  alone.  It  is  supplemented 
by  a  movable  weight,  the  position  of  which  regulates  the  inclination 
of  the  keel.  With  the  aid  of  this  arrangement,  a  certain  amount  of 
downward  force  can  be  called  into  play  by  aeroplane  action  through 
the  forward  movement  of  the  vessel.  It  practically  amounts  to 
changing  the  angle  of  incidence  as  is  done  in  an  aeroplane  with  the 
elevating  rudder. 

But  the  most  important  feature  is  an  original  device  for  cooling 
the  envelope  with  running  water.  Light  canvas  hose  extends  from 
the  boat  to  the  top  of  the  balloon,  where  it  encircles  the  gas  valve 
and  then  extends  back  along  the  balloon  in  both  directions.  It  is 
provided  with  a  number  of  perforations  along  its  sides,  ending  in  a 
hard-rubber  spray  nozzle  fore  and  aft.  From  a  tank  in  the  boat, 
water  is  pumped  through  the  hose,  flowing  in  a  thin  film  all  over  the 
envelope.  The  18-mile  breeze  caused  by  the  travel  of  the  airship 
will  cause  rapid  evaporation,  resulting  in  an  intense  cooling  effect. 
When  it  is  considered  that  the  airship  will  have  to  -undergo  the 
extreme  change  from  tropical  day  to  night  at  least  five  to  seven 
times,  it  will  be  evident  that  the  conditions  to  be  met  are 
extremely  more  dangerous  than  those  ordinarily  encountered 
on  land,  where  a  single  change  from  day  to  night  in  temperate 
zones  causes  most  serious  difficulties,  so  that  it  remains  to  be 


91 


92  DIRIGIBLE   BALLOONS 

seen  whether  the  results  obtained  with  these  safety  devices  will 
fulfill  expectations. 

Motive  Power.  Wellman's  plan  of  utilizing  a  car  and  a  lifeboat 
has  been  departed  from  by  combining  both  in  a  large  motor  boat. 
This  is  39  feet  long  by  12  feet  beam  and  7  feet  in  depth  and  is  equipped 
with  two  200-horse-power  motors,  which  will  not  only  drive  the  ship 
in  the  air,  but  the  boat  in  the  water,  in  case  of  abandonment.  It  is 
equipped  with  a  fire-  and  explosion-proof  gasoline  tank,  the  efficacy 
of  which  was  demonstrated  in  the  accident  to  the  Zeppelin  VI,  in 
which  the  tank  remained  intact  though  the  ship  was  burned.  The 
boat  provides  a  navigating  and  living  compartment,  a  complete 
machine  shop  for  making  repairs,  a  set  of  aeronautic  and  meteorologic 
instruments  and  a  large  store  of  provisions.  It  is  suspended  from 
the  envelope  in  the  same  manner  as  the  usual  car,  but  between  it 
and  the  envelope  a  light  passageway  is  suspended,  reached  from  the 
boat  by  a  rope  ladder.  It  gives  direct  access  to  the  envelope  and 
the  valves  and  also  provides  additional  "deck  space."  The  whole 
equipment,  however,  is  centered  in  the  boat  and  nothing  has  to  be 
transferred  in  an  emergency  as  in  the  America. 

It  is  hoped  that  the  Suchard,  with  its  speed  of  18  miles  an  hour, 
plus  the  steady  trade  wind  blowing  16  miles,  will  make  34  miles 
an  hour,  covering  the  distance  in  five  days,  if  the  machinery  holds 
out.  In  case  of  breakdown,  it  will  take  longer,  but  the  trade  winds 
will  insure  steady  progress,  while  there  seem  to  be  no  risks  that  could 
be  compared  in  the  least  with  those  that  Wellman  faced.  A  number 
of  trial  trips  will  be  made  before  embarking  on  the  actual  enterprise 
with  the  trade  wind,  which  allows  of  no  return.  In  the  light  of 
Wellman's  experience,  Brucker's  success  would  seem  to  depend  upon 
his  skill  in  handling  the  water-scooping  and  -spraying  apparatus, 
i.  e.,  his  ability  in  preventing  the  airship  from  rising  unduly.  If  he 
succeeds  in  avoiding  gas  losses  from  this  cause,  he  can  hardly  fail 
to  reach  the  West  Indies,  even  though  the  motors  give  out.  But 
even  a  few  minutes  failure  of  these  devices  would  suffice  to  send  the 
ship  to  the  clouds,  blowing  off  large  quantities  of  gas  and  spoiling 
all  chances  of  a  long  voyage.  The  air  balloonet  is  so  large  that  it 
should  compensate  for  considerable  expansion  or  contraction  of 
the  gas. 

Carrying  Passengers  by  Airship.     Deutschland.     For  a  time,  it 


DIRIGIBLE   BALLOONS  93 

seemed  as  if  the  year  1910  would  go  down  in  history  as  marking  the 
actual  inception  of  aerial  transportation  according  to  a  regular 
schedule.  The  Deutschland  (Zeppelin  VII)  was  a  true  ship  of  the 
air  and  on  a  most  elaborate  scale.  She  was  built  for  the  Deutsche 
Motorluftschiffahrt  Gesellschaft  (German  Aerial  Transportation  Com- 
pany), incorporated  to  do  an  aerial  passenger-carrying  business. 
The  airship  was  490  feet  long  and  had  a  capacity  of  27,400  cubic 
yards.  The  budget  of  this  aerial  packet  boat  was  as  follows:  The 
cost  of  the  airship  was  to  be  $150,000,  the  gas  bags  to  be  half  re-inflated 
every  week,  involving  a  monthly  consumption  of  390,000  cubic 
yards  of  hydrogen,  representing  an  annual  expenditure  of  $9,000; 
for  a  service  of  six  months  for  fuel  and  lubricants  $9,000  more  was 
allowed;  the  crew  of  seven  men  were  to  receive  $7,500,  while  $5,000 
was  allowed  for  anchorage  rights;  administration  and  unforeseen 
expenditures,  $11,500,  and  a  sinking  fund  of  $75,000,  bringing  the 
total  to  $116,500,  exclusive  of  the  cost  of  the  ship  itself. 

The  passenger  cabin  of  the  Deutschland  was  built  on  an  alumi- 
num frame  and  lined  with  rosewood  and  mahogany,  inlaid  with 
mother-of-pearl,  the  walls  consisting  of  mahogany  veneer  in  several 
layers  glued  together,  with  a  thickness  of  J  inch.  The  floor  was  also 
a  mahogany  veneer  of  the  same  thickness,  carpeted,  while  the  ceiling 
was  only  J  inch  thick,  veueer  being  employed  throughout  to  save 
weight.  The  entire  cabin  was  35  feet  long  by  1\  feet  wide  and 
weighed  only  1,600  pounds.  It  was  divided  into  five  compartments, 
each  containing  four  iane  seats,  of  which  1  foot  only  was  screwed  to 
the  floor,  so  that  the  chair  could  be  swung  in  all  directions.  Beside 
these  five  5-foot  compartments,  there  was  an  entrance  vestibule  and 
a  lavatory.  The  window  openings  were  remarkably  wide  so  that  an 
unobstructed  view  could  be  obtained  in  every  direction.  No  glass 
was  used  in  them,  however,  although  in  the  first  compartment  a 
sliding  glass  window  had  been  provided  for  testing  purposes. 

Twenty-four  passengers,  among  them  an  American  woman, 
five  Germans,  and  three  Englishmen,  booked  passage  at  the  estab- 
lished rate  of  $50  a  trip,  for  the  first  voyage.  All  told,  there  were 
thirty-three  persons  on  board  the  Deutschland  on  her  first  trip. 
She  started  from  Friedrichshafen  at  3  A.  M.,  traveled  up  the  valley 
of  the  Rhine  as  far  as  Cologne  and  reached  Diisseldorf  at  3  p.  M., 
having  covered  300  miles  as  the  crow  flies.  Favored  by  the  wind  the 


93 


94  DIRIGIBLE   BALLOONS 

speed  is  said  to  have  reached  50  miles  an  hour  at  times,  the  distance 
from  Mannheim  to  Diisseldorf  (180  miles)  having  been  covered  in 
four  hours;  an  express  train  taking  six  hours,  on  a  rather  winding 
track.  The  next  day,  the  Deutschland  made  a  round  trip  from  Diissel- 
dorf to  Dortmund  and  back,  going  the  37  miles  out  in  one  hour,  but 
taking  three  and  one-half  hours  for  the  return.  As  a  result,  voyages 
at  frequent  intervals  were  announced. 

On  June  29,  1910,  the  Deutschland  left  Dusseldorf  with  seven- 
teen passengers — all  newspaper  men — the  voyage  to  last  four  hours, 
but  the  ship  was  still  struggling  against  a  strong  head  wind  five  and 
a  half  hours  after  the  start  at  8:30  A.  M.  Then  the  motors  began  to 
give  trouble  and  the  fuel  threatened  to  run  short.  The  wind  had 
risen  to  a  storm  and,  without  the  aid  of  its  motors,  the  ship  shot  up 
to  a  height  of  5,000  feet,  then  dropped  as  suddenly  in  the  forest  of 
Teutoburg,  a  huge  tree  trunk  coming  up  through  the  floor  of  the 
cabin  to  the  dismay  of  the  passengers.  However,  it  broke  the  fall 
and  prevented  a  far  worse  disaster,  supporting  the  great  dirigible 
about  40  feet  from  the  ground.  The  entire  after  part  of  the  ship 
was  wrecked,  the  governing  planes  (horizontal  rudders)  being  broken 
and  the  gas  bag  being  torn  in  many  places.  A  company  of  infantry 
dismantled  the  wreck,  dissecting  the  aluminum  frame,  piece  by  piece, 
packing  the  motors  and  parts  of  the  car  and  rolling  up  the  fabric  of 
the  envelope,  so  that,  in  a  few  hours,  the  airship  was  on  its  way  back 
to  Friedrichshafen  on  the  railroad  instead  of  in  the  air.  Lieutenant 
Wagner,  commanding  the  Deutschland,  attributed  the  accident  to  a 
combination  of  adverse  circumstances  and  not  to  any  fault  of  the 
system.  The  chief  cause  was  the  sudden  downward  whirlwind,  but 
if  the  fuel  had  held  out,  the  gale  might  have  been  weathered.  As  it 
was,  she  was  at  the  mercy  of  the  wind.  In  rising  so  high,  a  great 
deal  of  gas  was  lost  and  the  wetting  of  the  envelope  in  the  rain  caused 
a  dangerous  loss  of  buoyancy. 

Zeppelin  VI.  A  little  less  than  two  months  later,  the  Zeppelin 
VI  was  also  destroyed.  On  September  14,  owing  to  a  breakdown 
of  one  of  the  motors,  the  envelope  caught  fire  while  the  crew  was 
cleaning  the  machinery  with  gasoline  from  an  open  tank.  The 
hydrogen  in  the  seventeen  compartments  instantly  ignited  and  the 
ship  was  completely  consumed  in  a  short  time.  During  the  fortnight 
preceding  the  fire,  the  Zeppelin  VI  had  covered  2,000  miles  and  had 


94 


DIRIGIBLE   BALLOONS  95 

carried  more  than  300  passengers.  She  was  the  speediest  Zeppelin 
ever  built,  being  credited  with  a  speed  of  38  miles  an  hour.  On 
August  28,  for  the  third  time  in  eight  days,  she  carried  thirty  pas- 
sengers from  Strasburg  to  Baden-Baden  and  back  in  three  hours. 

Miscellaneous  Exploits.  Earlier  in  the  year,  the  Zeppelin  II 
— one  of  the  German  military  fleet — was  also  destroyed  by  a  storm. 
While  journeying  from  Hamburg  to  Cologne,  it  was  necessary  to 
anchor  in  an  open  field.  On  April  25,  1910,  after  the  vessel  had  just 
received  a  new  charge  of  gas,  two  companies  of  soldiers  were  unable 
to  hold  it  down  in  a  high  wind  and  it  was  blown  away.  It  immediately 
rose  to  a  height  of  700  feet  and  sailed  away  with  the  wind;  twenty 
minutes  later  it  was  blown  to  the  ground  in  the  Lahn  Valley,  the  bow 
caught  in  the  telegraph  wires  and  then  the  wind  took  the  huge  gas 
bag  broadside  and  hurled  it  against  the  side  of  the  hill  at  Webers- 
burg,  completely  demolishing  it.  This  accident  affords  a  striking 
illustration  of  the  chief  shortcoming  of  the  dirigible — its  utter  help- 
lessness when  exposed  to  the  wind,  a  cause  that  led  to  the  loss  of 
La  Patrie  three  years  before,  when  the  company  of  soldiers  detailed 
for  that  service  were  unable  to  hold  the  ship  and  it  simply  blew  away, 
never  being  heard  of  again.  To  be  of  practical  use,  the  dirigible,  must 
be  large,  but  its  very  size  is  its  greatest  element  of  weakness,  as  the 
cost  of  erecting  numerous  sheds  to  accommodate  it  would  be  pro- 
hibitive, and  it  can  not  safely  anchor  in  the  open. 

In  addition  to  the  events  chronicled,  there  were  a  number  of 
successful  cross-channel  flights,  the  most  striking  being  the  round 
trip  of  the  Clement-Bayard  II  between  London  and  Paris,  which 
merely  afforded  an  excellent  example  of  what  may  be  done  under 
favorable  circumstances.  In  fact,  the  English  Channel  was  crossed 
not  less  than  three  times  in  a  month  by  airship,  one  of  the  trips  being 
made  in  an  English  dirigible,  by  E.  T.  Willows,  who  had  a  short  time 
prior  flown  from  Cardiff  to  London.  He  started  for  Paris  from  Lon- 
don, but  was  compelled  to  descend  50  miles  inland  from  Calais. 

Despite  the  number  of  huge  dirigibles  that  were  wrecked  in 
Germany  during  1910,  as  well  as  those  that  came  to  grief  in  England 
in  the  following  year,  a  great  impetus  has  been  given  their  building 
and  operation  for  passenger  service  in  the  former  country,  and 
numerous  inventors  are  devoting  attention  to  the  perfecting  of 
various  devices  to  aid  in  their  navigation.  The  pilot  'of  a  huge 


95 


96  DIRIGIBLE  BALLOONS 

dirigible  has  many  things  to  watch,  but  none  that  requires  closer 
attention  than  that  of  the  vertical  travel  of  the  ship,  to  keep 
track  of  which  the  barographs,  anemometers,  and  anemoscopes 
must  be  consulted  continually,  often  to  the  neglect  of  other 
duties,  which  gives  rise  to  dangerous  situations. 

Kodophone.  The  kodophone  is  an  instrument  specially  devised 
for  the  purpose  of  relieving  the  pilot  of  a  dirigible  of  the  nerve- 
racking  strain  of  watching  a  number  of  fine  instruments  to  detect 
whether  his  ship  is  rising  or  falling.  As  its  name  indicates,  it 
works  on  an  audible  rather  than  a  visual  principle.  The  device 
consists  of  a  wind  wheel  located  horizontally  in  a  cylindrical  metal 
casing  and  adapted  to  revolve  easily  on  a  vertical  shaft.  The  metal 
cylinder  is  in  turn  protected  by  a  heavy  wicker  basket.  The  wind 
wheel  is  accordingly  so  placed  that  only  a  vertical  current  of  air  will 
actuate  it.  A  slight  amount  of  vertical  play  is  allowed  the  wheel 
on  its  vertical  shaft,  so  that  if  the  wind  is  coming  from  below,  the 
wheel  will  rise  slightly  under  the  pressure  of  the  wind  turning  it  and 
will  operate  a  bell  above  it.  This  would  indicate  that  the  airship 
was  falling.  With  the  wind  coming  from  above,  the  process  would 
be  reversed  and  another  bell  of  a  different  tone  sounded.  Not  alone 
the  fact  that  the  airship  is  either  ascending  or  descending,  but  like- 
wise the  speed  and  the  entire  period  during  which  one  or  the  other 
takes  place,  are  directly  communicated  to  the  pilot  by  the  bells. 
When  both  are  silent,  he  knows  with  absolute  certainty  that  the 
airship  is  traveling  on  a  perfectly  horizontal  keel.  This  is  of  the 
greatest  importance  at  night,  when  the  necessarily  limited  amount 
of  light  on  the  instruments  makes  consulting  them  more  than  usually 
troublesome.  It  also  has  a  further  advantage  in  that  the  instruments 
merely  show  that  the  ship  has  fallen  or  has  risen  and  does  not  reveal 
whether  one  or  the  other  is  continuing,  except  by  close  observation. 
To  avoid  disturbance  due  to  horizontal  currents  being  deviated 
into  the  basket  by  the  propeller  or  similar  means,  the  metal 
cylinder  is  covered  at  the  top  and  bottom  by  fine  wire  gauze.  It 
will  be  at  once  apparent  that  the  pilot,  being  thus  continuously 
informed  by  the  bell  signal,  will  be  able  without  loss  of  time  to 
take  prompt  measures  for  correcting  any  unfavorable  action, 
saving  both  gas  and  ballast  and  increasing  the  range  of  the  ship. 

Another  instrument  that  the  aeronaut  finds  need  of  now  that 


96 


DIRIGIBLE   BALLOONS  97 

greater  altitudes  and  night  flights  have  become  more  common,  is 
one  that  will  enable  him  to  determine  his  position  readily.  Under 
the  circumstances,  indirect  methods  must  naturally  be  reverted  to 
and  several  such  methods  have  been  tried  in  the  past  few  years. 
Magnetic  measurements  have  been  employed  for  this  purpose  and 
successful  methods  of  informing  an  aeronaut  of  his  position  by 
wireless  telegraphy  have  been  devised.  Finally,  astronomical 
methods  have  been  proposed,  in  which  the  tedious  reduction  of  the 
observations  is  effected  by  special  apparatus.  This  method,  of 
course,  can  be  employed  only  at  night  in  clear  weather. 

Special  Aeronautical  Compass.  The  ordinary  compass  is  not 
of  great  value  to  the  aeronaut  or  the  aviator,  as  the  direction  of  travel 
must  be  figured  out  from  the  indication  of  the  compass  needle,  aided 
by  the  chart,  all  of  which  requires  concentration  that  it  is  difficult 
to  give  when  attention  is  required  by  so  many  other  things.  To 
overcome  this,  a  special  type  of  compass  has  been  invented  by  an 
American,  A.  G.  Marquis.  It  consists  of  a  needle  mounted  in  the 
usual  manner,  while  surrounding  it  in  the  same  horizontal  plane  is 
a  card  having  the  points  of  the  compass  marked  on  it.  This  chart 
is  reversed,  however,  as  to  north  and  south,  and  the  needle  is  so 
arranged  that  it  points  to  the  south  also.  The  result  is  that  the 
reflection  in  a  mirror  placed  at  an  angle  of  45  degrees  above  the  chart 
is  correct,  the  north  point  appearing  at  the  top  and  the  south  at  the 
bottom  of  the  mirror.  Instead  of  the  chart  moving  round  and  the 
needle  remaining  stationary  as  in  the  ordinary  compass,  the  needle 
itself  apparently  swings  with  each  alteration  in  the  course,  and 
continuously  indicates  the  direction  in  which  the  airship  or  aeroplane 
is  traveling.  The  apparent  movement  of  the  pointer  is  the  result 
of  an  optical  illusion,  for  the  needle  actually  remains  stationary  and 
the  chart  turns  in  the  usual  way.  With  a  liquid  of  comparatively 
heavy  specific  gravity  to  deaden  the  vibrations  of  the  needle,  this 
has  been  found  to  be  by  far  the  most  practical  and  ingenious  of  the 
many  special  types  of  compasses  that  have  been  advocated  for 
aeronautical  use.  One  of  the  best  methods  of  overcoming  vibration 
has  been  found  to  be  the  use  of  oil  for  floating  the  needle  and  a  bed 
of  springy  horsehair  for  holding  the  compass  case.  The  employ- 
ment of  a  compass  with  a  south-pointing  needle  dates  back  to  2600 
B.  c.  in  China,  where  it  was  used  for  land  "navigation." 


97 


THEORY  OF  AVIATION 

PART  I 
EARLY  DAYS  OF  AVIATION 

As  the  derivation  of  the  word  indicates,  aviation  is  employed 
•to  refer  solely  to  the  flying  machine,  or  the  heavier-than-air  type, 
while  under  the  general  term  aeronautics  are  included  balloons,  dir- 
igibles, and  similar  apparatus,  which  depend  upon  the  use  of  a  lighter- 
than-air  gas  to  give  them  the  necessary  lifting  power. 

Historical.  Cayley.  Man's  ideas  on  the  subject  of  flight  are 
so  old  as  to  be  legendary,  but  going  back  to  Icarus  or  before  him, 
would  not  be  of  even  academic  interest  in  the  present  connection. 
Like  that  of  the  dirigible,  the  actual  history  of  the  aeroplane  began 
about  a  century  ago,  and  just  as  Meusnier  conceived  the  dirigible 
complete,  embodying  in  his  first  designs  all  those  important  prin- 
ciples which  have  since  proved  to  be  indispensable,  so  did  Sir  George 
Cayley  achieve  a  startling  approach  in  his  pioneering  work  to  what 
present-day  success  has  shown  to  be  necessary  for  flight.  In  fact, 
Cayley's  machine  represents  the  true  prototype  of  the  modern  aero- 
plane, combining  features  of  both  the  Wright  and  Bleriot  forms  of 
construction.  It  had  a  single  long,  narrow  plane  of  the  proportions 
since  demonstrated/  to  be  the  most  effective  and  was  designed  to  be 
"drawn"  by  two  screws  run  by  chains  from  a  single  motor,  the  pro- 
pellers being  placed  forward  and  one  on  either  side,  while  stability, 
elevation,  and  steering  were  to  be  obtained  through  the  medium  of  a 
tail. 

More  remarkable  by  far,  however,  was  the  knowledge  of  true 
principles  displayed  by  its  inventor;  the  proper  calculation  of  the 
center  of  thrust  and  the  fact  that  displacement  takes  place  towards 
the  front  being  known  to  Cayley.  As  in  the  case  of  the  dirigible,  it 
required  almost  a  century  to  "rediscover"  these  principles  and  appre- 
ciate their  value  as  Cayley  described  his  machine  in  detail  in  Nichol- 
son's Journal  in  1809.  He  even  dwelt  on  the  subject  that  is  now 
engrossing  the  foremost  designers  and  inventors,  automatic  stability, 

Copyright,  1912,  by  American  School  of  Correspondence. 


99 


2  THEORY   OF   AVIATION 

and  described  a  means  of  obtaining  it.  Unlike  so  many  early  investi- 
gators, Cay  ley  did  not  end  with  planning  a  machine  but  actually 
built  it.  This  first  attempt  was  really  the  original  glider,  as  it  had 
no  motor.  The  results  obtained  with  it  were  so  promising  that  a 
second  machine  was  constructed  and  equipped  with  a  small  engine 
designed  to  be  run  by  a  tank  of  compressed  air,  and  the  form  given 
the  latter  shows  that  the  importance  of  wind  resistance  was  fully 
appreciated.  Unfortunately,  Cayley's  experiments  terminated  with 
the  smashing  of  his  machine  in  its  trials. 

Henson.  That  the  results  of  his  investigations  were  not  entirely 
lost,  however,  is  evident  from  Henson's  machine  of  1842,  which  was 
an  even  more  astonishing  anticipation  of  modern  invention.  Henson 
had  not  alone  grasped  the  general  principles  but  had  also  anticipated 
the  actual  construction  of  the  aeroplanes  that  are  performing  such 
wonders  in  the  air  today.  His  machine  was  a  monoplane  and  the 
wings  with  their  ribbing  and  silk  covering,  stayed  above  and  below 
to  central  posts  placed  in  the  main  body,  is  almost  identical  with 
that  of  the  French  monoplane,  the  auxiliary  trussing  at  the  center 
of  the  planes  constituting  an  arrangement  employed  on  the  Antoi- 
nette. In  addition  to  the  main  planes,  there  was  a  hinged  rear  tail, 
and  a  rudder  for  vertical  and  horizontal  control,  and  there  was  like- 
wise a  three-wheel  chassis  on  which  the  machine  was  designed  to  run 
when  on  the  ground.  As  a  parallel  to  the  Wright  starting  rail, 
Henson  proposed  to  employ  an  inclined  plane,  the  run-down  which 
would  give  the  initial  impulse  necessary  to  launch  the  machine  in 
the  air. 

The  main  planes  measured  30  by  150  feet,  giving  an  area  of 
4,500  square  fe£t,  designed  to  be  covered  with  silk  or  linen  and  to 
be  perfectly  rigid,  although  an  arrangement  of  cords  was  devised 
for  "reefing"  or  "setting"  the  coverings  of  the  wings  or  planes,  each 
of  the  latter  being  divided  into  three  independent  sections  for  this 
purpose.  The  tail  was  50  feet  long  and  this,  as  well  as  the  rudder, 
was  controlled  by  cords  from  the  car.  A  small,  vertical  plane  was 
placed  at  the  center  of  the  main  planes  to  check  lateral  oscillation. 
All  of  the  struts  and  braces  were  designed  to  present  the  minimum 
resistance  to  the  air. 

A  light  but  very  strong  car  was  built  directly  under  the  central 
portion  of  the  main  plane  and  housed  the  power  plant  which  consisted 


100 


THEORY   OF   AVIATION 

of  a  two-cylinder,  condensing  steam  engine,  and  water-tube  boiler. 
The  engine  was  capable  of  delivering  about  20  horse-power  and  was 
designed  to  drive  two  six-bladed  propellers,  20  feet  in  diameter. 
The  condenser  was  practically  the  automobile  radiator  of  many 
years  later,  a  series  of  small,  vertical  tubes  designed  to  be  cooled  by 
the  air,  so  that  only  20  gallons  of  water  were  necessary,  and  the  total 
weight  of  the  power  plant,  including  its  water  supply,  did  not  exceed 
600  pounds.  Every  part  of  the  machine  was  built  to  withstand 
stresses  of  a  nature  that  only  an  expert  engineer  could  foresee  would 
be  placed  upon  it.  That  Henson's  machine  would  undoubtedly 
have  met  the  fate  that  rewards  every  builder  of  an  ambitious 
structure  who  has  not  the  least  idea  of  how  to  fly  it,  is  a  foregone 
conclusion. 

Miscellaneous.  This  was  probably  responsible  for  the  return 
to  first  principles  that  took  place  about  16  years  later,  when  Le  Bris 
demonstrated  the  first  man-carrying  kite  in  1856.  To  obtain  the 
necessary  lifting  force,  the  kite  was  towed  by  a  wagon.  Wenham, 
in  1866,  made  the  first  experiments  in  soaring  or  gliding.  This  was 
with  a  triplane  and  constituted  the  forerunner  of  the  apparatus 
employed  by  Chanute,  Archdeacon,  and  the  Wrights  30  to  35  years 
later.  Several  years  prior  to  Wenham's  experiments,  Nadar,  D'Ame- 
court,  and  De  la  Handelle  carried  out  an  extended  series  of  investi- 
gations, D'Amecourt  building  a  working  model  of  a  steam  helicopter 
—the  first  of  its  kind — in  1862.  Enrico  built  another  steam  heli- 
copter in  1878, 'weighing  all  told  6f  pounds,  which  actually  sustained 
itself  in  the  air  for  a  short  time,  while  a  year  later  Penaud  con- 
structed model  aeroplanes  on  the  lines  of  the  present-day  monoplane 
that  actually  soared,  and  Tatin's  compressed-air  machine  suspended 
by  a  cord  from  a  circular  track  showed  its  ability  to  fly  independ- 
ently of  its  support. 

Langley.  What  may  be  regarded  as  the  actual  starting  point  of 
the  investigation  which  ultimately  demonstrated  the  possibility  of 
human  flight  and  the  means  of  its  attainment,  dates  from  about  1888, 
when,  by  one  of  those  curious  coincidences  which  are  frequently 
observed  in  the  scientific  world,  several  highly-qualified  men  simul- 
taneously undertook  the  solution  of  the  problem  in  different  parts 
of  the  world.  They  were  Professor  Langley  in  America,  Maxim  in 
England,  Lilienthal  in  Germany,  and  Hargrave  in  Australia.  Pro- 


101 


.4  THEORY   OF   AVIATION 

fessor  Langley  first  began  his  investigation  of  the  laws  of  aeroplane 
flight  in  1887.  At  that  time,  he  built  the  now  famous  "whirling 
table,"  consisting  of  a  horizontal  rotating  arm  at  the  outer  end  of 
which  were  carried  the  planes  and  propellers  to  be  tested.  By  means 
of  ingenious  automatic  recording  devices,  the  lifting  power  of  dif- 
ferent forms  of  planes,  and  of  the  same  plane  at  different  angles  of 
incidence,  was  ascertained,  and  in  the  same  way  the  thrust  of  various 
types  of  propellers  was  recorded. 

The  complete  results  of  these  investigations  were  incorporated 
in  a  work  entitled  "Experiments  in  Aerodynamics,"  first  published 
in  1891.  Among  the  important  principles  established  was  that  of 
the  size  of  the  supporting  surface  as  governed  by  its  speed  of  travel. 
That  the  area  of  the  necessary  supporting  surface  in  an  aeroplane 
varies  inversely  as  the  square  of  the  velocity,  which  means  that  if 
a  biplane  requires  500  square  feet  of  supporting  surface  at  40  miles 
an  hour,  it  would  need  only  222  feet  at  60  miles  an  hour,  while  80 
square  feet  would  suffice  for  a  speed  of  100  miles  an  hour.  Langley 
explained  that  this  was  due  to  the  fact  that  at  the  higher  speeds, 
the  planes  passed  so  rapidly  on  to  new  and  undisturbed  bodies  of 
air,  that  there  was  not  sufficient  time  for  them  to  overcome  the 
inertia  of  the  air,  an  analogy  to  this  being  found  in  the  skater  on 
thin  ice,  who  does  not  remain  sufficiently  long  at  any  one  point  to 
break  through.  Of  all  the  scientists  who  undertook  the  solution  of 
the  problem,  Langley 's  work  was  undoubtedly  the  most  thorough, 
and  it  is  referred  to  more  at  length  later,  as  most  of  his  important 
results  were  achieved  a  few  years  later. 

Maxim.  Maxim,  in  1894,  undertook  the  construction  of  a 
huge  biplane,  though  it  bore  no  resemblance  to  any  of  the  machines 
of  this  type  of  the  present  day.  Fully  $100,000  was  expended  on 
the  project  and  the  latter  affords  an  excellent  example  of  the  wisdom 
of  the  policy  adopted  by  the  Wright  Brothers  at  the  inception  of 
their  first  serious  work.  They  realized  that  the  most  necessary  thing 
was  to  learn  how  to  fly — in  other  words,  how  to  control  an  aeroplane 
before  attempting  to  build  one.  Maxim  was  also  aware  of  the 
importance  of  this,  as  evidenced  by  the  fact  that  all  his  early 
experiments  were  made  with  the  machine  captive.  It  was  fitted 
with  wheels  running  on  wood  rails  and  supplementary  guard  rails 
were  designed  to  prevent  it  from  leaving  the  earth.  The  machine 


102 


THEORY   OF   AVIATION  5 

was  so  powerful,  however,  that  it  tore  away  from  the  latter  and  was 
smashed  in  alighting. 

Some  idea  of  the  size  of  the  Maxim  machine  may  be  conceived 
from  its  supporting  area  of  5,400  square  feet,  made  up  of  a  central 
rectangular  plane  directly  over  the  operating  platform;  forward, 
aft,  and  two  side  planes  at  the  same  level;  and  two  side  planes  at 
the  level  of  the  platform.  This  was  the  original  design,  subsequently 
reduced  to  4,000  square  feet  by  the  elimination  of  the  forward  and 
side  planes,  a  great  reduction  in  area  of  the  central  plane  and  a 
change  in  its  shape  to  a  rectangle  with  its  long  side  forward,  and 
the  addition  of  a  second  smaller  superimposed  plane,  making  it 
practically  a  biplane  with  the  machinery  and  operating  platform 
suspended  some  distance  below  it.  The  total  lift  of  the  planes  was 
10,000  pounds. 

The  internal  combustion  motor  not  having  been  developed  at 
that  time,  steam  was  employed  and  the  power  plant  was  of  a  most 
ingenious  order,  replete  with  novel  automatic  devices.  The  boiler 
was  of  the  water-tube  type,  the  light  copper  tubes  being  assembled 
in  the  form  of  a  triangle,  with  a  nest  of  additional  tubes  in  serpentine 
form  in  the  opening  of  the  latter,  giving  a  total  heating  surface  of 
about  800  square  feet,  with  a  "firebox"  surface  of  30  square  feet. 
Its  weight  with  a  feedwater  heater  and  gasoline  furnace  was  1,200 
pounds,  200  pounds  of  this  consisting  of  the  supply  of  water  itself. 
The  gasoline  fuel  was  heated  in  a  special  receptacle  and  was  delivered 
through  7,650  fine  j^ts  at  a  pressure  of  50  pounds  to  the  square  inch. 
A  number  of  ingenious  devices  were  employed  to  regulate  the  supply 
of  fuel  as  well  as  its  pre-heating  before  burning.  The  boiler  was 
designed  to  supply  steam  at  a  pressure  of  360  pounds  to  a  compound, 
condensing  engine  giving  360  horse-power. 

This  power  drove  two  propellers  17  feet  10  inches  in  diameter 
by  16  feet  pitch  at  375  r.p.m.  The  screw  thrust  before  starting 
reached  as  high  as  2,100  pounds,  Mr.  Maxim  having  calculated  that 
of  the  total  power,  150  horse-power  would  be  wasted  in  slip,  130 
horse-power  expended  in  actual  lift  on  the  angle  of  the  planes,  and 
80  horse-power  utilized  in  driving.  The  engine  cylinders,  frame,  and 
rods  were  all  of  sheet  steel  so  that  its  total  weight  was  only  600 
pounds,  setting  a  new  limit  at  that  time  of  2  pounds  per  horse-power. 
A  safety  device  led  the  high-pressure  steam  into  the  low-pressure 


103 


6  THEORY   OF   AVIATION 

cylinders  in  case  the  boiler  pressure  became  too  high,  this  increasing 
the  output  to  400  horse-power.  It  was  truly  a  case  of  Frankenstein 
being  overpowered  by  the  monster  he  himself  had  created,  as  shown 
by  the  subsequent  wrecking  of  the  machine.  Even  in  the  light  of 
present-day  knowledge,  few  aviators  would  care  to  attempt  the 
handling  of  such  a  huge  contrivance.  When  it  is  borne  in  mind  that 
the  cost  of  the  best  of  modern  aeroplanes  does  not  exceed  $8,000, 
it  seems  a  pity  that  such  a  sum  should  have  been  expended  at  a 
time  when  practical  results  would  have  done  so  much  for  the  develop- 
ment of  the  art. 

Langley's  Experiments.  Two  years  later,  or  in  1896,  Langley 
made  his  now  historic  experiments  with  steam-driven  models,  but 
before  referring  to  these  it  will  be  of  interest  to  note  for  how  much 
of  our  present  knowledge  his  early  investigations  were  responsible. 
To  give  these  at  length  from  his  own  works  would  involve  more 
space  than  is  available,  so  that  the  following  is  excerpted  from  an 
address  made  by  Prof.  Alexander  Graham  Bell,  the  inventor  of  the 
telephone,  on  the  occasion  of  the  presentation  of  the  Langley  medal 
to  the  Wright  Brothers,  February  10,  1910.  The  indebtedness  of 
the  latter  to  Langley's  work  is  fittingly  acknowledged  by  them  in 
their  own  story  of  their  experiments,  which  is  given  on  page  9. 

Langley's  experiments  in  aerodynamics  gave  to  physicists,  perhaps  for 
the  first  time,  firm  ground  on  which  to  stand  as  to  the  long-disputed  questions 
of  air  resistance  and  reactions.  Chanute  says: 

(1)  They  established  a  more  reliable  coefficient  for  rectangular  pressures 
than  that  of  Smeaton. 

(2)  They  proved  that  upon  inclined  planes  the  air  pressures  were  really 
normal  to  the  surface. 

(3)  They  disproved  the  Newtonian  law  that  the  normal  pressure  varied 
as  the  square  of  the  angle  of  incidence  on  inclined  planes. 

(4)  They  showed  that  the  empirical  formula  of  Duchemin  which  had 
been  proposed  in  1836  and  ignored  for  fifty  years,  was  approximately  correct. 

(5)  That  the  position  of  the  center  of  pressure  varied  with  the  angle  of 
inclination,  and  that  on  planes  its  movements  approximately  followed  the  law 
formulated  by  Joessel. 

(6)  That  oblong  planes,  presented  with  their  longest  dimension  in  the 
direction  of  motion,  were  more  effective  for  support  than  when  presented  with 
their  narrower  side. 

(7)  That  planes  might  be  superposed  without  loss  of  supporting  power 
if  spaced  apart  certain  distances  which  varied  with  the  speed. 

(8)  That  thin  planes  consumed  less  power  for  support  at  high  speeds 
than  at  low  speeds. 


104 


THEORY   OF   AVIATION  7 

The  paradoxical  result  obtained  by  Langley — that  it  takes  less  power 
to  support  a  plane  at  high  speed  than  at  low — opens  up  enormous  possibilities 
for  the  aerodrome  of  the  future.  It  results,  as  Chanute  has  pointed  out,  from 
the  fact  that  the  higher  the  speed,  the  less  need  be  the  angle  of  inclination  to 
sustain  a  given  weight,  and  the  less,  therefore,  the  horizontal  component  of 
the  air  pressure. 

It  is  true,  however,  only  of  the  plane  itself,  and  not  of  the  struts  and 
frame  work  that  go  to  make  up  the  rest  of  the  flying  machine.*  In  order, 


Fig.  1.     Langley 's  Aerodrome  Ready  for  a  Flight 

therefore,  to  take  full  advantage  of  Langley's  law,  those  portions  of  the  machine 
that  offer  head  resistance  alone,  without  contributing  anything  to  the  support 
of  the  machine  in  the  air,  should  be  reduced  to  a  minimum. 

After  laying  the  foundations  of  a  science,  Langley  proceeded  to  reduce 
his  theories  to  practice.  Between  1891  and  1895,  he  built  four  models,  one 
driven  by  carbonic-acid  gas  and  three  by  steam.  On  May  6,  1896,  his  aero- 
drome No.  5  was  tried  on  the  Potomac  River  near  Washington.  I  was  a  wit- 
ness of  this  experiment,  and  secured  photographs  of  the  machine  in  the  air, 
which  have  been  widely  published. 

This  aerodrome  carried  a  steam  engine  and  had  a  spread  of  wing  of  from 
12  to  14  feet.  It  was  shot  into  the  air  from  the  roof  of  a  house  boat  anchored 

*In  this  is  found  the  superiority  in  speed  of  the  monoplane  over  the  biplane. — Ed. 


105 


8  THEORY   OF   AVIATION 

in  a  quiet  bay  at  Quantico.  It  made  a  beautiful  flight  of  about  3,000  feet, 
considerably  over  half  a  mile.  It  was  indeed  a  most  inspiring  spectacle  to  see 
a  steam  engine  in  the  air,  flying  like  a  bird.  The  equilibrium  seemed  to  be 
perfect,  though  there  was  no  man  on  board  to  control  and  guide  the  machine. 
I  witnessed  two  flights  of  this  aerodrome  the  same  day  and  came  to  the  conclu- 
sion that  the  possibility  of  flight  by  heavier-than-air  machines  had  been  fully 
demonstrated.  The  world  took  the  same  view  and  the  progress  of  practical 
aerodromics  was  immensely  stimulated  by  the  experiments. 

Langley  afterward  constructed  a  number  of  other  aerodrome  models 
which  were  flown  with  equal  success,  and  he  then  felt  that  he  had  brought  his 
researches  to  a  conclusion  and  desired  to  leave  to  others  the  task  of  bringing 
the  experiments  to  the  man-carrying  stage.  Later,  however,  encouraged  by 
the  appreciation  of  the  War  Department,  which  recognized  in  the  Langley 
aerodrome  a  possible  new  engine  of  war,  and  stimulated  by  an  appropriation 
of  $50,000,  he  constructed  a  full-sized  machine  to  carry  a  man. 

Two  attempts  were  made,  with  Charles  Manleyas  the  aviator,  to  shoot 
the  machine  into  the  air  from  the  top  of  a  house  boat,  Fig.  1,  but  on  each 
occasion  it  caught  on  the  launching  ways  and  was  precipitated  into  the  water. 
The  public,  not  knowing  the  cause,  received  the  impression  that  the  machine 
itself  was  a  failure.* 

This  conclusion  was  not  warranted  by  the  facts,  and  to  me,  and  to  others 
who  examined  the  apparatus,  it  seemed  to  be  a  perfectly  good  flying  machine, 
excellently  constructed  and  the  fruit  of  years  of  labor.  It  was  simply  never 
launched  into  the  air,  and  so  has  never  had  an  opportunity  of  showing  what  it 
could  do.  Who  can  say  what  a  third  trial  might  have  demonstrated?  The 
general  ridicule,  however,  with  which  the  first  two  trials  were  greeted,  pre- 
vented any  further  appropriation,  f 

Langley's  faith  never  wavered,  but  he  never  saw  a  man-carrying  aero- 
drome in  the  air.  He  was  humiliated  by  the  ridicule  which  met  his  efforts 
and  never  recovered  from  his  disappointment,  which  hastened  his  death. 
His  greatest  achievements  in  practical  aerodynamics  consisted  in  the  success- 
ful construction  of  power-driven  models  which  actually  flew.J  With  their 
construction,  he  thought  he  had  finished  his  work,  and  in  1901,  in  announcing 
the  supposed  conclusion  of  his  labors,  he  said: 

"I  have  brought  to  a  close  the  portion  of  the  work  which  seemed  to  be 
specially  mine,  the  demonstration  of  the  practicability  of  mechanical  flight, 

*The  impression  was  fostered  by  the  press  for  the  reason  that  Langley  originally  would 
not  permit  the  presence  of  any  reporters.  He  later  consented,  but  the  numerous  delays  involved 
in  preparing  the  machine,  together  with  the  fact  that  little  information  was  volunteered  and 
the  gentlemen  in  question  were  utterly  incompetent  to  obtain  any  first  hand,  engendered  a 
hostile  attitude  on  their  part.  This  was  aggravated  by  tedious  hours  of  waiting  around  in 
skiffs  under  the  blazing  sun  for  something  in  the  nature  of  "copy"  to  happen,  so  that  they  were 
only  too  ready  to  seize  upon  an  opportunity  to  ridicule.  In  the  confusion  attendant  upon 
Manley's  second  spill  in  the  water,  no  attention  was  paid  to  the  machine  at  first,  and  it  was 
rescued  by  the  crew  of  a  tugboat.  Their  ignorance  of  its  construction  and  bungling  efforts 
resulted  in  wrecking  it  badly,  which  was  ascribed  by  the  press  to  its  fall  in  the  water,  which  had 
in  fact  not  damaged  it  particularly.  Hence,  the  widespread  report  that  it  was  an  utter  failure. 
—Ed. 

fThe  machine  has  been  preserved  and  there  is  a  movement  on  foot  to  put  it  in  commis- 
sion and  try  it. — Ed. 

JThese  machines  did  not  wreck  themselves  as  had  Ader's  machine  in  France,  and  Maxim's 
in  England. — Ed. 


106 


THEORY   OF   AVIATION 


and  for  the  next  stage,  which  is  the  practical  and  commercial  development 
of  the  idea,  it  is  probable  the  world  may  look  to  others." 

He  was  right,  and  the  others  have  appeared.  The  aerodrome  has 
reached  the  practical  and  commercial  stage;  and  chief  among  those  who  are 
developing  this  field  are  the  brothers,  Orville  and  Wilbur  Wright.  They  are 
eminently  deserving  of  the  highest  honor  from  us  for  their  great  achievements. 

Wright  Brothers'  Experiments.  So  many  and  varied  stories 
have  appeared  of  what  the  Wright  Brothers,  Fig.  2,  have  done  and 
how  they  did  it — many  of  them  largely  fiction  and  others  so  garbled 
as  to  be  scarcely  recognizable  by  those  about  whom  they  were  written 

—that  it  is  thought  advisable  to 
reproduce  here  verbatim  their  own 
account  of  their  exploits,  as  writ- 
ten by  them  and  published  in  the 
Century,  December,  1908.  This  is 
the  only  true  and  concise  report. 
"Our  personal  interest  in  the 
subject  of  aerial  navigation  dates 
from  our  childhood  days.  Late 
in  the  autumn  of  1878,  our  father 
came  into  the  house  one  evening 
with  some  object  partly  concealed 
in  his  hands,  and  before  we  could 
see  what  it  was,  he  tossed  it  into 
the  air.  Instead  of  falling  to  the 
floor,  as  we  expected,  it  flew  across 
the  room  until  it  struck  the  ceil- 
ing, where  it  fluttered  awhile,  and 
finally  sank  to  the  floor.  It  was  a 
little  toy,  known  to  scientists  as 
a  helicopter,  but  which  we,  with 
supreme  disregard  for  science,  at 
once  dubbed  a  'bat.'  It  was  a  light  frame  of  cork  and  bamboo, 
covered  with  paper,  which  formed  two  screws,  driven  in  opposite 
directions  by  rubber  bands  under  torsion.  A  toy  so  delicate  lasted 
only  a  short  time  in  the  hands  of  small  boys,  but  its  memory  was 
abiding. 

"Several  years  later,  we  began  building  these  helicopters  for 
ourselves,  making  each  one  larger  than  the  preceding.  But,  to  our 


Fig.  2.     Orville  and  Wilbur  Wright 


107 


10 


THEORY  OF  AVIATION 


astonishment,  we  found  that  the  larger  the  'bat'  the  less  it  flew. 
We  did  not  know  that  one  machine  having  only  twice  the  linear 
dimensions  of  another  would  require  eight  times  the  power.  We 
finally  became  discouraged  and  returned  to  kite-flying,  a  sport  to 
which  we  had  devoted  so  much  attention  that  we  were  regarded  as 
experts.  But  as  we  became  older,  we  had  to  give  up  this  fascinating 
sport  as  unbecoming  to  boys  of  our  ages. 

"It  was  not  until  the  sad  news  of  the  death  of  Lilienthal  reached 
America,  in  1896,  that  we  again  gave  more  than  passing  attention 
to  the  subject  of  flying.  We  then  studied  with  great  interest  Cha- 


Fig.  3.     Lilienthal's  Gliding  Apparatus 

nute's  'Progress  in  Flying  Machines/  Langley's  'Experiments  in 
Aerodynamics/  the  Aeronautical  Annuals  of  1895,  1896,  and  1897, 
and  several  pamphlets  published  by  the  Smithsonian  Institution, 
especially  articles  by  Lilienthal  and  extracts  from  Mouillard's 
'Empire  of  the  Air.'  The  larger  works  gave  us  a  good  under- 
standing of  the  nature  of  the  problem  of  flying,  and  the  difficulties 
in  past  attempts  to  solve  it,  while  Mouillard  and  Lilienthal,  the 
great  missionaries  of  the  flying  cause,  infected  us  with  their  own  un- 
quenchable enthusiasm  and  transformed  idle  curiosity  into  the  active 
zeal  of  workers. 


108 


THEORY   OF   AVIATION  11 

"In  the  field  of  aviation,  there  were  two  schools.  The  first, 
represented  by  such  men  as  Professor  Langley  and  Sir  Hiram  Maxim, 
gave  chief  attention  to  power  flight;  the  second,  represented  by 
Lilienthal,  Fig.  3,  Mouillard,  and  Chanute,  to  soaring  flight.  Our 
sympathies  were  with  the  latter  school,  partly  from  impatience  at 
the  wasteful  extravagance  of  mounting  delicate  and  costly  machinery 
on  wings  which  no  one  knew  how  to  manage,  and  partly,  no  doubt, 
from  the  extraordinary  charm  and  enthusiasm  with  which  the 
apostles  of  soaring  flight  set  forth  the  beauties  of  sailing  through  the 
air  on  fixed  wings,  deriving  the  motive  power  from  the  wind  itself. 

Balancing  Methods.  "The  balancing  of  a  flyer  may  seem,  at 
first  thought,  to  be  a  very  simple  matter,  yet  almost  every  experi- 
menter had  found  this  to  be  the  one  point  which  he  could  not  master. 
Many  different  methods  were  tried.  Some  experimenters  placed  the 
center  of  gravity  far  below  the  wings,  in  the  belief  that  the  weight 
would  naturally  seek  to  remain  at  the  lowest  point.  It  was  true, 
that,  like  the  pendulum,  it  tended  to  seek  the  lowest  point;  but  also, 
like  the  pendulum,  it  tended  to  oscillate  in  a  manner  destructive 
of  all  stability.  A  more  satisfactory  system,  especially  for  lateral 
balance,  was  that  of  arranging  the  wings  in  the  shape  of  a  broad  V 
to  form  a  dihedral  angle,  with  the  center  low  and  the  wing  tips  ele- 
vated. In  theory,  this  was  an  automatic  system,  but  in  practice  it 
had  two  serious  defects :  First,  it  tended  to  keep  the  machine  oscillat- 
ing; and  second,  its  usefulness  was  restricted  to  calm  air. 

"In  a  slightly  modified  form,  the  same  system  was  applied  to 
the  fore-and-aft  balance.  The  main  aeroplane  was  set  at  a  positive 
angle,  and  a  horizontal  tail  at  a  negative  angle,  while  the  center  of 
gravity  was  placed  far  forward.  As  in  the  case  of  lateral  control, 
there  was  a  tendency  to  constant  undulation,  and  the  very  forces 
which  caused  a  restoration  of  balance  in  calms,  caused  a  disturb- 
ance of  the  balance  in  winds.  Notwithstanding  the  known  limita- 
tions of  this  principle,  it  had  been  embodied  in  almost  every  promi- 
nent flying  machine  which  had  been  built. 

"After  considering  the  practical  effect  of  the  dihedral  principle 
we  reached  the  conclusion  that  a  flyer  founded  upon  it  might  be  of 
interest  from  a  scientific  point  of  view,  but  could  be  of  no  value  in  a 
practical  way.  We  therefore  resolved  to  try  a  fundamentally  dif- 
ferent principle.  We  would  arrange  the  machine  so  that  it  would 


109 


12 


THEORY   OF   AVIATION 


tend  to  right  itself.  We  would  make  it  as  inert  as  possible  to  the 
effects  of  change  of  direction  or  speed,  and  thus  reduce  the  effects 
of  wind  gusts  to  a  minimum.  We  would  do  this  in  the  fore-and- 
aft  stability  by  giving  the  aeroplanes  a  peculiar  shape;  and,  in  the 
lateral  balance,  by  arching  the  surfaces  from  tip  to  tip,  just  the  reverse 
of  what  our  predecessors  had  done.  Then  by  some  suitable  contriv- 
ance actuated  by  the  operator,  forces  should  be  brought  into  play  to 
regulate  the  balance. 

Working  Its  Planes.     "Lilienthal  and  Chanute  had  guided  and 
balanced  their  machines  by  shifting  the  weight  of  the  operator's 


Fig.  4.     An  Early  Wright  Glider  Showing  Horizontal  Front  Rudder 

body.  But  this  method  seemed  to  us  incapable  of  expansion  to  meet 
large  conditions,  because  the  weight  to  be  moved  and  the  distance 
of  possible  motion  were  limited,  while  the  disturbing  forces  steadily 
increased,  both  with  wing  area  and  wind  velocity.  In  order  to  meet 
the  needs  of  large  machines,  we  wished  to  employ  some  system 
whereby  the  operator  could  vary  at  will  the  inclination  of  the  different 
parts  of  the  wings,  and  thus  obtain  from  the  wind,  forces  to  restore 
the  balance,  which  the  wind  itself  had  disturbed.  This  could  easily 
be  done  by  using  wings  capable  of  being  warped,  and  by  supple- 


110 


THEORY   OF   AVIATION 


13 


mentary  adjustable  surfaces  in  the  shape  of  rudders.  As  the  forces 
obtainable  for  control  would  necessarily  increase  in  the  same  ratio 
as  the  disturbing  forces,  the  method  seemed  capable  of  expansion 
to  an  almost  unlimited  extent.  A  happy  device  was  discovered 
whereby  the  apparently  rigid  system  of  superposed  surfaces,  invented 
by  Wenham  and  improved  by  Stringfellow  and  Chanute,  could  be 
warped  in  a  most  unexpected  way,  so  that  the  aeroplanes  could  be 
presented  on  the  right  and  left  sides  at  different  angles  to  the  wind. 
This,  with  an  adjustable,  horizontal  front  rudder,  formed  the  main 
feature  of  our  first  glider,  Fig.  4. 


Fig.  5.     Flying  a  Glider  as  a  Kite  to  Study  its  Action 

"The  period  from  1885  to  1900  was  one  of  unexampled  activity 
in  aeronautics,  and  for  a  time  there  was  high  hope  that  the  age  of 
flying  was  at  hand.  But  Maxim,  after  spending  $100,000,  aban- 
doned the  work;  the  Ader  machine,  built  at  the  expense  of  the  French 
government,  was  a  failure;  Lilienthal  and  Pilcher  were  killed  in 
experiments;  and  Chanute  and  many  others,  from  one  cause  or 
another,  had  relaxed  their  efforts,  though  it  subsequently  became 
known  that  Professor  Langley  was  still  secretly  at  work  on  a  machine 
for  the  United  States  government.  The  public,  discouraged  by  the 
failures  and  tragedies  just  witnessed,  considered  flight  beyond  the 


111 


14  THEORY   OF  AVIATION 

reach  of  man,  and  classed  its  adherents  with  the  would-be  inventors 
of  perpetual  motion. 

"We  began  our  active  experiments  at  the  close  of  this  period, 
in  October,  1900,  at  Kitty  Hawk,  North  Carolina.  Our  machine 
was  designed  to  be  flown  as  a  kite,  with  a  man  on  board,  in  winds 
from  15  to  20  miles,  an  hour.  But,  upon  trial,  it  was  found  that 
much  stronger  winds  were  required  to  lift  it.  Suitable  winds  not 
being  plentiful,  we  found  it  necessary,  in  order  to  test  the  new  bal- 
ancing system,  to  fly  the  machine  as  a  kite  without  a  man  aboard, 
operating  the  levers  through  chords  from  the  ground,  Fig.  5.  This 


Fig.  6.     Testing  the  Balance  of  a  Glider  with  a. Man  Aboard 

did  not  give  the  practice  anticipated  but  it  inspired  confidence  in 
the  new  system  of  balance. 

"In  the  summer  of  1901,  we  became  personally  acquainted  with 
Chanute.  When  he  learned  that  we  were  interested  in  flying  as 
a  sport,  and  not  with  any  expectation  of  recovering  the  money 
we  were  expending  upon  it,  he  gave  us  much  encouragement.  At 
our  invitation,  he  spent  several  weeks  with  us  at  our  camp  at  Kill 
Devil  Hill,  four  miles  south  of  Kitty  Hawk,  during  our  experiments 
of  that  and  two  succeeding  years.  He  also  witnessed  one  flight  of 
the  power-driven  machine  near  Dayton,  Ohio,  in  October,  1904. 

"The  machine  of  1901  was  built  with  the  shape  of  surface  used 
by  Lilienthal,  curved  from  front  to  rear  like  the  segment  of  a  parabola, 


112 


THEORY   OF  AVIATION  15 

with  a  curvature  of  one-twelfth  the  depth  of  its  chord;  to  make 
sure  that  it  would  have  sufficient  lifting  capacity  when  flown  as  a 
kite  in  15-  or  20-mile  winds,  we  increased  the  area  from  165  square 
feet,  used  in  1900,  to  308  square  feet — a  size  much  larger  than  Lilien- 
thal,  Pilcher,  or  Chanute  had  deemed  safe.  Upon  trial,  however, 
the  lifting  capacity  again  fell  very  far  short  of  calculation,  so  that 
the  idea  of  securing  practice  while  flying  as  a  kite,  had  to  be  aban- 
doned. Chanute,  who  witnessed  the  experiments,  told  us  that 
the  trouble  was  not  due  to  poor  construction  of  the  machine.  We 


Fig.  7.     Glider  with  Vertical  Rear  Rudder 


saw  only  one  other  explanation — that  the  tables  of  air  pressures  in 
general  use  were  incorrect. 

Gliding  Experiments.  "We  then  turned  to  gliding — coasting 
down  hill  on  the  air — as  the  only  method  of  getting  the  desired 
practice  in  balancing  a  machine,  Fig.  6.  After  a  few  minutes 
practice  we  were  able  to  make  glides  of  over  300  feet,  and  in  a  few 
days  were  safely  operating  in  27-mile  winds.  The  gliding  flights 
were  all  made  against  the  wind.  The  difficulty  in  high  winds  is  in 
maintaining  balance,  not  in  traveling  against  the  wind.  In  these 
experiments  we  met  with  several  unexpected  phenomena.  We  found 
that,  contrary  to  the  teachings  of  the  books,  the  center  of  pressure 
on  a  curved  surface  traveled  backward  when  the  surface  was  inclined, 
at  small  angles,  more  and  more  edgewise  to  the  wind.  We  also  dis- 
covered that  in  free  flight,  when  the  wing  on  one  side  of  the  machine 
was  presented  to  the  wind  at  a  greater  angle  than  the  one  on  the 


113 


16  THEORY   OF   AVIATION 

other  side,  the  wing  with  the  greater  angle  descended,  and  the 
machine  turned  in  a  direction  just  the  reverse  of  what  we  were  led 
to  expect  when  flying  the  machine  as  a  kite.  The  larger  angle  gave 
more  resistance  to  forward  motion,  and  reduced  the  speed  of  the  wing 
on  that  side.  The  decrease  in  speed  more  than  counterbalanced  the 
effect  of  the  larger  angle.  The  addition  of  a  fixed  vertical  vane,  Fig. 
7,  in  the  rear  increased  the  trouble  and  made  the  machine  absolutely 
dangerous.  It  was  some  time  before  a  remedy  was  discovered.  This 
consisted  of  movable  wings  working  in  conjunction  with  the  twisting 
of  the  wings.  The  details  of  this  arrangement  are  given  in  our  patent 
specifications,  published  several  years  ago.* 

Verification  of  Pressure  Constants.  "The  experiments  of  1901 
were  far  from  encouraging.  Although  Chanute  assured  us  that 
both  in  control  and  weight  carried  per  horse-power,  the  results 
obtained  were  better  than  those  of  any  of  our  predecessors,  yet  we 
saw  that  the  calculations  on  which  all  flying  machines  had  been  based 
were  unreliable,  and  that  every  experimenter  was  simply  groping 
in  the  dark.  Having  set  out  with  absolute  faith  in  the  existing 
scientific  data,  we  were  driven  to  doubt  one  thing  after  another, 
till  finally,  after  two  year$  of  experiment,  we  cast  it  all  aside  and 
decided  to  rely  entirely  upon  our  own  investigations.  Truth  and 
error  were  everywhere  so  intimately  mixed  as  to  be  indistinguish- 
able. Nevertheless,  the  time  expended  in  the  preliminary  study  of 
books  was  not  misspent,  for  they  gave  us  a  good  general  under- 
standing of  the  subject  and  enabled  us  at  the  outset  to  avoid  effort 
in  many  directions  in  which  results  would  have  been  hopeless. 

"The  standard  for  measurements  of  wind  pressures  is  the  force 
produced  by  a  current  of  air  of  1-mile-per-hour  velocity  striking 
against  a  plane  of  1  square  foot  area.  The  practical  difficulty  of 
obtaining  an  exact  measurement  of  this  force  has  been  great.  The 
measurements  by  different  recognized  authorities  vary  50  per  cent. 
When  this  simplest  of  measurements  presents  so  great  difficulties, 
what  shall  be  said  of  the  troubles  encountered  by  those  who  attempt 
to  find  the  pressure  at  each  angle  as  the  plane  is  inclined  more  and 
more  edgewise  to  the  wind?  In  the  eighteenth  century,  the  French 
Academy  prepared  tables  giving  such  information,  and  at  a  later  date 
the  Aeronautical  Society  of  Great  Britain  made  similar  experiments. 

*See  pages  65  and  75,  Aeronautical  Practice,  Part  II. 


114 


THEORY   OF   AVIATION  17 

Many  persons  likewise  published  measurements  and  formulas;  but 
the  results  were  so  discordant  that  Professor  Langley  undertook  a 
new  series  of  measurements,  the  results  of  which  form  the  basis  of  his 
celebrated  work  'Experiments  in  Aerodynamics/  Yet  a  critical 
examination  of  the  data  upon  which  he  based  his  conclusions  as  to 
pressures  at  small  angles  shows  results  so  various  as  to  make  many 
of  his  conclusions  little  better  than  guesswork. 

"To  work  intelligently,  one  needs  to  know  the  effects  of  a  mul- 
titude of  variations  that  could  be  incorporated  in  the  surfaces  of 
flying  machines.  The  pressures  on  squares  are  different  from  those 
on  rectangles,  circles,  triangles,  or  ellipses;  arched  surfaces  differ 
from  planes,  and  vary  among  themselves  according  to  the  depth  of 
curvature;  true  arcs  differ  from  parabolas,  and  the  latter  differ 
among  themselves;  thick  surfaces  differ  from  thin,  and  surfaces 
thicker  in  one  place  than  another  vary  in  pressure  when  the  positions 
of  maximum  thickness  are  different;  some  surfaces  are  most  efficient 
at  one  angle,  others  at  other  angles.  The  shape  of  the  edge  also 
makes  a  difference,  so  that  thousands  of  combinations  are  possible 
in  so  simple  a  thing  as  a  wing. 

"We  had  taken  up  aeronautics  merely  as  a  sport.  We  reluc- 
tantly entered  on  the  scientific  side  of  it.  But  we  soon  found  the 
work  so  fascinating  that  we  were  drawn  into  it  deeper  and  deeper. 
Two  testing  machines  were  built,  which  we  believed  would  avoid 
the  errors  to  which  the  measurements  of  others  had  been  subject. 
After  making  preliminary  measurements  on  a  great  number  of  sur- 
faces to  secure  a  general  understanding  of  the  subject,  we  began 
systematic  measurements  of  standard  surfaces  so  varied  in  design 
as  to  bring  out  the  underlying  causes  of  differences  noted  in  their 
pressures.  Measurements  were  tabulated  on  nearly  fifty  of  these 
at  all  angles  from  zero  to  45  degrees,  at  intervals  of  2J  degrees. 
Measurements  were  also  secured  showing  the  effects  on  each  other 
when  surfaces  are  superposed,  or  when  they  follow  one  another. 

"Some  strange  results  were  obtained.  One  surface,  with  a  heavy 
roll  at  the  front  edge,  showed  the  same  lift  for  al  angles  from  7J  to 
45  degrees.  A  square  plane,  contrary  to  the  measurements  of  all 
our  predecessors,  gave  a  greater  pressure  at  30  degrees  than  at  45 
degrees.  This  seemed  so  anomalous  that  we  were  almost  ready  to 
doubt  our  own  measurements  when  a  simple  test  was  suggested.  A 


115 


18 


THEORY   OF   AVIATION 


weather  vane  with  two  planes  attached  to  the  pointer  at  an  angle  of 
80  degrees  with  each  other  was  made.  According  to  our  tables,  such 
a  vane  would  be  in  unstable  equilibrium  when  pointing  directly  into 
the  wind;  for  if,  by  chance,  the  wind  should  happen  to  strike  one 
plane  at  39  degrees  and  the  other  at  41  degrees,  the  plane  with 
the  smaller  angle  would  have  the  greater  pressure,  and  the  pointer 
would  be  turned  still  further  out  of  the  course  of  the  wind  until 
the  two  vanes  again  secured  equal  pressures,  which  would  be 
approximately  at  30  and  50  degrees.  But  the  vane  performed  in 
this  very  manner.  Further  corroboration  of  the  tables  was  ob- 
tained in  the  experiments  with  a  new  glider  at  Kill  Devil  Hill  the 

next  season. 

"In  September  and  Octo- 
ber, 1902,  nearly  1,000  glid- 
ing flights  were  made,  several 
of  which  covered  distances  of 
over  600  feet  (all  made  with 
the  operator  lying  prone  as 
shown  in  Fig.  8).  Some  glides 
against  a  wind  of  36  miles  an 
hour  gave  proof  of  the  effec- 
tiveness of  the  devices  for 
control.  With  this  machine, 
in  the  autumn  of  1903,  we 
made  a  number  of  flights  in 
which  we  remained  in  the 
air  for  over  a  minute,  often  soaring  for  a  considerable  time  in 
one  spot  without  any  descent  at  all.  Little  wonder  that  our  un- 
scientific assistant  should  think  the  only  thing  needed  to  keep 
it  in  the  air  indefinitely  would  be  a  coat  of  feathers  to  make  it 
light! 

"With  accurate  data  for  making  calculations,  and  a  system  of 
balance  effective  in  winds  as  well  as  in  calms,  we  were  now  in  a  posi- 
tion, we  thought,  to  build  a  successful  power  flyer.  The  first  designs 
provided  for  a  total  weight  of  600  pounds,  including  the  operator 
and  an  8-horse-power  motor.  But  upon  completion,  the  motor  gave 
more  power  than  had  been  estimated,  and  this  allowed  150  pounds 
for  strengthening  the  wings  and  other  parts. 


Fig.  8.     Gliding  Flight,  Showing  Prone  Position 
of  Operator 


116 


THEORY   OF   AVIATION  19 

Propeller  Design.  "Our  tables  made  the  designing  of  the  wings 
an  easy  matter;  and  as  screw  propellers  are  merely  wings  traveling 
in  a  spiral  course,  we  anticipated  no  trouble  from  this  source.  We 
had  thought  of  getting  the  theory  of  the  screw  propeller  from  the 
marine  engineers,  and  then,  by  applying  our  tables  of  air  pressures 
to  their  formulas,  of  designing  air  propellers.  But  so  far  as  we 
could  learn,  the  marine  engineers  possessed  only  empirical  formulas, 
and  the  exact  action  of  the  screw  propeller,  after  a  century  of  use, 
was  still  very  obscure.  As  we  were  not  in  a  position  to  undertake  a 
long  series  of  practical  experiments  to  discover  a  propeller  suitable 
for  our  machine,  i^  seemed  necessary  to  obtain  such  a  thorough  under- 
standing'of  the  theory  of  its  reactions  as  would  enable  us  to  design 
them  from  calculation  alone.  What  at  first  seemed  a  simple  problem, 
became  more  complex  the  longer  we  studied  it.  With  the  machine 
moving  forward,  the  air  flying  backward,  the  propellers  turning  side- 
wise,  and  nothing  standing  still,  it  seemed  impossible  to  find  a  starting 
point  from  which  to  trace  the  various  simultaneous  reactions.  Con- 
templation of  it  was  confusing.  After  long  arguments,  we  often 
found  ourselves  in  the  ludicrous  position  of  each  having  been  con- 
verted to  the  other's  side,  with  no  more  agreement  than  when  the 
discussion  began. 

"It  was  not  until  several  months  had  passed,  and  every  phase 
of  the  problem  had  been  threshed  over  and  over,  that  the  various 
reactions  began  to  untangle  themselves.  When  once  a  clear  under- 
standing had  been  obtained  there  was  no  difficulty  in  designing  suit- 
able propellers,  with  proper  diameter,  pitch,  and  area  of  blade,  to 
meet  the  requirements  of  the  flyer.  High  efficiency  in  a  propeller 
is  not'  dependent  upon  any  particular  or  peculiar  shape,  and  there  is 
no  such  thing  as  a  best  screw.  A  propeller  giving  a  high  dynamic 
efficiency  when  used  upon  one  machine,  may  be  almost  worthless 
when  used  upon  another.  The  propeller  should  in  every  case  be 
designed  to  meet  the  particular  conditions  of  the  machine  to  which 
it  is  to  be  applied.  Our  first  propellers,  built  entirely  from  calcula- 
tion, gave  in  useful  work  66  per  cent  of  the  power  expended.  This  was 
about  one-third  more  than  had  been  secured  by  Maxim  or  Langley. 

First  Power  Flight.  "The  first  flights  with  the  power  machine 
were  made  on  the  17th  of  December,  1903.  Only  five  persons  beside 
ourselves  were  present.  These  were  Messrs.  John  T.  Daniels,  W.  S. 


117 


20 


THEORY   OF   AVIATION 


Dough,  and  A."  D.  Etheridge  of  the  Kill  Devil  life  saving  station; 
W.  C.  Brinkley  of  Manteo;  and  John  Ward  of  Naghead.  Although 
a  general  invitation  had  been  extended  to  the  people  living  within 
5  or  6  miles,  not  many  were  willing  to  face  the  rigors  of  a  cold  Decem- 
ber wind  in  order  to  see,  as  they  no  doubt  thought,  another  flying 
machine  not  fly.  The  first  flight  lasted  only  12  seconds,  a  flight  very 
modest  compared  with  that  of  birds,  but  it  was,  nevertheless,  the 


Fig.  9.     One  of  the  First  Power  Flights  of  the  Wright  Biplane 

first  in  the  history  of  the  world  in  which  a  machine  carrying  a  man 
had  raised  itself  by  its  own  power  into  the  air  in  free  flight,  had 
sailed  forward  on  a  level  course  without  reduction  in  speed,  and  had 
finally  landed  without  being  wrecked.  The  second  and  third  flights 
were  a  little  longer,  and  the  fourth  lasted  59  seconds,  covering  a 
distance  of  853  feet  over  the  ground  against  a  20-mile  wind,  Fig.  9. 
"After  the  last  flight,  the  machine  was  carried  back  to  camp 
and  set  down  in  what  was  thought  to  be  a  safe  place.  But  a  few 
minutes  later,  while  we  were  engaged  in  conversation  about  the 


THEORY   OF   AVIATION  21 

flights,  a  sudden  gust  of  wind  struck  the  machine  and  started  to  turn 
it  over.  All  made  a  rush  to  stop  it  but  we  were  too  late.  Daniels, 
a  giant  in  stature  and  strength,  was  lifted  off  his  feet  and,  falling 
inside  between  the  surfaces,  was  shaken  about  like  a  rattle  in  a  box 
while  the  machine  rolled  over  and  over.  He  finally  fell  out  upon  the 
sand  with  nothing  worse  than  painful  bruises,  but  the  damage  to  the 
machine  caused  a  discontinuancce  of  the  experiments. 

"In  the  spring  of  1904,  through  the  kindness  of  Torrence 
Huffman  of  Dayton,  Ohio,  we  were  permitted  to  erect  a  shed  and 
continue  experiments,  on  what  is  known  as  the  Huffman  prairie,  at 
Simms  Station,  eight  miles  from  Dayton.  The  new  machine  was 
heavier  and  stronger  but  similar  to  the  one  flown  at  Kill  Devil  Hill. 
When  it  was  ready  for  its  first  trial,  every  newspaper  in  Dayton  was 
notified,  and  about  a  dozen  representatives  of  the  press  were  present. 
Our  only  request -was  that  no  pictures  be  taken  and  that  the  reports 
be  unsensational,  so  as  not  to  attract  crowds  to  our  experiment 
grounds.  There  were  probably  40  persons  altogether  on  the  ground. 
When  preparations  were  completed,  a  wind  of  only  3  or  4  miles  an 
hour  was  blowing — insufficient  for  starting  on  so  short  a  track — 
but  since  so  many  had  come  a  long  way  to  see  the  machine  in  action, 
an  attempt  was  made.  To  add  to  the  other  difficulty,  the  engine 
refused  to  work  properly.  The  machine,  after  running  the  length 
of  the  track,  slid  off  without  rising  into  the  air  at  all.  Several  of  the 
newspaper  men  returned  the  next  day  but  were  again  disappointed. 
The  engine  again  performed  badly  and  after  a  glide  of  only  60  feet, 
the  machine  came  to  the  ground.  Further  trial  was  postponed  until 
the  engine  could  be  put  in  better  condition.  The  reporters  had  now, 
no  doubt,  lost  confidence  in  the  machine,  though  their  reports,  in 
kindness,  concealed  it.  Later,  when  they  heard  that  we  were  making 
flights  of  several  minutes'  duration,  knowing  that  longer  flights  had 
been  made  in  airships,  and  not  knowing  any  essential  difference 
between  airships  and  flying  machines,  they  were  but  little  interested. 

"We  had  not  been  flying  long  in  1904  before  we  found  that  the 
problem  of  equilibrium  had  not  as  yet  been  entirely  solved.  Some- 
times, in  making  a  circle,  the  machine  would  turn  over  edgewise 
in  spite  of  anything  the  operator  could  do,  although,  under  the  same 
conditions  in  ordinary  straight  flight,  it  could  have  been  righted  in 
an  instant.  In  one  flight,  in  1905,  while  circling  around  a  honey 


119 


22 


THEORY   OF   AVIATION 


locust  tree  at  a  height  of  about  50  feet,  the  machine  suddenly 
began  to  turn  up  on  one  wing  and  took  a  course  toward  the  tree. 
The  operator,  not  relishing  the  idea  of  landing  in  a  thorn  tree, 
attempted  to  reach  the  ground.  The  left  wing,  however,  struck 
the  tree  at  a  height  of  10  or  12  feet  from  the  ground  and  carried 
away  several  branches;  but  the  flight,  which  had  already  covered  a 
distance  of  6  miles,  was  continued  to  the  starting  point. 

"The  causes  of  these  troubles,  too  technical  for  explanation  here, 
were  not  entirely  overcome  till  the  end  of  September,  1905.  The 
flights  then  rapidly  increased  in  length,  till  experiments  were  dis- 


Fig.  10.     Preparing  the  Machine  for  the  Start 

continued,  after  the  5th  of  October,  on  account  of  the  number  of 
people  attracted  to  the  field.  Although  made  on  a  ground  open  on 
every  side,  and  bordered  on  two  sides  by  much  traveled  thorough- 
fares, with  electric  cars  passing  every  hour,  and  seen  by  all  people 
living  in  the  neighborhood  for  miles  around,  and  by  several  hundred 
others,  yet  these  flights  have  been  made  by  some  newspapers  the 
subject  of  a  great  'mystery.' 

"A  practical  design  having  been  finally  realized,  we  spent  the 
years  1906  and  1907  in  constructing  new  machines  and  in  business 
negotiations.  It  was  not  until  May  of  this  year  (1908)  that  experi- 
ments (discontinued  in  October,  1905)  were  resumed  at  Kill  Devil 


120 


THEORY   OF   AVIATION  23 

Hill,  North  Carolina.  The  recent  flights  were  made  to  test  the  ability 
of  our  machine  to  meet  the  requirements  of  a  contract  with  the 
United  States  government  to  furnish  a  flyer  capable  of  carrying  two 
men  and  sufficient  fuel  and  supplies  for  a  flight  of  125  miles,  with  a 
speed  of  40  miles  an  hour.  The  machine  used  in  these  tests  was  the 
same  one  with  which  the  flights  were  made  at  Simms  Station  in  1905, 
though  several  changes  had  been  made  to  meet  present  requirements. 
The  operator  assumed  a  sitting  position,  instead  of  lying  prone  as  in 
1905,  and  a  seat  was  added  for  a  passenger.  A  larger  motor  was 


Fig.  11.     Starting  Device  Used  with  the  Early  Wright  Machines 

installed,  and  radiators  and  gasoline  reservoirs  of  larger  capacity 
replaced  those  previously  used.  No  attempt  was  made  to  make  high 
or  long  flights. 

Management  of  an  Aeroplane.  "In  order  to  show  the  general 
reader  the  way  in  which  the  machine  operates,  let  us  fancy  ourselves 
ready  for  the  start,  Fig.  10.  The  machine  is  placed  upon  a  single 
rail  track  facing  the  wind  and  is  securely  fastened  with  a  cable, 
Fig.  11.*  The  engine  is  put  in  motion  and  the  propellers  in  the  rear 
whir.  You  take  your  seat  at  the  center  of  the  machine  beside  the 
operator.  He  slips  the  cable  and  you  shoot  forward.  An  assistant, 

*Now  obsolete  through  adoption  of  wheeled  chassis. — Ed. 


121 


24  THEORY   OF   AVIATION 

who  has  been  holding  the  machine  in  balance  on  the  rail,  starts  for- 
ward with  you  but  before  you  have  gone  50  feet  the  speed  is  too 
great  for  him,  and  he  lets  go.  Before  reaching  the  end  of  the  track, 
the  operator  moves  the  front  rudder  and  the  machine  lifts  from 
the  rail  like  a  kite  supported  by  the  pressure  of  the  air  underneath  it. 
The  ground  under  you  at  first  is  a  perfect  blur,  but  as  you  rise  objects 
become  clearer.  At  a  height  of  100  feet  you  feel  hardly  any  motion 
at  all,  except  for  the  wind  which  strikes  your  face.  If  you  did  not 
take  the  precaution  to  fasten  your  hat,  you  have  probably  lost  it  by 
this  time.  The  operator  moves  a  lever;  the  right  wing  rises,  and  the 
machine  swings  about  to  the  left.  You  make  a  very  short  turn,  yet 
do  not  feel  the  sensation  of  being  thrown  from  your  seat,  so  often 
experienced  in  automobile  and  railway  travel.  You  find  yourself 
facing  toward  the  point  from  which  you  started.  The  objects  on 
the  ground  now  seem  to  be  moving  at  a  much  higher  speed,  though 
you  perceive  no  change  in  the  pressure  of  the  wind  on  your  face.  You 
know  then  that  you  are  traveling  with  the  wind.  When  you  near 
the  starting  point,  the  operator  stops  the  mofor  while  still  high  in 
the  air.  The  machine  coasts  down  at  an  oblique  angle  to  the  ground, 
and,  after  sliding  50  to  100  feet,  comes  to  rest.  Although  the  machine 
often  lands  when  traveling  at  a  speed  of  a  mile  a  minute  you  feel  no 
shock  whatever,  and  can  not,  in  fact,  tell  the  exact  moment  at  which 
it  first  touched  the  ground.  The  motor  beside  you  kept  up  an  almost 
deafening  roar  during  the  whole  flight,  yet  in  your  excitement  you 
did  not  notice  it  until  it  stopped. 

"Our  experiments  have  been  conducted  entirely  at  our  expense. 
In  the  beginning,  we  had  no  thought  of  recovering  what  we  were 
expending,  which  was  not  great  and  was  limited  to  what  we  could 
afford  for  recreation.  Later  when  a  successful  flight  had  been  made 
with  a  motor,  we  gave  up  the  business  in  which  we  were  engaged, 
to  devote  our  entire  time  and  capital  to  the  development  of  a  machine 
for  practical  uses.  As  soon  as  our  condition  is  such  that  constant 
attention  is  not  required,  we  expect  to  prepare  for  publication  the 
results  of  our  laboratory  experiments,  which  alone  made  an  early 
solution  of  the  flying  problem  possible." 

United  States  Government  Requirements.  The  War  Depart- 
ment had  called  for  bids  on  heavier-than-air  flying  machines,  and 
three  aeroplanes  were  accepted  for  trial.  The  Wright  machine  was 


122 


THEORY   OF   AVIATION  25 

one  of  these,  and  the  others  were  submitted,  one  by  A.  M.  Herring, 
and  the  other  by  James  F.  Scott.  The  official  tests  took  place  dur- 
ing the  early  part  of  September,  1908,  at  Fort  Meyer,  Virginia,  across 
the  Potomac  from  Washington.  The  Wright  flyer  was  the  only  one 
of  this  type  of  flying  machine  to  take  part,  although  the  Baldwin 
dirigible  fulfilled  the  conditions  required  of  it  and  was  accepted,  as 
has  been  mentioned  before. 

The  conditions  imposed  by  the  War  Department  were  generally 
believed  by  experts  to  be  impossible  of  fulfillment.  It  was  demanded 
that  the  machine  should  make  an  endurance  flight  of  one  hour;  that 
it  should  have  a  speed  of  40  miles  an  hour  in  still  air;  that  it  should 
be  able  to  carry  sufficient  fuel  for  a  flight  of  125  miles;  and  that  it 
should  be  capable  of  carrying  two  persons  with  a  combined  weight 
of  360  pounds.  Three  tests  for  speed  and  three  for  endurance  were 
to  be  allowed. 

It  was  required  that  during  the  endurance  flight  the  aeroplane 
should  remain  continuously  in  the  air  for  one  hour,  that  it  should  be 
under  perfect  control,  and  that  it  should  return  to  the  starting  point 
and  alight  without  mishap.  Further,  it  was  demanded  that  the 
machine  should  be  so  designed  as  to  be  assembled  and  ready  for 
operation  within  60  minutes — the  apparatus  being  of  such  construc- 
tion as  to  be  readily  taken  apart,  transported  in  a  couple  of  wagons, 
and  put  together  again  whenever  wanted  for  service. 

If  these  conditions  were  met,  the  government,  it  was  under- 
stood, would  pay  $25,000  for  the  machine.  They  certainly  seemed 
next  to  impossible,  and  nobody — least  of  all  the  army  officers 
appointed  to  supervise  the  trial — imagined  that  they  could  be  ful- 
filled. Only  the  Wrights  themselves  were  confident.  The  machine 
offered  for  test  was  a  new  machine,  never  flown,  and  its  construction 
embraced  some  novel  features,  the  most  important  being  a  modifica- 
tion which  enabled  the  aviator  to  sit  erect. 

Tests  of  1908.  On  September  9,  Orville  Wright  made  a  con- 
tinuous flight  of  36  miles,  staying  in  the  air  57  minutes  and  31  seconds. 
That  evening,  he  made  another  flight  of  38J  miles  in  1  hour,  2  minutes, 
and  15  seconds.  This  not  only  broke  all  records  but  was  a  flight  of 
over  twice  the  duration  of  any  previously  made.  He  then  took 
Lieutenant  Lahm  of  the  United  States  Army  as  a  passenger  for  a 
short  trip. 


123 


26  THEORY   OF   AVIATION 

Three  days  later  he  stayed  in  the  air  1  hour  and  14  minutes, 
making  a  speed  of  nearly  29  miles  per  'hour.  No  attempts  at  great 
altitudes  were  made,  250  feet  being  about  the  greatest  height 
attained. 

A  deplorable  accident  occurred  on  September  17,  which  showed 
that  the  flyer  was  not  yet  proof  against  mechanical  defects.  On  this 
trip,  Orville  Wright  took  Lieutenant  Selfridge  with  him  as  passenger. 
When  they  were  preparing  to  descend,  after  a  very  successful  flight, 
one  of  the  propellers  caught  in  a  stay  wire  and  snapped.  The  machine 
fell  to  the  ground,  pinning  the  aviators  under  it.  Lieutenant  Self- 
ridge  was  killed,  and  Wright  received  rather  severe,  but  temporary, 
injuries.  This  accident  prevented  the  completion  of  the  govern- 
ment tests. 

Wilbur  Wright  in  Europe.  In  France.  Meantime,  Wilbur 
Wright,  in  France,  was  preparing  to  give  demonstrations  of  his 
machine  with  a  view  to  selling  his  French  patents.  At  first  he  was 
not  regarded  very  seriously  in  that  country,  and  the  'French  comic 
papers  hailed  him  as  "le  Bluff eur"  They  quickly  acknowledged 
their  mistake  when,  on  September  21,  he  made  a  continuous  flight 
of  over  an  hour  and  a  half  at  Le  Mans. 

World's  Record  Broken.  On  the  last  day  of  the  year  1908, 
Wilbur  Wright  won  the  Michelin  prize  and  $4,000  in  cash,  and  made 
a  new  world's  flying  record  of  2  hours,  18  minutes,  and  33  seconds; 
official  distance  covered,  77  miles  and  760  yards;  actual  distance, 
making  allowance  for  the  distance  lost  in  turns,  about  95  miles — 
the  longest  flight  ever  made  by  a  heavier-than-air  machine.  Because 
of  his  success  in  France/  Wilbur  Wright  sold  his  French  patents  to 
the  Astra  Company. 

Flights  in  Italy.  During  March  and  April,  1909,  Wright  made 
some  successful  flights  in  Italy  for  the  War  Department.  He  taught 
some  of  the  Italian  officers  the  art,  but  his  pupils  still  had  something 
to  learn,  as  one  of  them  had  an  accident  due  to  faulty  steering.  Wil- 
bur Wright  sold  his  Italian  rights  to  a  syndicate  which  is  manu- 
facturing his  machines  for  military  and  other  purposes. 

United  States  Government  Requirements  Fulfilled.  In  the 
latter  part  of  June,  1909,  Orville  Wright,  assisted  by  his  brother, 
again  attempted  to  fulfill  the  conditions  imposed  by  the  LTnited  States 
War  Department.  The  trials  were  made  at  Fort  Meyer,  Virginia, 


124 


THEORY   OF   AVIATION  27 

as  were  those  of  the  year  before.  A  new  motor  was  used  and  his 
early  attempts  were  unsuccessful,  because  the  engine  had  not  been 
thoroughly  tested. 

In  later  attempts  the  machine  failed  to  rise  properly,  and  the 
inventors  turned  their  attention  to  the  starting  power.  They  added 
about  sixty  pounds  to  the  weight  which  gives  the  initial  momentum, 
dug  a  deep  pit  to  give  the  weight  a  longer  fall,  and  lengthened  the 
starting  rail  by  about  12  feet.  This  seemed  to  remedy  the  trouble, 
for  no  further  difficulty  was  encountered.  On  July  20,  a  new  Ameri- 
can record  was  established,  Orville  Wright  remaining  in  the  air  over 
1  hour  and  20  minutes. 

The  first  part  of  the  government  requirements  were  met  a  week 
later,  when  Orville  Wright  made  a  flight  of  nearly  an  hour  and  a 
quarter — carrying  a. passenger — at  a  speed  averaging  about  40  miles 
per  hour.  Incidentally,  this  broke  his  brother's  best  record  for  a 
flight  with  passenger  made  in  France  the  year  before. 

On  July  30,  Orville  Wright  met  the  last  test  of  his  aeroplane  at 
Fort  Meyer,  and  for  the  first  time  in  its  history  the  government  became 
possessor  of  a  flying  machine.  On  a  straightaway  course  of  5  miles 
out  and  return,  with  a  passenger,  Lieut.  Benjamin  D.  Foulois,  Wright 
maintained  a  speed  of  something  over  42  miles  an  hour,  and  won 
for  himself  and  brother,  in  addition  to  the  $25,000  contract  price 
of  the  machine,  a  bonus  of  more  than  $5,000.  The  elapsed  time 
of  the  flight,  according  to  the  official  figures,  was  14  minutes  and 
42  seconds.  ^ 

The  conditions  of  the  speed  test  were  as  simple  as  they  were 
severe.  The  aeroplane  was  required  to  fly  5  miles  straightaway  from 
the  Fort  Meyer  parade  grounds  to  and  around  an  army  balloon 
anchored  at  the  end  of  the  course  and  back  to  the  starting  point. 
For  every  mile  of  speed  less  than  40  miles  an  hour,  a  penalty  of  10 
per  cent  on  the  contract  price  of  the  aeroplane  was  to  be  deducted 
from  that  price,  and  for  every  mile  in  excess  of  40  miles  an  hour 
attained  during  the  flight,  a  bonus  of  10  per  cent  was  to  be  added. 
A  speed  of  less  than  36  miles  an  hour  meant  the  rejection  of  the 
machine. 

The  course  was  over  an  exceedingly  rough  and  dangerous  country, 
so  far  as  affording  safe  landing  places  for  a  flying  machine  was  con- 
cerned, as  it  was  made  up  of  hills,  valleys,  and  thick  woods  for  almost 


125 


28  THEORY  OF  AVIATION 

the  entire  distance.  In  addition  to  the  landing  difficulties  the 
many  air  currents  made  this  particularly  treacherous  territory. 

The  5-mile  limit  was  marked  by  a  small  army  balloon  anchored 
on  Shuter's  Hill,  2  miles  back  of  Alexandria.  Another  balloon  at 
Four  Mile  Run  marked  the  middle  of  the  course  and  served  as  a  guide 
to  the  aeronauts.  A  field  telephone  was  established  between  Shuter's 
Hill  and  the  starting  line. 

Orville  Wright  established  a  new  world  record  for  aeroplanes  in 
cross-country  flying.  No  aeroplane  had  ever  before  flown  across  a 
country  as  rough  and  broken  as  lay  under  this  course,  and  never 


Fig.  12.     Silver  Dart,  a  Successful  Model  of  the  Aerial  Experiment  Association 

before  had  a  flight  of  equal  distance  been  attempted  by  any  aero- 
plane carrying  two  persons.  Other  cross-country  flights  had  been 
made  in  France,  but  the  conditions  were  more  favorable. 

Aerial  Experiment  Association.  An  organization  which  has 
accomplished  a  greal  deal  that  is  of  experimental  value  during 
its  short  life,  was  the  Aerial  Experiment  Association  at  Hammonds- 
port,  New  York.  This  was  composed  of  such  enthusiasts  as  Dr. 
Alexander  Graham  Bell,  Glenn  H.  Curtiss,  Lieutenant  Selfridge 
(who  met  his  death  in  the  accident  at  Fort  Meyer),  and  others. 
The  association  was  organized  in  1907  and  lasted  till  1909.  Aside 
from  the  tests  of  Dr.  Bell's  tetrahedral  kites,  a  most  successful  type 
of  aeroplane  was  developed,  the  Silver  Dart,  illustrated  in  Fig.  12, 
being  one  of  the  several  machines  produced. 


126 


THEORY   OF   AVIATION 


29 


There  are  two  distinctive  features  in  the  design.  The  first  is 
the  general  principle  and  arrangement  of  the  truss  which  supports 
the  two  surfaces,  being  a  double  bowstring  truss,  which  was  found 
to  have  structural  advantages  over  the  flat-bridge  design  commonly 
used.  The  other  features  which  distinguish  the  machine  from  the 
usual  type  of  double-deck  machines  lie  in  the  shape  of  the  support- 
ing surfaces,  which  are  very  much  like  a  bird's  wing  in  plan,  tapering 
toward  the  tips,  and  at  the  same  time  decreasing  in  curvature. 

Red  Wing.  The  Association's  first  aeroplane,  the  Red  Wing, 
flew  318  feet  above  Lake  Keuka  on  March  12,  1908.  It  has  almost 


Fig.  13.     June  Bug,  an  A.  E.  A.  Machine 

the  same  construction  as  the  White  Wing  (which  will  be  described 
in  detail),  except  that  it  was  mounted  on  runners.  On  its  first  flight 
the  tail  of  the  Red  Wing  buckled.  This  was  a  horizontal  single- 
surface  tail,  and  was  then  changed  to  a  two-surface  box  shape  much 
like  that  used  on  the  Farman  aeroplanes.  In  a  flight  a  few  days  later, 
the  aeroplane  tipped  and  fell  on  the  ice  and  was  completely  demol- 
ished. 

White  Wing.  The  next  machine,  the  White  WTing,  was  mounted 
on  bicycle  wheels.  A  wood  propeller  was  used  with  an  eight-cylinder, 
40-horse-power,  air-cooled  Curtiss  gasoline  engine.  The  diameter  of 
the  propeller  was  a  little  over  6  feet.  The  aeroplane  was  42  feet  6 


127 


30 


THEORY   OF  AVIATION 


inches  long  from  tip  to  tip,  and  4  feet  deep  at  the  outside  panel.  It 
had  a  total  supporting  area  of  408  square  feet,  and  weighed  430 
pounds.  A  box-shaped  tail  like  that  used  last  on  the  Red  Wing  was 
mounted  in  the  rear,  and  in  the  middle  was  a  vertical  rudder.  A 
double-surface  horizontal  rudder  was  placed  in  front.  The  wing 
tips  were  pivoted  at  their  forward  edges  and  made  to  move  up  and 
down  slightly  by  means  of  a  cord  attached  to  the  aviator's  body.  It 
was  thought  that  the  instinctive  leaning  of  the  aviator  to  one  side  in 
making  turns  could  be  made  to  set  the  wings  properly. 


Fig.  14.     View  of  Power  Plant  of  Silver  Dart,  J.  A.  D.  McCurdy  at  the  Wheel 

On  one  attempt,  the  White  Wing  covered  over  1,000  feet.  It  was 
driven  by  G.  H.  Curtiss,  and  was  his  first  flight.  The  machine 
touched  earth  once  after  covering  about  600  feet,  but  at  once  rose 
and  continued  for  another  400  feet. 

June  Bug.  The  next  machine  was  the  June  Bug,  shown  in  Fig. 
13.  In  its  construction,  the  June  Bug  had  the  two  main  superposed 
surfaces,  with  a  spread  of  42  feet  6  inches,  including  wing  tips,  and 
with  a  total  supporting  surface  of  370  square  feet.  The  motor  was  of 
25  horse-power,  with  8  cylinders,  and  a  speed  of  1 ,000  revolutions  per 
minute.  The  total  weight  of  the  machine  with  motor  was  650  pounds. 


128 


THEORY   OF   AVIATION 


31 


Silver  Dart.  The  June  Bug  was  superseded  by  the  Silver  Dart 
built  under  the  direction  of  J.  A.  D.  McCurdy,  of  the  Aerial  Experi- 
ment Association,  who  is  seen  at  the  wheel  in  Fig.  14.  It  made  its  first 
successful  flight  at  the  grounds  of  the  Association  at  Stony  Brook  Farm 
on  December  15,  1908.  There  were  several  trials,  all  of  which  proved 
satisfactory. 

In  the  Silver  Dart,  the  propeller  was  placed  differently  than  in 
earlier  machines.  Not  only  was  a  forward  motion  for  the  whole 
machine  obtained  by  the  new  arrangement,  but  a  buoyant  or  lifting 
effect  was  also  produced.  The  engine  was  of  a  similar  design  to  the 


Fig.  15.     Behavior  of  a  Stationary  Plane  in  a  Current  of  Air  According 
to   Newton's  Ideas 

June  Bug,  but  of  twice  the  horse-power.  An  excellent  view  of  the 
installation  of  the  engine  and  propeller  is  given  in  Fig.  14.  The  total 
weight  of  the  Silver  Dart,  including  its  burden,  a  man  weighing,  say 
150  pounds,  was  860  pounds. 

Herring=Curtiss  Company.  The  success  attained  by  the  machines 
of  the  Aerial  Experiment  Association,  and  especially  the  Silver  Dart, 
was  attracting  wide-spread  attention  in  Europe,  and  it  was  feared 
that,  as  in  the  case  of  the  Wright  Brothers,  the  benefits  of  these 
inventions  would  go  to  Europe.  To  prevent  this,  Courtland  Field 
Bishop,  president  of  the  Aero  Club  of  America,  formed  a  company, 
in  which  the  interests  of  Glenn  H.  Curtiss  and  A.  M.  Herring  were 
combined.  Curtiss'  motorcycle  and  aeronautic  motor  factory  was 
taken  over  by  this  company,  and  afforded  an  excellent  base  for 
beginning  operations.  Herring  claims  to  own  basic  patents  on  the 


129 


32 


THEORY   OF   AVIATION 


only  solution  of  anything  approaching  automatic  control  of  aero- 
planes so  far  proven  practicable.  With  the  organization  of  the 
Herring-Curtiss  Company  came  the  dissolution  of  the  Aerial  Experi- 
ment Association. 


ELEMENTARY  AERODYNAMICS 

Air  Resistance.  While  an  extended  study  of  the  theoretical 
side  of  flight  would  involve  going  deeply  into  mathematics  and 
would  in  itself  require  a  volume  for  its  exposition,  it  is  essential  for 
the  student  to  know  at  least  the  principles  upon  which  flight  is 
based;  especially  as  applied  to  the  design  of  the  successful  aeroplanes. 
The  most  important  single  factor  is  the  resistance  of  the  air,  and  a 
knowledge  of  its  bearing  upon  aviation,  particularly  in  the  considera- 
tion of  the  pressure  on  the  surface  of  an  aeroplane,  is  fundamental. 

Although  it  has  been  the 
subject  of  study  for  cen- 
turies, it  has  been  only 
within  comparatively  recent 
times  that  either  the  true 
nature  of  the  atmosphere, 
or  reliable  data  concerning 
its  action,  has  been  form- 
ulated. For  instance,  Sir 
Isaac  Newton,  in  his  "Prin- 
cipia,"  defines  air  as  an  "elastic,  non-continued,  rare  medium  con- 
sisting of  equal  particles  freely  disposed  at  equal  distances  from 
each  other."  In  accordance  with  this,  if  A B,  Fig.  15,  is  a  section 
of  a  surface  against  which  a  stream  of  air  is  blowing,  all  the 
particles  of  air  strike  directly  against  the  surface,  as  indicated 
by  the  arrows.  In  contrast  with  this,  Newton  defined  water,  oil, 
etc.,  as  "continued  mediums,"  in  which  all  the  particles  generating 
the  resistance  do  not  come  in  immediate  contact  with  the  surface. 
The  latter  is  pressed  upon  only  by  the  particles  that  lie  next  to  it; 
these  in  turn  being  pressed  by  those  beyond,  and  so  on.  The  char- 
acter of  this  fluid  pressure  is  shown  by  Fig.  16,  and  subsequent 
investigators  in  demonstrating  the  fallacy  of  Newton's  theory,  show 
that  air,  as  a  medium,  is  similar  in  character  to  water,  so  that  Fig.  16 


Fig.  16.     Correct  Idea  of  Air  Currents  Set  Up 
by  a  Plane 


130 


THEORY   OF   AVIATION  33 

also  illustrates  the  action  of  a  stream  of  air  in  striking  a  flat  surface 
held  at  right  angles  to  its  course. 

Newton  calculated  that  the  resistance  of  a  "continued  medium" 
varies  in  the  "duplicate  ratio  of  the  velocity,"  and  directly  as  the 
density  of  the  medium  itself.  Robins,  in  1746,  with  a  view  to  deter- 
mining the  resistance  of  the  air  to  cannon  balls,  whirled  planes  and 
spheres  about  a  circular  orbit,  and  found  that  the  resistance  varied 
directly  as  the  square  of  the  velocity.  This  was  also  determined 
to  be  true  in  various  ways  by  later  experimenters,  Rennie  having  so 
abundantly  verified  this  relation  for  low  velocities  in  1830,  that  it 
has  since  been  accepted  without  question. 

Constant  K  of  Air  Resistance.  But  to  accurately  calculate  the 
pressure  on  a  given  surface,  we  must  have  another  factor  and  that  is 
the  density  of  the  medium  pressing  against  the  surface.  There  is  a 
great  deal  of  variance  between  different  investigators  regarding  the 
value  of  this  factor,  but  once  it  is  known,  the  resistance  of  the  air 
may  be  expressed  in  terms  of  pounds  pressure  by  the  following 
formula : 

Pressure  equals  constant  X  area  X  velocity  squared 
or 

P=KAV* 

where  K  is  the  "constant  of  air  resistance,"  the  value  of  which  depends 
upon  the  density  (barometric  pressure)  and  temperature  of  the  air 
and  the  character  of  the  surface  of  the  plane.  This  equation  may  be 
derived  from  the  la\^s  of  mechanics  as  follows: 

Let  W  equal  the  weight  of  the  air  directed  against  any  normal 
surface  in  a  given  time;  w  equal  weight  in  pounds  of  one  cubic  foot 
of  air;  V  equal  velocity  of  the  air  stream  in  feet  per  second;  A  equal 
area  of  surface  on  which  pressure  acts ;  M  equal  mass  of  air  of  weight 
W;  g  equal  acceleration  due  to  gravity,  or  32.2  feet  per  second;  and 
P  equal  pressure  on  the  area  A.  Then  the  total  weight  W  will  equal 
the  product  of  the  weight  of  the  total  number  of  cubic  feet  w,  times 
the  area,  times  the  velocity,  or 

W=wAV 

But  the  momentum  of  the  force  on  the  area  is  equivalent  to 
the  mass  times  its  velocity ;  and  if  A  be  assumed  to  equal  one  square 
foot,  ic  equals  0.0807  pounds,  or  the  weight  of  air  per  cubic  foot  at 


131 


34  THEORY   OF   AVIATION 

32°  F.  and  30  inches  barometric  pressure,  and  V  may  be  expressed 
in  miles  per  hour.  Then,  since  VP  =  MV, 

P  =  .0054  V2 

K  thus  taking  the  theoretical  value  .0054  where  F^is  expressed  in 
miles  per  hour  and  P  in  pounds  per  square  foot. 

In  1759,  Smeaton  deduced  the  formula  P=.005  F2,  and  con- 
sidering A  as  unity,  he  published  a  table  of  velocity  and  pressure  of 
the  wind.  His  actual  value  for  K  was  .00492,  but  it  early  became 
customary  in  engineering  practice  to  take  it  as  .005.  This  table  was 
regarded  as  a  standard  in  engineering  textbooks  for  years,  but  as 
long  since  it  has  been  shown  to  be  erroneous,  it  is  not  given  here. 

Numerous  other  investigators  have  deduced  the  value  of 
A"  as  ranging  all  the  way  from  .0025  to  .0055.  In  1842  Colonel 
Duchemin  derived  it  as  .00492  and  published  the  results  of  a  thorough 
series  of  experiments  which  have  proved  very  valuable.  Early 
investigators  erred,  however,  in  the  method  of  making  their  experi- 
ments which  were  conducted  writh  the  aid  of  a  revolving  member  or 
"whirling  table,"  and  overlooked  the  disturbing  effects  of  the  cyclonic 
action  thus  set  up.  The  values  deduced  by  more  recent  experimenters 
employing  surfaces  either  held  rigid  against  the  stream  of  air,  or 
moved  directly  into  it,  are  as  follows : 

Col.  Renard  1887  #  =  .00348 

Langley  1888  K  =  .00389  to  .00320 

Lilienthal  1889  #  =  .005 

Voisin  1900  K  =  .0025 

Wright  Brothers  1901  #  =  .0033 

Eiffel  1903  K  -.0031 

Eiffel  was  among  the  first  to  recognize  two  sources  of  inaccuracy 
—the  neglect  of  the  consideration  of  separate  air  filaments  which 
vary  at  different  points  on  the  surface,  and  the  cyclonic  action  of  the 
air  due  to  a  revolving  source.  His  experiments  were  carried  out  on 
the  Eiffel  Tower.  The  surface  was  attached  to  a  carriage  by  springs, 
the  pressure  being  recorded  on  a  blackened  cylinder.  The  carriage 
was  allowed  to  fall  vertically  about  312  feet  and  was  constrained  in 
its  motion  by  a  vertical  cable. 

The  coefficient  K  varied  remarkably  little  and  was  practically 
determined  as  .0031.  He  also  found,  that  between  700  and  1,300 
feet  per  second  the  pressure  was  proportional  to  the  square  of  the 


132 


THEORY   OF   AVIATION 


35 


Fig.  17.      Diagram  Showing  Lift  and 
Drift  of  a  Plane 


velocity,  but  that  at  about  1,300  feet  per  second,  it  began  to  increase 
and  vary  as  the  cube.  As  it  is  unlikely  that  aeroplanes  will  ever 
reach  such  velocities,  this  is  a 
factor  that  need  not  be  con- 
sidered. 

Out  of  the  vgreat  number  of 
experiments  of  this  kind,  con- 
ducted in  various  ways,  those 
carried  out  on  the  Berlin-Zossen 
electric  line  in  1903  are  un- 
doubtedly the  most  accurate 
as  well  as  the  best  applicable 
to  the  actual  conditions  of  a 

large  body  moving  through  the  air  at  high  speed.  Velocities  as  high 
as  120  miles  an  hour  were  attained  and  the  air  resistance  carefully 
measured  by  an  elaborate  set  of  pressure  gauges.  The  mean  value 
of  the  results  as  plotted  on  a  chart  gave  P  =  .0027  V2. 

Comparing  the  result  of  grouping  the  values  as  determined  in 
three  different  ways  and  taking  their  average,  we  have 

(1)  K  =  .0054  (by  theory) 

(2)  X  =  .0042  (by  rotating  apparatus) 

(3)  K  =  .0029  (by  movement  in  a  straight  line) 

For  the  purpose  of  calculations  of  pressures  on  an  aeroplane, 
the  third  is  naturally  the  most  accurate,  so  that  for  figuring  air  pres- 
sures as  applied  to  aeroplanes,  the  most  practical  expression  of  such 
pressure  is  P=.003^4F2,  where  /v=.003. 


Fig.  18.     Disturbances  Caused  in  Air  by  a  Plane  at  a  Small  Angle  of  Incidence 

Air  Pressure  on   Moving  Surfaces.     Plane  Surfaces.    This  is 
the  starting  point  in  all  aeroplane  calculations.     Next  comes  the 


133 


36 


THEORY   OF   AVIATION 


action  of  different  forms  of  surfaces  when  moved  forward  through 
the  air.  Investigations  of  this  phase  of  the  subject  also  date  back 
to  Newton,  but  a  great  deal  of  the  work  of  early  experimenters  was 
shown  to  be  wrong  by  Langley,  who  verified  Duchemin's  neglected 
formula  of  1842. 

Assuming  Pa  to  represent  the  pressure  acting  perpendicularly 
to  the  surface  of  a  plane  inclined  at  an  angle  in  a  wind  current  of 
velocity  V,  we  may  resolve  it  into  two  components  at  right  angles; 
one  acting  perpendicularly  and  equal  to  L,  and  another  acting  hori- 


Fig.  19.     Disturbances  Caused  in  Air  by  a  Curved  Plane  at  a  Small  Angle  of  Incidence 

zontally  and  equal  to  D,  Fig.  17.     In  the  present  terminology  of 
aerodynamics,  L  is  termed  the  lift  and  D  the  drift  of  a  plane.     Then 


and 


Z>=Pasin  a 
L  =Pn  cos  a 


This  was  resolved  as  early  as  1809  by  Sir  George  Cayley  and  has 
since  been  verified  by  Langley  and  by  actual  practice.  The  ratio  of 
these  two  quantities  LD,  termed  the  ratio  of  lift  to  drift,  is  the  means 
of  expressing  the  aerodynamic  efficiency  of  the  supporting  surface  of 
an  aeroplane. 

Curved  Surfaces.  Up  to  Lilienthal's  time  all  experiments  had 
been  made  with  flat  surfaces  and  as  the  result  of  his  study  of 
birds'  wings,  he  was  the  first  to  recognize  that  even  very  slight 
curvatures  of  the  plane  profile  (section)  considerably  increased  the 
lifting  power.  The  reactions  and  disturbances  of  flat  and  curved 
planes  traveling  through  the  air  are  graphically  illustrated  by  Figs. 
18  and  19.  In  a  flat  plane,  the  pressure  is  always  perpendicular 


134 


THEORY   OF   AVIATION 


37 


to  the  surface  and,  as  already  pointed  out,  the  ratio  of  lift  to  drift  is, 
therefore,  as  the  cosine  to  the  sine  of  the  angle  of  incidence.  The  angle 
of  incidence  is  the  angle  at  which  the  plane  is  inclined  to  the  air 
current.  But  in  curved  surfaces,  Fig.  20,  as  first  shown  by  Lilienthal, 
the  pressure  is  not  uniformly  normal  to  the  chord  of  the  arc,  but  is 


Fig.  20.      Resolution  of  Force  Diagram  for  a  Curved  Plane 

considerably  inclined  forward  of  the  perpendicular,  with  the  result 
that  the  lift  is  increased  and  the  drift  decreased.  He  stated  it  as 
follows  : 

When  a  wing  with  an  arched  surface  is  struck  by  the  wind  at  an  angle 
a  with  a  velocity  V,  there  will  be  generated  a  pressure  P,  which  is  not  normal, 
but  is  the  resultant  of  a  force  N,  normal  to  the  chord,  and  of  another  force  T, 
tangential  to  the  cho^d. 

Taking  A  as  the  area  of  the  wing,  and  .005  as  the  coefficient  of  air  resist- 
ance, it  is  apparent  that  — 


T  =  IX.W5XAXV2 

Values  of  n  and  t,  which  represent  constants  used  by  Lilienthal,  show 
the  arched  surfaces  still  possess  supporting  powers  when  the  angle  of  incidence 
becomes  negative,  i.e.,  below  the  horizontal.  The  air  pressure  P  becomes  a 
propelling  force  at  angles  exceeding  3  degrees  up  to  30  degrees. 

As  Chanute  pointed  out,  this  does  not  mean  that  there  is  no 
horizontal  component,  or  drift,  of  the  normal  pressure  N  under 
these  conditions,  but  that,  at  certain  angles,  the  tangential  pressure 
T,  which  would  be  parallel  to  the  surface  and  only  produce  friction 
in  the  case  of  a  flat  plane,  acts  on  a  curved  surface  as  a  propelling 
force.  The  experiments  of  the  Wright  Brothers  at  Kitty  Hawk, 


135 


38  THEORY   OF   AVIATION 

North  Carolina,  verified  the  existence  of  Lilienthal's  tangential, 
and  experiments  conducted  by  them  later  in  their  laboratory  further 
supported  this  fact,  though  their  results  differed  from  Lilienthal's 
at  angles  below  10  degrees.  Fig.  20  illustrates  the  resolution  of  forces 
on  a  curved  plane,  L  and  D  being  the  lift  and  drift  as  obtained  from 
the  effective  pressure  AT. 

Lilienthal  prepared  a  table  giving  the  values  of  n  and  t  on  an 
inclined  surface,  on  a  basis  of  •£?  curve  from  zero  to  90  degrees,  and 
a  comparison  of  this  with  the  experiments  of  Langley  on  flat  surfaces 
exhibits  at  once  the  greater  lifting  effect  of  curved  surfaces,  though 
Wilbur  Wright  is  of  the  opinion  that  Lilienthal's  values  are  some- 
what too  large  at  angles  below  9  degrees.  Although  many  excellent 
treatises  have  been  written  on  the  subject,  it  is  hardly  possible  with 
the  present  knowledge  of  aerodynamics  to  explain  exactly  what 
the  significance  of  these  values  n  and  t  are,  or  to  bring  them  under 
any  well-known  set  of  physical  laws. 

An  examination  of  the  photographs  of  stream  lines  of  air  obtained 
by  such  experimenters  as  Marey,  Hele-Shaw,  and  Mach  and  Akborn, 
suggests  that  a  surface  with  a  pronounced  curve  at  the  front  would 
tend  to  produce  a  vortex  action  under  the  front  edge,  when  the  cur- 
rent of  air  is  swift  enough,  and  recent  investigations  indicate  that 
such  action  increases  the  dynamic  resistance  enormously  as  the  speed 
increases.  In  racing  machines,  therefore,  the  curved  surface  so 
widely  used  in  slower  machines  is  being  gradually  departed  from 
and  in  its  stead,  a  surface  with  a  flat  under  side  and  a  curved  upper 
side,  having  considerable  thickness  at  the  center,  is  being  substituted. 
The  air  stream  is  thus  guided  smoothly  over  the  upper  curved  surface, 
while  the  lower  flat  face  permits  of  a  much  easier  flow,  and  con- 
sequently of  a  decrease  of  dynamic  resistance,  or  drift.  The  decrease 
in  the  lift  thus  occasioned  is  compensated  for  by  higher  velocities  due 
to  increased  motor  power.  Just  how  much  the  lift  is  decreased  can  be 
shown  only  by  actual  practice.  This  flattening  of  the  under  side  of 
the  supporting  surface  has  a  great  disadvantage  in  that  it  tends 
greatly  to  lessen  the  stability  of  the  machine. 

Ratio  of  Lift  to  Drift.  The  ratio  of  lift  to  drift  is  of  great  impor- 
tance in  the  design  of  aeroplanes,  and  the  surface  having  the  greatest 
ratio  under  working  conditions  is  the  most  efficient  from  an  aero- 
dynamic standpoint,  i.e.,  it  carries  the  greatest  weight  with  the 


136 


Ht/MB£ft  (LOVELACE] 
MOHOPLAHE 


CHGfffi  6'-6" 

Fig.  21. 


Sections  of  Main  Supporting  Planes  of  Well-Known  Types  of 
Aeroplanes  Shown  in  London,  1910 


137 


*-, 


40  THEORY   OF   AVIATION 

least  power.  The  large  value  of  the  ratio  for  small  angles  shows  arched 
surfaces  to  be  the  most  economical  in  flight.  The  manner  in  which 
various  prominent  designers  have  worked  out  the  problem  in  actual 
practice  is  illustrated  by  the  comparison  of  the  different  sections  of 
the  supporting  surfaces,  or  planes,  of  the  machines  exhibited  at 
Olympia,  London,  1910,  Fig.  21.  The  experiments  on  the  relation 
of  sustaining  power  to  head  resistance,  on  various  planes,  show  that 
a  thick,  curved  plane  is  very  efficient,  as  well  as  by  far  the  most 
stable.  The  Antoinette  monoplane  is  equipped  with  surfaces  of 

this  form.  (See  upper  dia- 
gram, Fig.  28,  in  "Types  of 
Aeroplanes.") 

Aspect  Ratio.  "Aspect 
ratio"  is  the  term  commonly 
employed  to  indicate  the  ratio 
of  spread,  i.  e.,  width  of  the 
supporting  surfaces,  to  their 
depth.  It  is  a  feature  of 
greater  importance  than  the 
curvature  of  the  plane  itself, 
in  that  it  determines  to  a 
considerable  extent  the  lifting 
power  of  the  latter.  At  first 
glance,  it  would  seem  that  a 
given  area  of  surface  at  a  certain  angle  of  incidence  and  moving  at 
a  stated  speed  would  produce  a  definite  lifting  reaction,  regardless 
of  the  plan  form  of  the  surface.  This  is  not  the  case,  however,  as 
can  be  simply  demonstrated.  The  plan  form  and  its  aspect  or  direc- 
tion of  presentation  are  items  of  the  greatest  importance  in  deter- 
mining the  lifting  power  per  unit  of  area.  Obviously,  the  lifting  or 
supporting  reaction  of  the  air  upon  a  surface  depends  upon  the 
amount  of  air  displaced  or  acted  upon  by  it  in  a  unit  of  time.  Fig. 
22  shows  three  equal  surfaces  of  rectangular  plan  form,  varying  in 
their  respective  ratios  of  width  to  length,  the  length  being  in  each 
case  measured  parallel  to  the  line  or  axis  of  flight. 

If  each  of  the  three  surfaces  shown,  A,  B,  and  C,  is  given  the 
same  angle  of  incidence  and  is  moved  along  its  line  of  flight  at  the 
same  speed,  the  amount  of  air  acted  upon  in  unit  time  (the  measure 


Fig.  22.     Aspect  Ratio  of  Planes 


138 


THEORY   OF   AVIATION  41 

of  the  relative  supporting  powers)  will  naturally  vary  among  the 
three  surfaces  as  the  width  of  the  presented  edge.  That  is,  for  equal 
rectangular  areas  of  supporting  surface,  at  the  same  speed  and  angle 
of  incidence,  the  supporting  powers  vary  as  the  ratios  of  the  widths 
to  lengths  along  the  axes  of  flight.  In  Fig.  22,  then,  if  the  surface 
A  will  support  1  pound,  B  will  support  .5  pound  and  C  will  support 
4  pounds,  all  other  conditions  being  identical.  Of  course,  these  fig- 
ures are  modified  considerably  by  the  heights  and  depths  to  which 
the  air  is  acted  upon  by  the  passage  of  the  surfaces,  and,  since  these 
values  vary  directly  but  in  reduced  ratios,  as  the  axial  lengths  of  the 
compared  surfaces,  it  will  be  apparent  that  C  will  not  actually  lift 
eight  times  as  much  weight  as  B.  However,  the  rate  of  gain  is  very 
much  higher  than  the  rate  of  loss,  as  the  width  or  spread  is  extended 
and  the  depth  correspondingly  decreased,  as  strikingly  shown  by 
the  simple  comparison  just  given.  In  the  case  of  plane  A,  the  aspect 
ratio  is  1  to  1 ;  in  B  it  is  .5  to  1,  or  what  might  be  termed  a  negative 
aspect  ratio;  in  C  it  is  4  to  1.  By  referring  to  "Types  of  Aeroplanes," 
it  will  be  noted  that  the  usual  aspect  ratio  employed  in  actual  prac- 
tice varies  between  5  and  7  to  1. 

As  a  matter  of  fact,  the  efficiency  of  the  supporting  reaction 
increases  almost  indefinitely  with  an  extension  of  the  width  to  length 
ratio  and  in  practice  is  limited  only  by  constructional  considerations. 
This  is  shown  in  nature  by  the  extremely  great  spread  of  wing  of 
the  soaring  birds  as  compared  with  their  depth.  For  instance,  the 
man-of-war  hawk,  ai  tropical  marine  bird,  has  a  spread  of  wing  of 
several  feet  while  its  depth  is  but  a  few  inches  (plane  C).  It  is  very 
rarely  seen  to  move  its  wings  in  flight,  but  soars  practically  motionless 
at  altitudes  of  several  hundred  to  a  thousand  feet.  The  common 
black  crow  of  northern  latitudes,  on  the  other  hand,  has  a  wing 
more  closely  approximating  plane  B,  considering  the  upper  edge  of  this 
to  be  the  one  presented  to  the  air,  instead  of  the  left-hand  edge  as 
in  the  illustration.  Birds  of  this  class  are  slow  and  heavy  fliers  and 
have  to  flap  their  wings  constantly. 

Weight  for  weight,  the  structure  of  surface  B  can  be  made 
stronger  than  A,  even  as  A  is  inherently  stronger  than  C,  and  the 
limit  of  extension  of  the  aspect  ratio  is  determined  only  by  strength 
considerations  in  the  completed  surface.  Average  practice  in  this 
respect  places  the  ratio  at  about  6  to  1. 


139 


42 


THEORY   OF   AVIATION 


Skin  Friction.  By  analogy  with  the  great  frictional  resistance 
of  a  body  in  water,  it  would  seem  as  if  the  friction  of  the  air  would 
also  be  considerable.  This  is  termed  skin  friction  and,  in  their  experi- 
ments, many  early  investigators  put  it  down  as  practically  a  negligible 
factor.  Professor  Zahn  went  into  this  thoroughly  in  1903  and  deter- 
mined that  the  friction  of  the  air  on  surfaces  is  an  important  factor. 
He  expressed  its  general  value  in  the  formula  F=  .0000158  L-^v  1>05, 
where  F  is  the  frictional  drag  in  pounds  per  square  foot,  L  is  the 
length  of  the  surface  in  the  direction  of  motion  in  feet,  and  v  is  the 
velocity  of  the  air  past  the  surface  in  miles  per  hour.  The  friction 
was  found  to  be  approximately  the  same  for  all  smooth  surfaces, 

but  10  to  15  per  cent  greater 
on  extremely  rough  surfaces, 
which  accounts  for  the  care  with 
which  the  supporting  surfaces  of 
an  aeroplane  are  made  smooth. 
It  is  now  generally  accepted  that 
skin  friction  is  an  appreciable 
factor  in  the  resistance  of  an 
aeroplane,  amounting  to,  in  an 
average-sized  machine,  from  10 
to  15  pounds. 

In  his  experiments  to  deter- 
mine head  resistance  and  skin 
friction,  Langley  employed  a  ro- 
tating table  with  a  collapsible  arm  holding  a  straight  plane  cutting 
edge  of  a  given  area,  which  could  be  moved  at  different  speeds.  He 
found  that  256  square  feet  of  skin-frictional  surface  developed  ap- 
proximately 1  pound  resistance  at  a  speed  of  30  miles  an  hour.  It 
was  also  found  that  cutting  edges  with  straight  surfaces  and  sharp 
angles  developed  almost  double  the  resistance  of  a  cutting  edge 
with  a  spherical  surface,  while  an  elliptical  surface  had  but  half 
the  resistance  of  a  sphere. 

Center  of  Pressure.  Newton  assumed  that  when  a  rectangular 
plane  was  moved  through  the  air  at  an  angle  inclined  to  the  line  of 
motion,  the  center  of  pressure  and  the  center  of  surface  were  always 
coincident.  This  is  not  the  case,  however,  the  center  of  pressure 
varying  as  the  angle  of  incidence.  Numerous  experimenters  inves- 


Fig.  23.     Locus  of  Center  of  Pressure  for  Various 
Angles  of  Incidence  for  Curved  Plane 


140 


THEORY   OF   AVIATION 


43 


tigated  this  with  practically  similar  results,  Langley's  experiments 
with  his  "counterpoised  eccentric  plane"  having  been  of  this  nature. 
But  all  these  experiments  were  on  flat  surfaces  and  the  movement  of 
the  center  of  pressure  on  curved  surfaces  is  totally  different.  In 
deeply-arched  surfaces,  it  moves  steadily  forward  from  the  center 
of  surface  as  the  inclination  is  turned  down  from  90  degrees,  until 
a  certain  point  is  reached,  varying  with  the  depth  of  curvature, 
Fig.  23.  After  this  point  is  passed,  a  curious  phenomenon  takes 
place.  Instead  of  continuing  to  move  forward  with  a  decrease  of 


Fig.  24.      Six  Stages  of  Development  of  the  Aeroplane  Supporting  Surface 

angle,  the  center  of  pressure  turns  abruptly  and  moves  rapidly  to 
the  rear.  According  to  Wilbur  Wright,  this  action  is  due  largely  to 
the  pressure  of  the  wind  acting  also  on  the  upper  side  of  the  arched 
surface  at  low  angles.  The  action  is  unmistakable  and  has  often 
been  observed  in  practice;  the  reversal,  which,  according  to  Rateau, 
occurs  as  the  angle  of  15  degrees  is  approached,  strikingly  illustrates 
the  difference  in  the  conditions  of  pressure  on  a  curved  surface  at  low 
angles  as  compared  with  those  of  flat  surfaces.  A  region  of  instability 
at  30  degrees  also  appears  to  be  present  in  a  curved  surface. 

Evolution  of  Curved  Supporting  Surface.  The  foregoing 
emphasizes  the  great  importance  of  the  proper  curvature  of  the  sup- 
porting surfaces  of  an  aeroplane,  and  the  evolution  of  this  curve  has 


141 


44  THEORY   OF   AVIATION 

been  so  minute  and  apparently  so  insignificant  that  its  actual  impor- 
tance is  not  appreciated  except  by  the  experienced  designers  of 
machines.  Going  back  to  before  Lilienthal's  time,  it  may  be  said 
to  progress  in  six  stages,  Fig.  24 :  First,  the  flat  plane,  held  horizon- 
tally. Second,  at  an  angle  of  incidence.  (With  neither  of  these  was 
there  any  hold  on  the  air.)  Third,  the  true  arc  of  a  sphere  was 
emplbyed  and  with  this  curve  the  feat  of  lifting  a  man  in  gliding 
flight  was  first  accomplished,  due  primarily  to  the  fact  that  the  air 
was  not  thrown  off  at  such  a  sharp  angle  as  in  the  straight  plane. 
It  caused  the  air  to  compress  more  and  more  to  the  rear  of  the  curve, 
or  moved  the  center  of  pressure  backward.  Fourth,  the  next  step 
was  to  bend  the  forward  edge  of  the  arc  downward  sharply,  forming 
a  parabolic  curve  and  causing  the  air  to  shoot  upward  at  the  point 
of  contact,  giving  a  powerful  lift.  Fifth,  then  followed  the  remark- 
able discovery  that  with  a  certain  form,  the  upper  surface  of  the 
plane  exerts  as  much  lift  as  the  under  side.  This  was  obtained  by 
taking  a  flat  plane,  held  at  an  angle  of  incidence,  and  abruptly  bend- 
ing its  forward  edge  downward,  practically  at  right  angles.  By  this 
construction,  the  air  was  thrust  upward  on  the  outer  surface,  while 
the  air,  rushing  in  underneath  to  fill  the  partial  vacuum  thus  formed, 
exerted  a  powerful  lift  and,  at  the  same  time,  was  pushed  forward, 
thus  tending  to  diminish  the  head  resistance.  Still  more  important 
was  the  fact  that  the  air,  which  was  shot  vertically  upward  by  the 
butt  edge  of  the  curve,  tended  to  raise  the  plane  with  it,  giving  an 
upward  thrust  or  lift  almost  as  great  as  that  beneath  the  surface.  In 
the  final  stage,  the  plane  itself  is  no  longer  flat  but  curved  upward  as 
shown  in  the  figure.  In  Fig.  24,  these  curves  have  been  greatly 
exaggerated,  but  their  influence  will  be  apparent  upon  studying 
sections  of  the  supporting  planes  of  well-known  types  of  machines. 
The  reason  for  not  employing  such  exaggerated  curves  is  because 
of  the  excessive  head  resistance  that  would  be  created.  By  far  the 
greatest  factor  to  be  dealt  with  in  the  design  of  an  aeroplane  is  the 
resistance  to  motion.  On  its  elimination  as  far  as  possible  depend  the 
ability  to  fly,  the  speed,  and  the  power  efficiency.  The  total  resist- 
ance may  be  divided  into  three  parts :  First,  the  head  resistance  of 
the  framing  and  body;  second,  the  drift  of  the  plane  or  planes;  and 
third,  the  frictional  or  skin  resistance  of  the  whole.  To  fly,  this  com- 
bined resistance  must  be  overcome  by  the  thrust  of  the  propeller. 


142 


THEORY   OF   AVIATION  45 

INTERNAL  WORK  OF  THE  WIND 

Character  of  Air  Currents.  Before  the  researches  of  Langley 
showed  its  true  nature,  the  wind  was  commonly  assumed  to  be  a 
homogeneously  moving  body.  In  other  words,  where  not  influenced 
by  terrestrial  obstructions,  a  wind  blowing  at  a  certain  speed  rep- 
resented a  uniformly-moving  current  of  air,  at  any  point  in  the  body 
of  which  the  moving  air  would  be  found  to  have  the  same  speed 
and  the  same  direction  of  travel.  The  subject  is  one  of  great  impor- 
tance to  the  aviator,  and  a  knowledge  of  it,  in  outline  at  least,  is 
essential  to  an  understanding  of  many  things  that  otherwise  are 
inexplicable. 

Instead  of  being  a  homogeneously  moving  body,  Langley  found 
that  a  current  of  air,  even  where  movements  only  in  one  horizontal 
plane  are  considered,  is  always  filled  with  amazingly  complex  motions. 
Some  of  these,  if  not  in  opposition  to  the  main  movement,  are  rela- 
tively so — that  is,  are  slower,  while  others  are  faster  than  this  main 
movement,  so  that  there  is  always  a  portion  opposed  to  it.  These 
irregular  movements  of  the  wind,  which  take  place  up,  down,  and  on 
every  side,  are  accompanied  by  equally  complex  condensations  and 
expansions,  but  it  will  be  apparent  that  only  a  small  portion,  those 
occurring  in  a  narrow  current  whose  direction  is  horizontal  and 
sensibly  linear,  could  be  recorded  by  the  anemometer.  However 
complex  the  movement  may  appear  as  shown  by  the  records  of  the 
instrument,  it  is  then  far  less  so  than  the  reality. 

Movements  of  a  Plane  in  Wind.  With  Vertical  Guides.  We 
will  presently  examin&  the  means  of  utilizing  this  potentiality  of 
internal  work  in  order  to  cause  an  inert  body  wholly  unrestricted 
in  its  motion  and  wholly  immersed  in  the  current,  to  rise;  but  first 
let  us  consider  such  a  body  (a  plane)  whose  movement  is  restricted 
to  a  horizontal  direction,  but  which  is  free  to  move  between  fric- 
tionless,  vertical  guides.  Let  it  be  inclined  upward  at  a  small  angle 
(angle  of  incidence)  to  a  horizontal  wind,  so  that  only  the  vertical 
component  of  pressure  of  the  wind  on  the  plane  will  affect  its  motion. 
If  the  velocity  be  sufficient,  the  vertical  component  of  the  pressure 
will  equal  or  exceed  the  weight  of  the  plane,  and  in  the  latter  case, 
the  plane  will  rise  indefinitely. 

For  example,  if  the  plane  be  a  rectangle  whose  length  is  six 
times  its  width  with  an  area  of  2.3  square  feet  to  the  pound  and  an 


143 


46  THEORY   OF   AVIATION 

inclination  at  an  angle  of  7  degrees,  and  if  the  wind  have  a  velocity 
of  36  feet  per  second,  experiment  shows  that  the  upward  pressure  will 
exceed  the  weight  of  the  plane,  and  the  latter  will  rise  (if  between 
vertical,  nearly  frictionless  guides)  at  an  increasing  rate  until  it 
has  a  velocity  of  2.52  feet  per  second,  at  which  speed  the  weight 
and  upward  pressure  are  in  equilibrium.  (Langley,  "Experiments 
in  Aerodynamics.")  Hence,  there  are  no  unbalanced  forces  acting 
and  the  plane  will  have  attained  a  state  of  uniform  motion. 

For  a  wind  that  blows  during  10  seconds,  the  plane  will,  there- 
fore, rise  about  25  feet.     At  the  beginning  of  the  movement,  the 
inertia  of  the  plane  makes  the  rate  of  rise  less  than  the  uniform  rate, 
but  at  the  end  of  10  seconds,  the  inertia  will 
cause  the  plane  to    ascend   a   short   distance 
after  the  wind  has  ceased,  so  that  the  deficit 
at  the  beginning  will  be  counterbalanced  by 
the  excess  at  the  end  of  the  assigned  interval. 
Without  Vertical  Guides.     Such  a  plane  will 
be  lifted  and   sustained   momentarily,  even  if 
there  be  no  vertical  guides,  or,  in  the  case  of 
a  kite,  if  there  be  no  cord  to  sustain  it,  the  in- 
ertia of  the  body  supplying  for  a  brief  period, 
the  office  of  the  guides  or  cord.     If  suitably 
disposed,  it   will   commence   to   move    under 
rig.  25.    Movements  of      the  resistance  imposed  only  by  its  inertia  to 

a  Free  Plane  in  Air  ,        .  ,        .,  .          ,          ,.  .  PI 

a  horizontal  wind,  not  in  the  direction  of  the 

wind,  but  nearly  vertically.  As  the  plane  takes  up  more  and  more 
the  motion  of  the  wind,  this  inertia  is  overcome  and  the  lifting 
effect  decreases,  that  is,  if  the  wind  be  the  approximately  homo- 
geneous current  it  is  commonly  treated  as  being,  and  finally  the 
plane  falls.  If,  however,  a  counter-current  be  supposed  to  meet  this 
inclined  plane  before  its  inertia  is  exhausted  and  consequently  before 
it  ceases  to  rise,  it  is  only  necessary  to  assume  its  revolution  through 
180  degrees  about  a  vertical  axis,  to  see  that  it  will  be  lifted  still 
higher  without  any  other  call  for  expenditure  of  energy,  as  its  inertia 
now  reappears  as  an  active  factor.  Fig.  25  shows  what  might  be 
assumed  to  happen  to  a  model  inclined  plane  freely  suspended  in 
the  air,  and  endowed  with  the  power  of  rotating  about  a  vertical 
axis  so  as  to  change  the  aspect  of  its  constant  inclination,  which 


144 


THEORY   OF   AVIATION 


47 


need  involve  no  theoretical  expenditure  of  energy,  even  though  the 
plane  possess  inertia.  It  is  evident  that  the  plane  would  rise 
indefinitely  by  the  action  of  the  wind  in  alternate  directions.  The 
disposition  of  the  wind,  which  is  here  supposed  to  cause  the  plane  to 
rise,  appears  at  first  an  impossible  one,  but  it  becomes  virtually 
possible  by  a  method  which  we  will  now  point  out  and  which  leads 
to  a  practicable  one  which  we  may  actually  employ.  (It  must  be  borne 
in  mind  that  these  experiments  were  carried  out  in  1893 — ten  years 
before  the  first  flight  of  the  Wright 
Brothers.) 

Behavior  in  Pulsating  Wind.  Fig.  26 
shows  the  wind  blowing  in  one  constant 
direction,  but  alternately  at  two  widely- 
varying  velocities,  or  rather,  in  the  ex- 
treme case  supposed  in  the  illustration, 
where  one  of  the  velocities  is  negligibly 
small,  and  whose  successive  pulsations  in 
the  same  direction  are  separated  by  in- 
tervals of  calm.  A  frequent  alternation 
of  velocities,  united  with  constancy  of 
absolute  direction,  has  been  shown  to  be 
the  ordinary  condition  of  the  wind's 
motion;  but  attention  now  is  called  par- 
ticularly to  the  fact  that  while  these 
unequal  velocities  may  be  in  the  same 
direction  as  regard^  the  surface  of  the 
earth,  yet  as  regards  the  mean  motion  of  the  wind  they  are  in  oppo- 
site directions,  and  will  produce  on  a  plane,  whose  inertia  enables  it 
to  sustain  a  sensibly  uniform  motion  with  the  mean  velocity  of  this 
variable  wind,  the  same  lifting  effect  as  if  these  same  alternating 
winds  were  in  absolutely  opposed  directions,  provided  that  the 
constant  inclination  of  the  plane  alternates  in  its  aspect  to  corres- 
pond with  the  changes  in  the  wind. 

It  may  aid  in  clearness  of  conception,  if  we  assume  a  set  of  fixed 
co-ordinates,  X,  Y,  Z,  passing  through  0,  and  a  set  of  movable 
co-ordinates,  x,  y,  z,  moving  with  the  velocity  and  direction  of  the 
mean  wind.  If  the  moving  body  is  referred  to  the  first  only,  it  is  evi- 
dently subject  to  pulsations  which  take  place  in  the  same  directions 


Fig.  20.     Movements  of  a  Free 
Surface  in  a  Pulsating  Wind' 


145 


48  THEORY   OF   AVIATION 

on  the  axis  of  X,  but  it  must  also  be  evident  that  if  referred  to  the 
second,  or  movable  co-ordinates,  these  same  pulsations  are  in  opposite 
directions.  This,  then,  is  the  case  we  have  just  considered,  and  if 
we  suppose  the  plane  to  change  the  aspect  of  its  inclination  as  the 
direction  of  the  pulsations  changes,  it  is  evident  that  there  must  be 
a  gain  in  altitude  with  every  pulsation,  while  the  plane  advances 
horizontally  with  the  velocity  of  the  mean  wind. 

During  the  period  of  maximum  wind  velocity,  when  the  wind 
is  moving  faster  than  the  plane,  the  rear  edge  of  the  latter  must  be 
elevated.  During  the  period  of  minimum  velocity,  when  the  plane, 
owing  to  its  inertia,  is  moving  faster  than  the  wind,  the  front  edge 
of  the  plane  must  be  elevated.  Thus  the  vertical  component  of  the 
wind  pressure  as  it  strikes  the  oblique  plane  tends  in  both  cases  to 
give  it  a  vertical  upward  thrust.  So  long  as  this  thrust  is  in  excess 
of  the  weight  to  be  lifted,  the  plane  will  rise.  The  rate  of  rise  will 
be  greatest  at  the  beginning  of  each  period,  when  the  relative  velocity 
is  greatest  and  will  diminish  as  the  resistance  produces  "drift," 
i.e.,  diminishes  relative  velocity.  The  curved  line  OB,  Fig.  26, 
represents  a  typical  path  of  the  plane  under  these  conditions. 

It  follows  from  the  diagram,  Fig.  25,  that,  other  things  being 
equal,  the  more  frequent  the  wind's  pulsations,  the  greater  will  be 
the  rise  of  the  plane;  for  since  during  each  period  of  steady  wind 
the  rate  of  rise  diminishes,  the  more  rapid  the  pulsations,  the  nearer 
the  mean  rate  of  rise  will  be  to  the  initial  rate.  The  requisite  fre- 
quency of  pulsations  is  also  related  to  the  inertia  of  the  plane,  for 
the  less  the  inertia,  the  more  frequent  must  be  the  pulsations,  in 
order  that  the  plane  shall  not  lose  its  relative  velocity. 

Soaring.  It  is  obvious  that  there  is  a  limit  of  weight  which 
can  not  be  exceeded  if  the  body  is  to  be  sustained  by  any  such  fluctua- 
tions of  velocity  as  can  be  actually  experienced.  Above  this  limit 
of  weight  the  body  will  sink.  Below  this  limit,  the  lighter  the  body 
is,  the  higher  it  will  be  carried,  but  with  increasing  variability  of 
speed.  That  body,  then,  which  has  the  greatest  weight  per  unit  of 
surface  will  soar  with  the  greatest  steadiness,  if  it  soar  at  all,  not 
on  account  of  its  weight,  per  se,  but  because  the  weight  is  an  index 
of  its  inertia. 

The  student  who  will  compare  the  results  of  experiments  made 
with  any  artificial  flying  model,  like  those  of  Penaud,  with  the  weights 


146 


THEORY   OF   AVIATION  49 

of  the  soaring  birds,  as  given  in  the  tables  by  Mouillard,  or  other 
authentic  sources,  can  not  fail  to  be  struck  with  the  great  weight  in 
proportion  to  wing  surface  which  Nature  has  given  to  the  soaring 
birds,  compared  with  any  which  man  has  been  able  to  imitate  in 
his  models. 

This  great  weight  of  the  soaring  bird  in  proportion  to  its 
wing  area  has  been  again  and  again  noted,  and  that  without  weight 
the  bird  could  not  soar  has  been  frequently  remarked  by  writers 
who  felt  that  they  could  very  safely  make  such  a  paradoxical  state- 
ment in  view  of  the  evidence  nature  everywhere  gave  that  this 
weight  was  in  some  way  necessary  to  rising.  But  these  writers  have 
not  shown,  so  far  as  I  remember,  how  this  necessity  arises,  and  this 
is  what  I  now  endeavor  to  point  out. 

The  evidence  that  there  is  some  weight  which  the  action  of  the 
wind  is  sufficient  to  sustain  permanently  under  these  conditions  in  a 
free  body,  has  a  demonstrative  character.  It  is  obvious  that,  if  this 
weight  is  sustainable  at  any  height,  gravity  may  be  utilized  to  cause 
the  body  to  descend  on  an  inclined  course  to  some  distance.  This 
is  now  a  matter  of  such  common  experience  that  French  aviators 
term  it  volplane,  the  action  itself  already  having  been  anglicized  as 
" volplaning."  Seventeen  years  after  Langley  wrote  it,  Drexel  gave 
a  striking  example  of  its  truth  by  volplaning  from  a  height  of  more 
than  9,000  feet,  reaching  the  earth  at  a  point  15  miles  distant. 

We  have  already  seen  how  pulsations  of  sufficient  amplitude 
and  frequency,  of  the  kind  which  present  themselves  in  nature,  may, 
in  theory,  furnish  energy  sufficient  not  only  to  sustain  but  actually 
to  elevate  a  heavy  body  moving  in  and  with  the  wind  at  its  mean 
rate.  It  is  easy  now  to  pass  to  the  practical  case,  exemplified  by  the 
bird,  which,  soaring  on  rigid  wings,  but  having  power  to  change  its 
inclination,  uses  the  elevation  thus  gained  to  move  against  the  wind 
without  expending  any  sensible  amount  of  its  own  energy.  Here 
the  upward  motion  is  designedly  arrested  at  any  convenient  stage, 
i.e.,  at  each  alternate  pulsation  of  the  wind,  and  the  height  attained 
is  utilized  so  that  the  action  of  gravity  may  carry  the  body  by  its 
descent  in  a  curvilinear  path,  if  necessary,  against  the  wind. 

As  the  remainder  of  this  particular  study  of  Langley's  is  devoted 
to  demonstrating  the  practicability  of  the  theories  here  propounded, 
it  would  not  be  profitable  to  follow  them  any  further.  They  are 


147 


50  THEORY   OF   AVIATION 

now  a  matter  of  more  or  less  common  knowledge,  having  long  since 
been  raised  from  the  realm  of  theory.  But  the  influence  of  the 
"internal  work  of  the  wind,"  or  rather  its  "internal  character"  if  it 
may  be  so  termed  for  purposes  of  illustration,  upon  the  actual  opera- 
tion of  the  aeroplane,  is  of  the  greatest  importance,  and  moreover 
it  is  something  about  which  there  is  yet  a  great  deal  to  be  learned. 

Air  Holes.  The  deaths  of  Moissant  at  New  Orleans,  and  Hoxsey 
at  Los  Angeles,  on  December  31,  1910,  gave  rise  to  a  great  deal  of 
discussion  regarding  the  uncertain  character  of  the  atmosphere  as 
affected  by  the  wind,  and  emphasized  the  fact  that  very  little  is 
actually  known  concerning  it.  Both  being  experienced  aviators  of 
a  conservative  type,  it  was  difficult  to  account  for  the  accidents 
(nothing  apparently  having  gone  wrong  with  either  machine)  except 
on  the  ground  that  the  machine  had  suddenly  dropped  into  a  depres- 
sion in  the  atmosphere,  causing  it  "to  stand  on  its  head"  and  fall. 
The  latter  theory  is  supported  in  Hoxsey's  case  by  an  instantaneous 
photograph  of  his  machine  taken  at  the  moment  it  started  to  fall, 
and  showing  it  in  apparently  perfect  condition,  coming  down  in  a 
perfectly  vertical  line.  A  more  plausible  explanation,  however,  is 
that  Hoxsey,  having  just  descended  from  a  great  altitude  to  within 
500  feet  of  the  earth,  was  overcome  by  the  sudden  change  in  pressure 
(see  article  on  "Altitude"),  and  lost  consciousness.  In  so  doing, 
his  body  may  have  pitched  forward  against  the  lever  of  the  elevating 
rudder,  and  so  operated  the  latter  as  to  head  the  machine  vertically 
downward.  This  could  not  have  been  so  in  Moissant's  case  as  he 
had  not  been  up  more  than  a  hundred  feet,  the  accident  being  ascribed 
by  some  of  his  fellow  aviators  to  the  fact  that  he  attempted  to  land 
with  the  wind,  contrary  to  the  usual  custom. 

Whether  or  not  either  of  these  fatalities  was  due  to  these 
"pockets"  or  "holes"  in  the  air,  as  they  have  come  to  be  popularly 
termed,  will  never  be  known,  but  the  fact  that  the  atmosphere  (wind) 
instead  of  being  a  homogeneous  current  of  air,  the  character  of  which 
may  be  depended  upon,  is  a  complex  mass  of  points  of  high  and  low 
velocity,  or  none  at  all,  is  an  element  that  must  be  contended  with 
by  every  aviator.  Unlike  the  sailor,  he  can  not  see  an  unusual  wave 
coming,  nor  can  he  determine  deeps  and  shallows  by  the  appearance 
of  the  surface.  It  is  only  when  the  wave  or  gust  has  struck  the 
machine,  or  the  machine  itself  has  passed  into  one  of  the  pockets 


148 


THEORY   OF   AVIATION  51 

in  the  air,  that  the  aviator  knows  how  big  or  strong  it  is  going 
to  be,  or  how  far  the  sudden  fall  in  pressure  due  to  passing  over 
a  calm  spot  will  drop  the  machine.  One  of  the  troubles  of  aviators 
at  exhibition  meets  is  that  the  spectators  do  not  appreciate  the  dan- 
ger of  these  wind  waves  and  holes  and  so  expect  them  to  fly  in  weath  r 
that  is  really  dangerous,  although  it  may  appear  fine. 

Effect  of  Eddies  and  Waves.  On  an  open  plain  of  considerable 
extent,  such  as  that  at  which  the  aviation  meets  at  Rheims  are  held, 
there  is  nothing  to  interfere  with  the  wind  and  it  blows  more  steadily, 
though  as  Langley  has  pointed  out,  the  existence  of  swirls  and  eddies 
in  the  wind  is  independent  of  the  influence  of  obstructions.  It  is 
well  known,  however,  that  the  presence  of  obstructions  gives  it  a 
totally  different  and  far  more  dangerous  character.  Where  there 
are  hills,  banks,  and  trees  all  around,  the  wind,  even  when  blowing 
comparatively  gently,  comes  in  dangerous  waves,  swirls,  and  eddies, 
just  like  the  eddies  and  whirlpools  in  a  stream  that  has  rocks  or  other 
obstructions  to  impede  the  flow  of  the  water. 

To  properly  understand  the  effect  of  these  waves  and  eddies 
on  an  aeroplane,  the  theory  of  the  flight  of  the  latter  must  be  borne 
in  mind.  The  machine  is  sustained  in  the  air,  because  the  speed  at 
which  it  is  driven  produces  a  pressure  under  its  supporting  surfaces 
exceeding  its  total  weight;  hence,  the  pressure  lifts  it.  If  driven 
faster,  the  pressure  is  increased  and  its  sustaining  power  is  greater; 
if  driven  slower,  this  is  decreased  and  the  machine  tends  to  fall. 
In  fact,  we  have  the(  anomaly  of  prizes  being  offered  for  machines 
that  are  able  to  fly  slowly.  For  example,  if  a  machine  be  capable  of 
a  speed  of  40  miles  an  hour,  this  represents  a  close  approximation  of 
its  critical  speed — in  other  words,  it  must  fly  that  fast  or  not  at  all. 
By  speeding  up  the  motor,  it  may  be  able  to  fly  a  few  miles  an  hour 
faster,  but  it  can  not  fly  much  slower  and  still  sustain  itself  in  the  air 
—in  the  case  of  the  40-mile-an-hour  machine,  probably  not  much 
less  than  34  miles  an  hour. 

Owing  to  its  weight,  ranging  from  500  pounds  in  the  case  of  a 
small  monoplane,  up  to  almost  a  ton  for  some  of  the  largest  biplanes, 
the  inertia  due  to  the  high  speed  is  very  great,  and  the  machine  will 
accordingly  not  change  its  rate  of  travel  suddenly.  Therefore,  assume 
a  machine  flying  at  40  miles  per  hour  over  the  ground  in  a  gentle 
wind,  and  suppose  that  a  gust  traveling  10  miles  an  hour  faster  than 


149 


52  THEORY   OF   AVIATION 

the  wind,  against  which  it  has  been  going,  strikes  it.  The  machine 
can  not  slow  down  but  simply  charges  into  that  gust  at  40  miles  an 
hour.  Consequently,  the  pressure  on  the  wings  is  increased  and  the 
machine  rises  exactly  as  the  soaring  birds  do  under  similar  con- 
ditions. But  consider  the  effect  of  opposite  conditions.  Assume  the 
machine  to  have  reduced  its  speed  in  relation  to  the  earth,  so  as  to 
get  to  its  proper  flying  speed  in  relation  to  that  gust  of  wind.  Pres- 
ently, it  goes  right  through  that  gust  and  into  the  lull  on  the  other 
side,  just  as  a  boat  rides  over  a  wave  and  falls  into  the  trough  between 
the  waves.  Now  it  is  flying  too  slowly  for  the  area  of  comparative 
calm  that  follows  the  gust;  the  pressure  is  decreased  and  with  it  the 
lift,  so  that  the  machine  drops — if  not  very  high  it  may  strike  the 
ground,  as  has  often  been  the  case.  If  high,  it  merely  drops  until 
it  picks  up  its  normal  speed  again  and  increases  the  pressure  accord- 
ingly. The  sudden  drop  is  very  disconcerting  and  is  the  cause  of 
numerous  accidents,  particularly  where  the  machine  is  not  up  high 
enough  to  permit  of  falling  into  one  of  these  "holes  in  the  wind" 
without  coming  to  earth. 

Relative  Speed  of  Wind  and  Aeroplane.  The  speed  of  a  machine 
through  the  air  has  little  to  do  with  its  speed  over  the  ground.  The 
important  thing  is  its  speed  with  relation  to  the  wind  against  which  it 
is  traveling — or  rather  attempting  to  travel  would  be  better,  as 
strikingly  illustrated  by  the  experience  of  Johnstone  and  Hoxsey 
trying  to  make  headway  against  a  gale  of  wind  at  the  International 
Meet  at  Belmont  Park.  The  wind  was  blowing  40  to  50  miles  an 
hour,  exceeding  the  speed  of  which  the  Wright  biplanes  were  capable. 
They  accordingly  simply  headed  directly  into  the  wind  and  were 
blown  backward  by  it,  at  times  remaining  perfectly  motionless  in 
the  air,  with  regard  to  the  ground,  when  the  wind  and  the  thrust 
of  the  propellers  equalized  each  other,  gaining  a  little  at  each  lull, 
and  losing  more  with  each  stronger  gust,  Johnstone  traveling  more 
than  40  miles  in  this  manner,  while  Hoxsey  went  about  two-thirds 
of  that  distance  before  alighting.  Hence,  it  is  easy  to  appreciate 
that  the  40-mile-an-hour  machine,  which  can  make  that  speed  in 
still  air,  can  travel  only  20  miles  an  hour  against  a  20-mile  wind, 
and  can  travel  60  miles  an  hour  over  the  ground  with  a  20-mile  wind. 

Assume  the  machine  to  be  flying  in  a  gusty  wind;  it  is  making 
40  miles  an  hour  and  is  in  a  gust  traveling  20  miles  an  hour.  The 


150 


THEORY   OF   AVIATION  53 

biplane  is  going  60  miles  an  hour  and  will  accordingly  travel  through 
the  gust  in  a  short  ,time  into  slower  air,  traveling  at,  say,  10  miles 
an  hour.  The  machine  is  then  going  60  and  the  wind  only  10  miles, 
so  the  machine  is  going  50  miles  an  hour  faster  than  the  air  when  it 
should  be  going  only  40.  Consequently,  the  pressure  under  the  planes 
increases;  the  machine  rises  suddenly  till  the  rush  of  the  extra 
momentum  is  expended ;  and  then  settles  down  to  its  proper  speed  of 
40  miles  an  hour  through  the  wind,  plus  the  10-mile-wind  speed, 
which  makes  50  miles  an  hour. 

Then  the  machine  runs  through  the  slow  wind  and  overtakes 
another  patch  traveling  at,  say,  20  miles  an  hour.  This  time  the 
machine  is  doing  50  miles  an  hour,  and  only  30  an  hour  more  than 
the  wind,  which  is  not  enough  to  keep  it  in  the  air,  so  the  whole 
machine  falls  until  the  thrust  of  the  propellers  has  given  it  sufficient 
speed  to  pick  up  the  extra  10  miles  an  hour  required  to  attain  its 
critical  speed  of  40  miles  an  hour,  and  by  that  time  it  will  be  going 
60  miles  an  hour  over  the  ground  again. 

Certain  Effects  on  the  Wind.  Another  important  thing  to 
understand  is  the  effect  of  different  obstructions  on  the  wind.  A 
wind  blowing  against  a  hillside  is  bound  to  blow  up  along  its  sides 
and  the  wind  next  to  the  ground  will  be  compressed  by  the  other 
wind  meeting  it,  so  that  when  it  gets  to  the  top  of  the  hill  it  will 
expand,  and  some  of  it  will  blow  level  along  the  top  of  the  hill  and 
some  of  it  will  continue  to  rise.  An  aeroplane  falling  off  the  top  of 
such  a  hill — the  bo^v  of  a  war  vessel,  as  an  example— would  be  lifted 
quite  easily.  Again,  when  a  wind  strikes  a  cliff  face,  the  compression 
may  be  so  great  that  the  wind  will  rise  straight  up  and  curl  over, 
just  like  a  wave,  while -close  to  the  edge  there  might  be  no  wind  at  all. 
An  aeroplane  flying  in  such  a  wind  might  well  be  caught  in  the 
"curlover,"  and  dashed  to  the  ground;  but  if.it  got  as  far  as  the  edge, 
it  would  be  lifted  by  the  up-draft. 

Downward  drafts  also  occur  and  these  are  dangerous  to  aero- 
planes, because  if  the  pressure  suddenly  comes  from  above,  as  in 
flying  into  such  a  wind,  it  is  difficult  to  increase  the  speed  quickly 
enough  to  counteract  this  by  generating  sufficient  pressure  beneath 
the  planes.  Only  high  speed  and  a  powerful  motor  would  make  it 
possible.  The  commonest  kind  of  down-draft  is  formed  when  the 
wind  blowing  over  the  top  of  a  hill  finds  the  air  in  the  valley  at  a 


151 


54  THEORY   OF   AVIATION 

lower  pressure,  and  consequently,  due  to  the  pressure  behind  it, 
swoops  down  into  the  valley.  Curtiss  experienced  numerous  down- 
drafts  of  this  kind  in  his  flight  from  Albany  to  New  York  down  the 
Hudson  River  valley.  A  less  common  kind  of  wind  is  met  with  when 
a  cold  wind  over  the  sea  descends  to  a  cliff  edge  to  replace  air  that  is 
being  drawn  away  to  fill  the  place  of  hot  air  ascending  from  the 
heated  earth  farther  inland.  This  is  the  phenomenon  that  causes 
sea  breezes  and  land  breezes  alternately  at  different  times  of  the  day. 
This  uncertain  character  of  the  atmosphere — the  sudden  and 
extreme  variations  in  the  speed  of  the  wind,  and  frequently  in  its 
direction  as  well,  is  something  for  which  the  aviator  has  to  be  con- 
stantly on  the  alert.  It  is  one  of  the  chief  reasons  why  it  is  safer  to 
fly  at  a  height  than  comparatively  near  the  ground,  for  then,  unless 
the  aviator  has  been  entirely  demoralized  by  the  sudden  drop,  there 
is  time  for  him  to  regain  control  of  the  machine  before  striking  the 
earth. 


152 


THEORY  OF  AVIATION 

PART  II 


GLIDING  AND  SOARING 
GLIDING   FLIGHT 

If  it  were  rumored  that  Edison  was  conducting  secret  experi- 
ments with  a  view  to  making  a  new  type  of  electric  generator  out 
of  a  block  of  wood,  there  would  doubtless  be  columns  about  it  in  the 
daily  papers  and  much  of  what  was  written  would  be  regarded  by 
many  as  having  a  basis  of  fact,  if  not  the  whole  truth  of  the  matter. 
Exactly  the  same  thing  happens  when  the  Wright  Brothers  set  out 
to  conduct  experiments,  the  press  reports  of  the  gliding  flights  made 
at  Kitty  Hawk,  North  Carolina,  in  the  fall  of  1911,  forming  an 
aggravated  instance  of  this  kind.  The  tenor  of  practically  all  the 
reports  was  to  the  effect  that  the  Wright  Brothers  were  seriously 
engaged  in  trying  to  perfect  a  machine  that  would  fly  without  power, 
and  a  wealth  of  detail  accompanied  the  description  of  its  success  in 
accomplishing  this.  Some  went  so  far  as  to  state  that  the  new  Wright 
machine  was  of  the  wing-flapping  order  and  that  the  solution  of  the 
problem  of  flight  without  power  was  already  as  good  as  achieved, 
as  the  machine  was  Capable  of  hovering  indefinitely  over  a  selected 
spot — also  that  it  was  capable  of  imitating  the  soaring  flight  of  the 
larger  birds.  The  customary  reticence  of  the  inventors  themselves 
was,  of  course,  regarded  as  further  evidence  of  mysterious  and 
marvelous  achievements  of  too  great  import  to  be  talked  about 
publicly.  Undoubtedly,  this  attitude  on  the  part  of  the  press  and 
public  has  been  inspired  largely  by  the  vague  idea  that  soaring  flight 
pure  and  simple  is  an  impending  development  in  this  field  of  engineer- 
ing. In  other  words,  that  the  time  is  close  at  hand  when  man  can 
finally  claim  to  have  succeeded  in  endowing  himself  with  the  power 
of  the  birds.  To  those  who  have  given  the  subject  any  serious 
thought  or  study,  the  utter  fallacy  of  such  claims  will  be  apparent, 
and  the  Wright  Brothers  themselves  would  undoubtedly  be  the  last 

Copyright,  1912,  by  American  School  of  Correspondence. 


153 


56  THEORY   OF   AVIATION 

to  even  intimate  it.  As  at  present  constituted,  human  life  is  possible 
only  within  a  comparatively  short  distance  of  the  earth,  as  restricted 
by  the  necessary  density  of  the  atmosphere,  and  as  long  as  man  stays 
in  that  atmosphere  he  is  subject  to  the  influence  of  gravity.  To 
overcome  that  influence,  power  is  indispensable,  and  in  the  case  of 
the  gliding  aeroplane,  this  may  take  two  forms,  viz,  the  force  of  the 
wind,  and  the  impulse  that  may  be  obtained  by  taking  advantage  of 
gravity  itself. 

The  sight  of  a  glider  actually  advancing  into  a  50-mile  wind, 
hovering  stationary  (with  reference  to  the  earth)  over  one  spot  for 
ten  minutes  and  making  a  short,  circular  flight  which  began  and 
ended  at  the  same  spot,  might  well  give  rise  to  such  stories  of  the 
advent  of  the  aeroplane  without  a  motor  as  appeared  at  the  time, 
but,  as  a  matter  of  fact,  the  chief  object  of  the  Wrights  was  to  test 
the  stability  of  a  new  type  of  tailless  machine  and  at  the  same  time 
to  carry  further  the  exhaustive  experiments  in  free  flight  which  were 
made  for  such  a  lengthy  period  prior  to  the  actual  building  of  the 
first  power  machine. 

New  Wright  Glider.  The  new  glider  is  a  characteristic  Wright 
biplane  type  with  a  span  of  32  feet  and  a  chord  of  5J  feet,  having  a 
total  weight  of  about  145  pounds.  The  wings  appear  to  be  identical 
with  those  'of  the  standard  Wright  power-driven  machines  and  are 
correspondingly  thin  and  flat  in  curvature,  though  it  may  be  quite 
possible  that  the  supporting  surfaces  themselves  were  also  made  the 
subject  of  tests.  The  two  surfaces  are  separated  by  eight  pairs  of 
vertical  struts  of  the  same  form  as  those  ordinarily  employed  in 
Wright  construction.  They  space  off  the  total  span  into  seven 
sections  and,  as  formerly,  the  central  span  is  made  narrower  than 
the  others,  while  for  convenience  in  shipping  it  is  made  separable 
from  the  others.  The  operator  is  seated  directly  in  the  center  of  the 
machine  on  the  forward  edge  of  the  lower  plane.  The  center  section 
and  the  two  sections  on  either  side  of  it  are  rigidly  trussed  in  all 
directions  by  diagonal  bracing  wires,  leaving  the  first  two  sections 
from  each  wing  tip  free  to  undergo  the  distortion  involved  in  warp- 
ing. The  wings  are  warped  and  the  double  vertical  rudder  is  operated 
by  a  single  lever  with  a  jointed  head,  placed  at  the  right  of  the  aviator, 
while  the  elevator  is  worked  by  a  lever  at  the  left.  Both  the  vertical 
and  horizontal  tail  surfaces  are  carried  on  a  light  skeleton  box  girder 


154 


THEORY  OF  AVIATION  57 

similar  to  that  employed  on  the  power  machine.  In  fact,  the  new 
glider  does  not  differ  materially  from  the  Model  "B"  Wright  machine, 
except  for  the  single  vertical  fin,  about  a  foot  wide,  which  extends 
the  entire  height  of  the  space  between  the  main  planes  and  is  placed 
just  in  front  of  them  to  the  left  of  the  aviator,  this  being  simply  a 
substitute  for  the  fin-like  stabilizing  surfaces  employed  on  all  except 
the  original  type  of  Wright  machine  which  had  the  elevator  some 
distance  forward  of  the  main  planes.  The  runners  are  similar  in 
construction  but  have  been  made  so  low  as  to  barely  keep  the  lower 
main  plane  off  the  ground,  this  presumably  having  been  done  to 
reduce  the  head  resistance  to  a  minimum.  To  secure  accurate  longi- 
tudinal balance  of  this  experimental  glider,  an  outrigger  or  single 
stick  extending  forward  was  employed.  Attached  to  this  was  weight 
which  could  be  conveniently  varied  in  quantity  or  shifted  in  position 
to  give  greater  or  less  leverage. 

Gliding  Flights  at  Kitty  Hawk.  While  the  results  achieved 
with  this  new  glider  have  been  of  a  startling  nature,  a  little  study 
indicates  that  they  differ  only  in  duration  and  in  the  greater  skill  in 
maneuvering  developed  by  several  years  of  actual  flying,  from  those 
carried  out  in  1903  on  the  same  spot.  The  Wright  Brothers  have 
succeeded  in  making  glides  that  far  exceed  anything  done  in  this 
line  before,  in  attaining  greater  heights  and  greater  distances,  and 
in  staying  aloft  for  a  longer  time,  but  that  most  of  this  must  be 
attributed  to  the  great  skill  they  have  acquired  in  the  eight  years 
constant  flying  of  th^ir  power  machines  that  have  elapsed  since  the 
former  gliding  experiments  were  made,  rather  than  to  any  radical 
innovations  in  the  machine  itself  must  be  apparent.  Eight  years 
ago,  the  number  of  really  expert  gliders  to  be  found  among  the  entire 
body  of  experimenters  could  probably  have  been  counted  on  the 
fingers  of  one  hand,  and,  of  this  small  number,  the  Wrights  would  nat- 
urally head  the  list,  having  been  the  only  investigators  after  Lilienthal 
to  carry  out  a  consistent  series  of  experiments  of  this  kind  to  their 
logical  conclusion.  The  majority  of  investigators  were  bent  upon 
taking  what  appeared  to  be  a  direct  short  cut  by  immediately  build- 
ing a  power  machine,  which  neither  they  nor  anyone  else  knew  how 
to  fly,  even  if  it  were  capable  of  such  a  feat,  and  many  others  are 
wasting  time  and  effort  in  the  same  misguided  manner  today. 

The  skill  that  the  Wright  Brothers  have  since  developed  in  the 


155 


58  THEORY   OF   AVIATION 

control  of  their  power  machines  was  strikingly  apparent  in  the 
handling  of  the  new  glider.  With  consummate  ease,  Orville  Wright 
glided  off  the  top  of  the  hill  against  a  50-mile  gale,  and  succeeded 
in  not  only  soaring  over  one  spot  for  a  period  of  ten  minutes,  but  in 
actually  advancing  against  the  wind.  This  great  flight  was  made 
over  the  side  of  the  hill  facing  the  wind  so  that  the  air  currents  must 
have  had  a  decidedly  upward  trend.  The  distance  covered  was  a 
quarter  of  a  mile  and  the  height  attained  was  estimated  at  200  feet 
above  the  ground.  At  times,  the  machine  would  rise  or  fall  without 
horizontal  displacement,  and  then  again  it  would  glide  ahead  or 
drift  back,  as  fluctuations  in  the  wind  facilitated  these  maneuvers. 
At  all  times,  it  exhibited  the  positiveness  and  certainty  of  control 
for  steering,  balancing,  and  landing  that  is  characteristic  of  a  power 
machine.  But  that  even  these  features  of  the  performance  are 
neither  novel  nor  new,  except  in  the  degree  of  their  accomplish- 
ment, is  attested  by  the  Wright  Brothers'  own  reports  of  their 
first  gliding  experiments  communicated  to  the  Smithsonian  Institu- 
tion and  to  the  Western  Society  of  Engineers,  in  which  mention  is 
made  of  brief  hovering,  gain  of  altitude,  and  advancing  against  the 
wind  by  taking  advantage  of  winds  blowing  up  a  slope.  The  action 
of  a  wind  blowing  up  a  slope  or  meeting  an  obstruction  is  explained 
under  "Internal  Work  of  the  Wind." 

Glider  Sustained  without  Apparent  Motion.  Popular  miscon- 
ception has  naturally  centered  about  the  ability  of  the  machine  to 
hover  over  a  certain  spot,  while  the  fact  of  being  able  to  actually 
advance  against  a  50-mile-an-hour  wind  has  been  made  the  basis  of 
the  tales  regarding  the  motorless  aeroplane  of  the  near  future.  It  is 
a  matter  of  common  knowledge  that  to  secure  sustentation,  the  aero- 
plane must  be  in  continuous  forward  movement,  but  what  appears 
not  to  be  so  well  known  is  the  fact  that  this  movement  requires  to 
be  only  through  the  air,  as  explained  in  "Building  and  Flying  an 
Aeroplane,"  and  sustains  only  a  most  incidental  relation  to  the 
ground.  It  follows  that  if  the  whole  body  of  the  air  is  moving  in  the 
form  of  a  wind  across  the  earth's  surface  at  a  speed  of  50  miles  an 
hour,  an  aeroplane  will  be  normally  sustained  by  it  without  making 
any  progress  whatever  with  reference  to  the  ground.  Relatively 
to  the  air,  it  is  the  same  as  if  a  power  machine  were  being  driven  at 
50  miles  an  hour  in  a  perfect  calm.  Conversely,  if  the  aeroplane 


156 


THEORY   OF   AVIATION  59 

travel  with  the  wind,  it  must  fly  at  its  normal  speed  or  greater  owing 
to  the  following  wind,  and  to  this  there  will  be  added  the  wind's  speed, 
so  that  it  will  be  traveling  over  the  ground  at  a  rate  in  excess  of  100 
miles  an  hour.  This  actually  happened  to  Lieutenant  Conneau  in 
the  Paris-Madrid  race.  Of  course,  the  extreme  conditions  of  a 
complete  doubling  or  nullification  by  the  wind  of  an  aeroplane's 
speed  are  unusual,  but  less  extreme  conditions  involving  the  same 
principle  are  common  to  all  aeroplane  flights  not  undertaken  in  a 
dead  calm,  and  in  which  there  are  all  degrees  of  minor  additions  to 
or  subtractions  from  the  actual  speed  of  the  machine  by  the  effect 
of  the  wind. 

Where  the  rising  and  advancing  are  concerned,  it  is  due  partly 
to  the  peculiar  phenomena  often  called  "Lilienthal's  tangential"  that 
a  glider  with  cambered  planes  can  not  only  remain  stationary,  but 
in  a  wind  of  great  enough  upward  trend  can  be  made  to  actually 
advance  by  taking  advantage  of  the  motive  power  of  the  wind  itself 
that  is  blowing  against  the  glider.  This  may  appear  to  border  on 
the  miraculous  and  to  savor  strongly  of  perpetual  motion,  but  it 
must  be  borne  in  mind  that  the  huge  energy  of  the  rising  current  itself 
is  the  source  of  power.  The  phenomenon  referred  to  is  merely  that 
at  certain  angles  the  total  air  pressure  acting  on  a  plane  ceases  to 
act  in  a  line  normal  to  the  plane  or  its  chord,  and  instead  the  line 
of  action  of  this  force  takes  a  position  well  in  front  of  the  normal, 
the  pressure  thus  materially  acting  in  the  dual  role  of  a  supporting 
and  propelling  force.  /Octave  Chanute,  as  early  as  1909,  pointed  out 
in  a  masterly  way  the  manner  in  which  this  problem  of  soaring  could 
be  solved  and  many  experts  who  have  since  investigated  the  subject 
are  convinced  that  it  is  a  feasible  one. 

Lift  and  Drift  Ratio.  Another  point  that  may  be  made  clear  in 
this  connection  is  the  fact  that  any  wing  surface,  at  a  fixed  angle 
and  with  a  constant  loading,  has  a  certain  critical  speed  at  which  it 
is  normal  for  it  to  travel  and  at  which  the  resistances  it  opposes  to 
movement  through  the  air  are  a  certain  fixed  percentage  of  its  weight 
—the  "lift  to  drift  ratio"  referred  to  under  "Aerodynamics."  To 
overcome  the  drift  resistance,  it  is  necessary  to  produce  either  pro- 
peller thrust  of  corresponding  magnitude  or  to  resolve  the  weight  of 
the  machine  itself  into  a  propelling  component  by  coasting  it  down- 
hill on  the  air,  so  to^speak.  It  will  be  evident  from  this  that  the 


157 


60  THEORY    OF    AVIATION 

Wrights'  experiments  also  may  have  had  this  important  investiga- 
tion as  one  of  their  objects,  viz,  the  improvement  of  the  lift  to  drift 
ratio — in  a  glider,  by  flattening  the  angle  of  coasting  necessary  to 
sustain  it  aloft,  and  in  a  power  machine,  by  reducing  the  amount  of 
propeller  thrust  and  consequently  the  size  of  the  motor  required. 
A  less  apparent  but  none  the  less  real  advantage  of  flattening  the 
gliding  angle  inheres  in  the  possibility  it  opens  up  of  taking  extensive 
advantage  of  rising  currents  in  the  atmosphere  as  a  means  of  assist- 
ing in  the  propulsion  of  aeroplanes ;  for  such  currents,  while  common, 
are  not  ordinarily  of  sufficient  magnitude  to  sustain  machines  of 
such  excessively  abrupt  gliding  angles  as  are  now  universal.  In  thus 
taking  advantage  of  rising  currents,  in  much  the  same  manner  that 
is  probably  employed  by  the  large  soaring  birds,  the  chief  essential 
must  always  be  a  gliding  angle  so  flat  that  the  machine  loses  alti- 
tude slower  than  the  air  rises,  thus  continuing  indefinitely  to 
coast  down  an  invisible  hill  that  rises  faster  than  the  machine  slides 
down  it. 

It  was  also  generally  reported  that  one  of  the  chief  objects  of 
the  Wright  Brothers'  experiments  was  to  test  out  an  entirely  new 
system  of  automatic  balancing.  As  a  matter  of  fact,  they  had  actually 
intended  to  test  the  pneumatic  devices  patented  in  1909  and  described 
in  " Automatic  Stability,"  but  the  experiments  were  confined  to 
gliding  flights  with  the  usual  warping  control  to  preserve  lateral 
balance.  During  the  course  of  these  flights,  a  curious  accident 
happened.  After  rising  from  the  side  of  the  hill  about  20  feet,  the 
heavy  rear  rudder  appeared  to  become  uncontrollable  and  to  make 
the  glider  so  "tail  heavy"  that  it  began  to  turn  over  and  start  back- 
ward, whereupon  Wright  climbed  to  an  upright  position  of  safety 
on  the  overturning  machine  with  such  excellent  judgment  that, 
when  it  struck  the  ground  and  smashed,  he  emerged  unhurt.  This 
experience  suggests  that  it  is  a  mistake  to  strap  the  aviator  to  his 
seat  as  is  done  in  many  of  the  monoplanes,  and  that  frequently 
accidental  injury  might  be  avoided  by  a  good  use  of  similar  cool- 
headedness  in  time  of  danger.  Though  the  results  attained  are 
astonishing  to  many,  those  familiar  with  the  nature  of  air  currents 
expect  even  more  startling  performances  at  an  altitude  three  to  four 
times  as  great,  as  demonstrated  by  the  experiments  of  Professor 
John  J.  Montgomery  in  California  several  years  ago. 


158 


THEORY    OF    AVIATION  61 

Montgomery's  Gliding  Experiments.  Professor  Montgomery 
was  one  of  the  pioneer  investigators  in  the  gliding  field,  his  first 
experiments  having  been  made  from  1883  to  1886,  when  he  built 
three  machines  of  the  flapping  wing  order — needless  to  add,  without 
much  success.  Then  he  constructed  a  glider  with  its  supporting 
surfaces  modeled  after  the  gull's  wing,  following  nature  blindly, 
as  the  reason  for  the  downward  curving  surface  of  the  attacking 
edge  of  the  wing  was  not  understood.  This  machine  had  a  spread 
of  20  feet  and  a  depth  of  4|  feet,  thus  forming  a  close  approximation 
to  the  aspect  ratio  that  has  since  been  determined  as  the  most  efficient 
for  a  glider.  Success  attended  the  experiments  with  it  from  the  start, 
the  first  trial  resulting  in  a  glide  of  600  feet;  subsequently  a  great 
many  experimental  glides  were  made  with  it  until  its  short- 
comings made  further  trials  risky.  Though  this  first  Montgomery 
glider  was  a  success  in  one  respect,  it  was.  defective  in  equilibrium, 
and  its  maker  again  resorted  to  nature  for  the  solution  of  the  prob- 
lem. Close  observations  of  vultures  were  made  and  the  character- 
istic twisting  of  the  wings  in  soaring  flight  was  noted.  A  second 
glider  was  accordingly  built  in  1885,  but  while  the  principle  of 
equilibrium  as  found  in  the  bird's  wing  was  followed,  the  form  of 
surface  was  departed  from  as  it  seemed  unreasonable  that  the  wing 
should  be  inclined  downward  at  the  front.  The  second  machine  was 
accordingly  made  with  flat  surfaces.  It  was  somewhat  larger  than 
the  first  and  to  afford  lateral  stability,  each  wing  was  hinged  diag- 
onally. This  diagonal  hinge  allowed  the  "flaps"  thus  formed  to  yield 
to  undue  pressure  on  Cither  side.  These  flaps  were  held  in  a  normal 
position  by  springs.  If  the  wind  pressure  became  excessive,  the 
flap  of  that  wing  would  yield  a  little.  In  addition  to  the  springs, 
the  saddle  was  constructed  with  an  upright  to  which  wires  running 
to  the  rear  portions  of  the  wings  were  attached,  so  that  the  oper- 
ator could  lean  to  one  side  or  the  other,  giving  a  greater  depth  of 
curvature  to  one  wing  than  to  the  other,  but  not  giving  different 
angles  of  incidence  to  the  wings  as  the  Wrights  do.  Ader's 
"gauchissement"  (twisting),  for  which  the  French  claimed  so 
much,  was  the  same  effect;  so  that  neither  was  an  anticipation 
of  the  principle  of  warping  as  effected  by  the  Wright  Brothers, 
though  many  claims  of  this  have  been  made  for  them.*  The 

*It  is  significant  that  none  of  these  claims  was  put  forth  until  about  1907-1908,  when 
the  details  of  the  Wright  invention  had  become  generally  known. — ED. 


159 


62  THEORY  OF  AVIATION 

control  of  this  machine  proved  excellent  but  its  gliding  ability  was 
far  inferior  to  the  first,  so  that  the  curved  wing  surface  was  again 
returned  to  in  the  building  of  the  third  glider,  with  the  exception, 
however,  that  its  maker  could  not  bring  himself  to  believe  that  the 
downward  curving  surface  in  front  was  correct,  so  that  a  compromise 
was  made  by  turning  the  front  edge  up  a  little,  the  remainder  of  the 
wing  being  similar  to  that  of  a  vulture.  The  two  wings  were  placed 
at  a  dihedral  angle.  In  this  glider,  the  warping  principle  was  carried 
out  in  a  different  way.  A  lateral  beam  was  placed  along  the  front 
of  each  wing,  and  these  two  wings  were  capable  of  being  rotated  in 
a  socket  in  the  frame  extending  backward  to  the  tail.  Wires  from 
the  rear  of  each  wing  ran  to  levers — one  for  each  wing — placed  at  the 
right  and  left  hands  of  the  operator,  who  sat  on  a  saddle  as  in  the 
previous  gliders.  With  the  aid  of  these  levers,  either  one  or  both 
of  the  wing  tips  could  be  depressed,  placing  the  machine  under 
perfect  control  regardless  of  whether  the  wind  was  regular  or  gusty, 
the  angle  of  the  wings  being  changed  to  meet  varying  conditions. 
This  glider  had  an  even  larger  surface  than  the  second  one,  but  was 
inferior  in  lifting  power  even  to  the  first  glider  with  its  true  wing 
surface.  Professor  Montgomery  then  concluded  that  he  had  not 
succeeded  in  attaining  the  proper  form  of  surface,  and  further  that 
little  or  nothing  was  known  of  aerodynamics.  As  a  matter  of  fact, 
there  was  practically  no  data  of  any  value  extant  at  that  time,  so 
that  a  search  of  existing  records  did  not  bring  anything  worth  while 
to  light.  The  machine  was  accordingly  dismantled  and  a  study  of 
the  problem  undertaken  from  the  beginning,  to  ascertain,  if  possible, 
the  laws  of  aerodynamics  determining  the  proper  form  of  surface 
to  give  such  phenomena  as  the  soaring  of  birds.  In  1886,  Professor 
Montgomery  constructed  a  whirling  table  consisting  of  a  couple 
of  rails  fastened  together  and  mounted  on  a  pivot.  Surfaces  of 
various  forms  were  fastened  to  the  ends  of  this  and  the  table  whirled 
rapidly  to  study  their  movements.  Right  from  the  start,  a  peculiar 
phenomenon  was  noticed,  suggesting  that  something  was  taking 
place  in  advance  of  the  surfaces,  and  in  order  to  test  this,  thistle- 
down was  scattered  so  as  to  determine  the  direction  of  the  wind. 
Having  learned  this,  a  large  barn  door  was  set  on  the  ground  at  an 
angle  of  about  ten  degrees  and  a  reaction  of  the  wind  in  front  of  it 
was  immediately  noticeable.  Instead  of  the  wind  coming  in  a  straight 


160 


THEORY   OF   AVIATION  (33 

line,  it  traveled  in  a  gradual  curve  and  rose  to  strike  the  surface, 
indicating  that  the  surface  had  an  action  on  the  wind  in  front  of  it, 
making  plain  the  reason  for  the  curving  surface  of  a  bird's  wing. 

Professor  Montgomery  resumed  his  investigations  in  1903 
and,  having  discovered  the  fundamental  principles,  was  enabled  to 
put  them  into  practice  in  the  machines  he  built.  These  were  designed 
strictly  along  scientific  lines  and  were  tested  in  various  ways.  A 
cable  was  stretched  across  a  150-foot  valley,  and  by  means  of  cord, 
different  models  were  liberated  from  that  height  in  every  possible 
way,  head  down,  tail  down,  and  upside  down.  In  every 
case,  they  would  glide  safely  to  the  ground,  regardless  of  the  manner 
in  which  they  had  been  liberated.  In  all  of  these  models,  the  warp- 
ing idea,  developed  in  1885  and  1886,  was  employed,  and  having 
found  that  they  were  perfect  in  equilibrium  and  control,  large  machines 
patterned  exactly  after  the  models  were  built.  To  test  these  they 
were  elevated  on  a  cable  between  poles  and  were  dropped  alone 
and  with  weights.  They  were  then  tried  in  actual  gliding  flights, 
and  it  was  unexpectedly  discovered  that  they  would  respond  very 
rapidly  to  a  change  in  the  wind.  The  hill  employed  as  the  scene  of 
the  flight,  had  a  canon  across  the  bottom  of  it  and  it  was  found  that 
while  the  wind  blew  directly  in  the  glider's  face  as  he  started  down, 
it  was  blowing  along  the  canon  at  right  angles,  and  as  soon  as  the 
machine  came  under  its  influence  it  was  whirled  rapidly  to  the  right, 
but  was  not  upset.  For  the  purpose  of  developing  the  machine  further, 
and  at  the  same  tipie  of  exhibiting  it,  the  services  of  a  parachute 
jumper  with  a  hot-air  balloon  were  secured.  Professor  Montgomery's 
idea  was  to  commence  experimenting  by  raising  a  man  a  short  dis- 
tance in  the  air  and  dropping  him,  but  the  parachute  jumper  insisted 
on  going  up  at  least  a  thousand  feet  for  the  first  trial.  The  machine 
was  accordingly  so  adjusted  that  it  was  impossible  for  him  to  get 
control  of  it  and  thus  make  a  mistake  and  fall,  clamps  controlling 
the  tail  and  wings  giving  a  certain  limited  action,  however.  The 
first  trial  resulted  in  a  beautiful  glide,  and  then  more  liberty  of  action 
was  allowed  in  the  adjustments,  and  the  hot-air  balloon  carried  the 
glider  to  a  height  of  three  thousand  feet.  The  instructions  to  the 
operator  were  to  return  to  the  starting  point,  but  as  he  cut  loose 
from  the  balloon,  he  lost  his  direction  and  started  to  fly  in  the  opposite 
direction,  but  after  a  few  minutes  realized  his  mistake  and  made  a 


161 


64  THEORY   OF   AVIATION 

fine  sweep,  passing  through  two  or  three  clouds  and  finally  circling 
to  earth.  In  1905,  one  of  Professor  Montgomery's  parachute  jumpers 
(Maloney)  was  killed  through  an  accident  to  the  machine  in  starting 
from  the  ground.  Hot-air  balloons  rise  very  quickly  and  it  was 
necessary  to  provide  some  means  of  retarding  their  upward  rush. 
This  was  effected  by  ropes  running  through  rings,  and  in  Maloney's 
last  flight  one  of  these  ropes  caught  in  the  machine.  A  warning 
was  shouted  that  the  glider  had  been  broken,  but  the  operator 
evidently  did  not  hear  it.  He  cut  loose  from  the  balloon  at  a  height 
of  about  four  thousand  feet,  when  the  machine  immediately  turned 
over  and  he  descended  with  the  machine  upside  down.  Apparently, 
the  fall  was  not  any  faster  than  that  of  a  man  dropping  in  a  para- 
chute, and  when  examined  no  broken  bones  or  wounds  were  found, 
the  physicians  concluding  that  he  had  really  died  from  heart  failure. 
The  San  Francisco  disaster  put  a  stop  to  further  experiments  for 
several  years,  and  when  resumed  they  were  brought  to  a  close  by  the 
accidental  death  of  Professor  Montgomery  himself  in  October,  1911, 
while  making  a  glide  at  Evergreen,  California.  The  machine  was 
a  monoplane  glider,  and  for  getting  a  rapid  start  with  it,  a  runway  of 
grooved  tracks  had  been  built  down  the  side  of  the  hill.  A  gust  of 
wind  caught  the  machine  head  on  and  dashed  it  to  the  ground. 

SOARING  FLIGHT 

Countless  theories  have  been  offered  in  explanation  of  the 
phenomenon  of  soaring  flight,  but  from  the  great  number  that  have 
been  advanced  only  two  appear  to  afford  a  plausible  solution  of  the 
problem.  One  of  these  is  the  quite  common  conception  of  soaring 
flight  as  being  made  possible  by  rising  air  currents;  the  other  is  the 
action  and  reaction  theory  of  Professor  Montgomery  just  described. 
The  latter,  though  difficult  to  understand,  is  so  thoroughly  in  accord- 
ance with  the  phenomenon  that  actually  takes  place  as  to  leave  little 
doubt  of  its  accuracy.  It  is  quite  evident  that  birds  do  take  advantage 
of  rising  currents  to  perform  certain  feats,  but  soaring  flight  is  not 
dependent  upon  them. 

Early  Observations.  Andrews.  E.  F.  Andrews  has  observed 
that  gulls  following  a  steamer  traveling  against  a  stiff  head  wind, 
could  not  soar  fast  enough  to  keep  pace  with  the  vessel  and  would 
accordingly  flap  their  wings  until  they  reached  the  rising  current 


162 


THEORY  OF  AVIATION  65 

deflected  from  the  deck.  They  would  then  decrease  the  angle  of 
their  wings,  reducing  their  head  resistance  and  increasing  their 
speed  to  that  of  the  ship.  At  other  times,  when  running  with  the 
wind,  numbers  of  them  were  observed  soaring  about  the  vessel  in 
wide  circles,  rising  and  falling,  and  always  without  a  stroke  of  the 
wings.  Under  these  circumstances,  it  would  be  impossible  for  them 
to  take  advantage  of  a  rising  current  caused  by  the  ship,  and  a  local 
rising  current  in  midocean  would  not  alone  be  highly  improbable, 
but  it  would  not  travel  with  the  ship  as  the  birds  did.  Further 
observations  have  demonstrated  that  a  bird  can  soar  upward  on 
motionless  wings  without  the  assistance  of  a  rising  current.  For 
instance,  Andrews  closely  watched  a  turkey  buzzard  sailing 
over  a  field  at  a  height  of  about  fifteen  feet.  The  big  bird  flew  to 
within  a  very  short  distance  of  the  observer  and  then  without  once 
flapping  his  wings,  sailed  upward  to  a  height  of  a  hundred  feet  or 
more  in  less  than  half  a  minute  and  continued  to  soar  off  until  lost 
in  the  distance.  Releasing,  immediately  afterward  at  the  spot  where 
the  bird  had  risen,  some  light  cotton  fiber  provided  for  the  purpose, 
failed  to  reveal  any  rising  current  of  sufficient  strength  to  have  any 
marked  effect  on  the  bird,  as  the  cotton  quickly  fell  to  the  ground 
within  a  short  distance  from  the  place  it  was  liberated.  Wilbur 
Wright  is  sponsor  for  the  statement  that  the  Wright  biplane  glider 
will  glide  over  the  face  of  a  hill  whose  angle  is  so  flat  that  turkey 
buzzards  in  order  to  fly  over  the  same  course  will  be  compelled  to 
flap  their  wings.  But  as  the  result  of  his  observations,  Andrews 
is  of  the  opinion  that  the  birds  in  question  were  probably  not  real 
turkey  buzzards,  as  there  are  three  species  of  vultures  found  in  the 
southeastern  states,  viz,  the  carrion  crow,  the  black  vulture,  and  the 
turkey  buzzard.  The  only  distinguishing  feature  of  the  last-named 
variety  is  its  slightly  greater  size  and  its  red  head,  the  heads  of  the 
other  two  species  being  black.  The  flight  of  the  turkey  buzzard  is 
much  superior  to  that  of  the  black-headed  members  of  his  family. 
It  is  very  seldom  that  he  flaps  his  wings  and  when  he  does,  the  effort 
required  is  apparently  so  great  that  not  more  than  three  or  four 
wing  strokes  are  possible  without  stopping  for  a  rest.  The  other 
two  species  of  vulture  do  not  possess  the  wonderful  soaring  ability 
of  the  turkey  buzzard,  and  on  this  account  it  is  necessary  for  them 
to  flap  their  wings  at  short  intervals  throughout  their  flight. 


163 


66  THEORY   OF   AVIATION 

Andrews'  observations  have  included  numerous  instances  in  which 
turkey  buzzards  have  made  glides  terminating  several  hundred  feet 
higher  than  the  starting  point,  when  all  the  means  at  his  disposal 
failed  to  reveal  any  rising  current,  while  Victor  Lougheed  is  respon- 
sible for  the  statement  that  he  has  seen  a  condor  rise  from  a  fence 
post  in  California  and  soar  over  the  mountains  without  the  stroke 
of  a  wing,  when  no  rising  current  was  perceptible.  These  observa- 
tions seem  to  prove  that  a  force  like  gravity  can  act  on  a  body  such 
as  that  of  a  bird  in  such  a  manner  as  to  make  it  rise  against  the 
force,  just  as  a  sailboat  moves  against  the  force  which  is  propelling 
it.  Andrews  has  further  verified  his  theories  by  carrying  out 
experiments  with  a  glider  towed  behind  an  automobile  on  the  beach 
at  Daytona,  Florida.  When  the  tow  rope  was  slackened,  the  machine 
would  commence  to  glide  at  a  very  flat  angle,  and  flights  as  long  as 
two  miles  were  made  behind  a  machine  in  this  manner.  It  was 
intended  to  carry  the  experiments  further  by  releasing  the  glider 
and  soaring  to  earth,  but  an  accident  prevented  this.  The  experience 
of  both  Andrews  and  other  experimenters  before  him,  who  have 
tried  towing  a  glider  behind  an  automobile,  has  been  such  as  to  afford 
a  warning  to  the  student  to  strictly  avoid  all  forms  of  towing  flight. 
It  is  distinctly  dangerous,  as  a  machine  which  would  be  perfectly 
safe,  if  free,  is  made  as  erratic  as  a  child's  kite,  the  moment  a  rope 
is  attached  to  it. 

Historical  Records.  Soaring  flight  must  not  be  confused  with 
volplaning,  or  gliding  downward  by  taking  advantage  of  the  pres- 
sure of  the  air  beneath  a  plane  to  resist  the  force  of  gravity,  and  at 
the  same  time  taking  advantage  of  gravity  itself  to  gather  momentum 
and  make  short  upward  shoots,  thus  gaining  horizontal  distance. 
Soaring  may  be  described  best  as  gliding  by  the  force  of  the  wind 
without  loss  of  altitude,  or  as  shown  by  the  ability  of  the  turkey 
buzzard  and  condor,  with  a  voluntary  increase  in  altitude  when 
desired.  Human  volplaning  has  been  so  far  perfected  as  to  no  longer 
be  a  novelty,  if  indeed  it  does  not  surpass  the  master  performances 
in  nature.  But  human  soaring  is  a  much-neglected  art,  though 
capable  of  astonishing  development,  which  may  now  be  cultivated 
with  enhanced  facility  by  reason  of  the  increased  efficiency  of  the 
glider  and  the  aeroplane. 

The  permanent  art  of  passive  flight  dates  from  Lilienthal's 


164 


THEORY   OF   AVIATION  67 

experiments  near  Berlin  in  the  early  nineties,  though  long  previous 
to  that  time  some  wonderful  feats  of  gliding  and  soaring  of  both 
men  and  models  were  reported  by  reliable  witnesses.  Lilienthal 
made  numerous  glides,  several  hundred  feet  in  length  down  hill 
slopes,  sometimes  pausing  in  the  air  or  rising  considerably  above 
the  level  of  his  launching  place,  while  at  times  he  wheeled  about  and 
returned  almost  to  the  starting  point.  He  was  succeeded  by  various 
disciples  who  improved  the  control  of  the  glider  and  to  some  extent 
its  efficiency.  Professor  Montgomery,  a  contemporary  rather  than 
a  disciple  of  Lilienthal,  after  twelve  years  of  study,  launched  a  glider 
and  aeronaut  from  heights  which  far  surpassed  in  altitude  and  endur- 
ance all  gliding  records  up  to  the  present  time.  The  record  for  vol- 
planing in  a  power  machine,  which  really  becomes  a  glider  when  the 
motor  stops,  is  held  by  Lincoln  Beachey,  who  glided  sheer  down  to 
earth  in  a  Curtiss  biplane  from  an  elevation  of  12,654  feet,  during 
the  Chicago  Aviation  Meet  in  1911. 

The  records  for  soaring  are  briefer  and  some  are  not  so  well 
attested.  In  1859,  Captain  LeBris,  in  a  glider  patterned  after  an 
albatross,  soared  300  feet  in  the  air  and  descended  safely.  This  is 
given  on  the  authority  of  De  Landelle  who  wrote  a  history  of  aero- 
nautics published  in  1884.  Mouillard  is  reported  by  Chanute  to 
have  soared  138  feet  over  a  prairie  after  an  initial  run  and  jump 
across  a  roadside  ditch.  The  glider  in  this  case  was  strapped  to  his 
waist,  the  trials  taking  place  about  1890.  During  the  gliding  experi- 
ments of  Chanute  and  Herring,  one  of  the  operators  was  raised  by 
the  wind  to  a  height  of  about  forty  feet  and  then  landed  almost  in 
his  tracks  without  serious  shock.  Also,  lateral  glides  along  the  hill- 
side were  made,  one  forty-eight  seconds  in  duration,  which  showed 
the  possibility  of  patrolling  to  and  fro  in  such  places.  Atwood  relates 
that  while  flying  over  a  mountainous  country,  he  once  encountered 
an  upward  current  which  lifted  him  almost  a  thousand  feet,  while 
Orville  Wright,  during  the  1911  experiments  at  Kitty  Hawk  as 
already  described,  was  supported  in  his  glider  on  such  a  current  for 
nearly  ten  minutes,  sometimes  stationary,  again  gliding  forward  or 
backward,  and  sometimes  rising  to  a  considerable  height  above  the 
starting  point.  These  various  experiments  are  good  indications  of 
what  may  be  expected  when  the  possibilities  long  ago  revealed  by 
science  are  put  to  the  test  of  adequate  investigation. 


165 


68  THEORY   OF   AVIATION 

Theory  of  Soaring.  The  fundamental  postulates  of  the 
mechanical  theory  of  passive  flight  are  very  simple.  They  are 
summed  up  by  Lord  Rayleigh  in  the  following  paragraph: 

I  premise  that  if  we  know  anything  about  mechanics,  it  is  certain  that 
a  bird  without  working  its  wings  can  not,  either  in  still  air  or  in  a  uniform  hori- 
zontal wind,  maintain  its  level  indefinitely.  For  a  short  time,  such  maintenance 
is  possible  at  the  expense  of  an  initial  velocity,  but  this  must  soon  be  exhausted. 
Whenever,  therefore,  a  bird  pursues  its  course  for  some  time  without  working 
its  wings,  we  must  conclude,  either  (1)  that  the  course  is  not  horizontal,  (2) 
that  the  wind  is  not  horizontal,  or  (3)  that  the  wind  is  not  uniform. 

Rayleigh's  first  postulate  covers  the  case  of  volplaning,  which  is 
accomplished  on  a  generally  downward  course.  The  second  and 
third  postulates  comprise  all  cases  of  soaring  ever  yet  adequately 
observed  in  art  or  nature.  In  our  present  state  of  science  no  other 
cases  are  admissible.  Many  observers,  it  is  true,  testify  that  a  bird 

can  soar  in  a  uniform,  horizontal 

^L  wind  or  in  a  dead  calm,  which  is 

its  mechanical  equivalent  for  that 
purpose,  but  such  flight  is  be- 
yond the  power  of  aerodynamics 

^*^"^BB^V^  to  explain,  if,  indeed,  it  be  not 

^^  ^^  equivalent  to  perpetual  motion. 

Soaring,  then,  is  possible  only 
in  ascending  air  or  in  a  wind  of 
variable  velocity,  by  which  is  in- 
tended a  wind  that  varies  in  speed, 

Fig.  27.     Force  Diagram  for  a  Soaring  Plane     in  direction,  Or  in  both.      Ill  Other 

words,  it   is   possible  (1)  in   an 

ascending  flow  of  air;  (2)  in  a  horizontal  striated  flow,  in  which  the 
stream  lines  are  all  parallel  but  the  velocity  varies  in  neighboring 
striae  or  strata;  (3)  in  a  horizontal  wind  of  fluctuating  speed;  (4)  in 
a  horizontal  wind  of  fluctuating  direction,  either  horizontal  or  vertical. 
The  chief  types  of  maneuver  for  such  conditions  may  be  considered 
briefly  here,  as  also  the  prevalence  of  such  conditions.  Of  course, 
this  classification  does  not  hold  rigorously  in  nature,  but  may  be 
assumed  for  the  purpose  of  simplifying  the  analytical  treatment. 

Fig.  27  presents  the  well-known  graphic  analysis  of  soaring  in 
an  ascending  current  if  the  oblique  arrow  represents  the  relative 


166 


THEORY   OF   AVIATION  69 

wind  and  the  other  arrows  the  horizontal  and  vertical  components 
of  its  pressure  on  the  flier,  it  will  hover  still  in  space  when  the 
vertical  component  coincides  with  the  weight  and  the  horizontal 
component  just  neutralizes  the  head  resistance.  Obviously,  also, 
the  flier  will  advance  or  recede,  rise  or  fall,  according  as  these  com- 
ponents of  wind  force  prevail  or  are  overpowered.  If,  further,  the 
surface  be  tilted,  it  will  have  a  third  or  lateral  wind  force  tending 
to  produce  motion  sidewise,  so  that  the  flier  may  glide  to  right  and 
left  across  the  wind,  as  well  as  in  the  other  two  rectangular  directions. 
In  an  ascending  wind,  therefore,  a  passive  flier  can  hover  still,  or 
advance  in  any  direction.  This  form  of  flight  has  been  practiced 
from  time  immemorial  by  all  kinds  of  birds,  even  poor  sailers,  and  is 
easily  accomplished  by  any  skilled  aviator  under  favorable  conditions. 

Any  skilled  volplaner  who  wishes  to  practice  soaring  would,  there- 
fore, do  well  to  follow  the  long-standing  advice  of  mathematicians 
and  choose  a  sandy  slope  up  which  the  wind  blows  at  any  angle 
rather  in  excess  of  the  flattest  angle  of  descent  possible  in  still  air. 
The  slope  should  preferably  face  the  sea  or  a  broad  open  stretch  of 
level  land.  If,  furthermore,  the  slope  be  wide,  the  aviator  may  soon 
learn  not  only  to  hover,  to  advance,  and  to  recede,  but  also  to  patrol 
the  entire  slope  to  and  fro  laterally.  As  an  instance  of  such  procedure, 
Dr.  A.  F.  Zahm,  who  is  an  authority  on  the  subject  and  the  author 
of  the  present  synopsis  of  soaring  flight,  cites  the  fact  of  having  seen 
a  crow,  which  usually  beats  its  wings  continually  in  flight,  soar  to 
and  fro  on  rigid  pinions  along  a  stone  wall  over  which  a  stiff  wind 
was  blowing,  and  at  times  also  rise  and  descend,  advance  and  recede, 
then  instantly  take  to  violent  beating  when  caught  in  the  general 
current  away  from  the  wall. 

Conditions  for  Continuous  Soaring.  Obviously,  continuous  soar- 
ing is  possible  on  a  rising  current  whose  vertical  component  equals 
or  exceeds  the  slowest  possible  rate  of  descent  of  the  glider  when 
coasting  down  still  air.  If,  for  example,  a  bird  in  calm  air  can  glide 
at  a  speed  of  20  miles  an  hour  down  a  slope  of  one  in  ten,  it  can  soar 
continuously  in  a  current  rising  with  a  vertical  component  of  2 
miles  per  hour;  while  an  equally  efficient  flier  moving  60  miles  an 
hour  would  require,  to  maintain  soaring,  a  current  rising  at  no  less 
than  0  miles  per  hour.  From  this  it  follows  that  the  slowest  and  most 
amply  surfaced  gliders,  like  butterflies,  require  the  least  ascensional 


167 


70  THEORY    OF    AVIATION 

trend  of  air  for  soaring.  Still,  such  fliers  are  far  from  being  good 
soarers  because  of  their  incapacity  to  acquire  sufficient  speed  and 
momentum  to  cleave  swift  winds  and  drive  their  way  for  a  consider- 
able time  in  spite  of  unfavorable  conditions. 

Ascending  Winds.  Ascending  winds  due  mainly  to  uneven 
temperature  distribution  and  to  inequalities  of  terrene  prevail  very 
generally  over  the  globe.  Lilienthal  concluded  from  instrumental 
observation  that  the  general  trend  of  the  wind  is  three  degrees  upward. 
His  was,  of  course,  a  local  and  empirical  study.  But  on  principle 
it  may  be  qualitatively  affirmed  that  the  general  course  of  the  wind 
is  slightly  upward.  The  rising  air  is,  on  the  average,  warmer  than 
the  descending  air;  hence,  its  volumetric  displacement  is  greater  and 
consequently  its  general  direction  of  flow  is  slightly  upward.  This 
effect  is  intensified  where  the  air  from  a  surface  of  water  or  vegetation 
passes  over  a  barren  or  desert  soil.  Ascending  vortices  are  very 
abundant,  particularly  over  a  heated  terrene  exposed  to  direct  sun- 
shine. Meteorology  teaches  that  every  isolated  cumulus  and  thunder 
head  marks  the  top  of  a  rising  column  of  hot  air.  All  heated  slopes, 
especially  in  the  early  part  of  the  day,  produce  updrafts,  particularly 
if  they  be  long  and  barren.  Precipitous  islands  and  coastlands  cause 
strong  ascending  currents  which  the  sea  birds  know  so  well  how  to 
use.  Over  the  desert,  numerous  columns  of  sand  reveal  the  rising 
vortices  continually.  On  torrid  plains,  large  isolated  trees  have  a 
powerful  uprush  of  air  above,  initiated,  doubtless,  by  the  tree  itself 
from  the  hot  stratum  of  air  beneath.  Thus,  the  skilful  soaring  bird 
finds  abundant  elevators  as  he  coasts  about  the  atmosphere,  which 
may  be  used  to  prolong  his  meandering  glide  till  the  next  elevator  is 
encountered,  whether  this  be  a  vortex  or  an  upwardly  deflected  wind. 

Horizontal  Winds.  Soaring  in  a  truly  horizontal  wind  whose 
speed  varies  considerably  at  neighboring  levels,  or  in  different  strise 
at  the  same  level,  is  easy  to  understand  in  theory.  The  bird,  or  flier, 
acquires  sufficient  speed  in  the  swifter  stratum  to  enable  it  to  glide 
into  the  lower  stratum,  there  reverse  its  direction  and  return  in  the 
teeth  of  the  swifter  current,  to  be  again  caught  up  and  given  a  new 
impulse  as  before.  Many  instances  of  such  flight  are  reported  in 
nature,  but  none  in  human  art.  The  theory  has  been  presented  by 
Lord  Rayleigh  in  his  "Mechanical  Principles  of  Flight,"  by  Vogt  in 
"Engineering,"  and  by  various  other  writers,  but  the  actual  perform- 


168 


THEORY    OF    AVIATION 


71 


ance  still  challenges  the  skill  and  cunning  of  the  practical  aviator. 
The  fact  that  the  wind  moves  in  neighboring  strata  and  striae  is 
well  established,  but  it  is  still  to  be  proved  quantitatively  that  the 
rate  of  change  of  speed  is  quite  commonly  sufficient  to  support  pro- 
longed passive  flight. 

Horizontal  Winds  of  Pulsating  Character.  Soaring  in  a  horizontal 
wind  of  pulsating  speed  has  been  qualitatively  explained  by'Langley, 
and  quantitatively  studied  by  Chanute  and  others.  The  general 
theory  conceives  that  the  flier  faces  the  direction  of  the  wind,  rises 


53'"-     54™-      .55m-     56m-     57m- 58m 
Fig.  28.     Langley's  Record  of  Speeds  of  a  Pulsating  Wind 

and  drifts  backward  when  the  wind  freshens,  sinks  and  advances 
during  the  lull.  This  explanation  is  valid,  provided  the  horizontal 
acceleration  of  the  wind  be  sufficient.  Langley,  therefore,  recorded 
the  pulsations  of  wind  speed  by  means  of  very  light  cup  anemometers 
to  obtain  a  physical  basis  for  his  theory.  The  records,  Fig.  28,  show 
quite  remarkable  fluctuations  in  speed,  but  not  sufficient  to  maintain 
soaring  in  any  flier  of  art  or  known  nature  up  to  the  present.  The 
total  forward  resistance  of  a  well-formed  aerial  glider,  or  bird,  may 
be  taken  as  one-eighth  its  weight;  hence,  if  poised  stationary  in  its 


169 


72  THEORY   OF   AVIATION 

normal  attitude  of  flight,  it  will  be  just  sustained  by  a  direct  head 
wind  having  a  horizontal  acceleration  of  one-eighth  that  of  gravity, 
or  four  feet  per  second.  This  is  obviously  true  of  all  gliders,  whether 
swift  or  slow,  whose  total  resistance  equals  one-eighth  of  their  weight. 
Now,  the  most  favorable  parts  of  the  record  here  shown  nowhere 
exhibit  an  acceleration  so  great  as  four  feet  per  second  and,  on  the 
average,  show  far  less  than  that,  as  may  be  seen  by  scaling  the 
diagram.  Hence,  the  wind  here  recorded  was  wholly  inadequate  to 
support,  by  its  pulsative  force,  either  bird  or  man.  As  this  record  is 
a  fair  representative  of  all  those  published  by  Langley,  it  follows 
that  at  best  such  pulsations  can  merely  aid  in  soaring  when  happily 
and  adroitly  encountered;  but  that  they  can  not  fully  sustain  soar- 
ing at  any  level,  much  less  during  ascensional  flight  to  great  altitudes, 
or  migrational  flight  over  vast  distances.  This  conclusion  is  applica- 
ble even  to  those  gliders  which  are  reported  to  require  a  propulsive 
force  of  but  one-fifteenth,  or  one-twentieth  of  their  total  weight. 
Hence  to  account  for  soaring  in  a  horizontal  wind  of  fluctuating  speed, 
it  seerns  necessary  to  postulate  a  pulsating  breeze  of  far  greater 
acceleration  than  those  recorded  by  Langley  in  his  paper  on  "Internal 
Work  of  the  Wind."  Fuller  and  more  varied  records  of  the  pulsa- 
tions in  the  wind's  velocity  may  be  found  in  the  Interim  Report  for 
1909  of  the  British  Advisory  Committee  for  Aeronautics. 

In  a  horizontal  wind  that  pulsates  in  direction  merely -from  side 
to  side,  soaring  may  be  aided  by  the  alternate  impulses  of  the  air 
against  the  flier,  resisted  by  its  inertia.  If  the  wind  freshen  well  from 
the  right  quarter  and  the  flier  lists  to  port,  it  will  be  driven  to  port; 
then  if  the  wind  blow  promptly  from  the  left  quarter,  while  the  flier 
is  tilted  to  starboard,  it  will  have  its  acquired  component  of  momen- 
tum to  port  reversed  and  will  drift  to  the  right.  In  each  case,  the 
oblique  lift  on  the  wings  may  have  a  component  generally  forward, 
tending  to  overcome  the  entire  head  resistance.  The  magnitude  of 
this  forward  component  of  the  normal  pressure  on  the  tilted  flier 
is  easily  seen  to  be,  at  any  instant,  equal  to  the  product  of  such 
normal  force  multiplied  by  the  sine  of  the  angle  of  the  tilt  and  by 
the  sine  of  the  angle  between  the  quartering  wind  and  the  forward 
course.  If,  for  example,  each  of  these  angles  be  30  degrees  at  any 
instant,  the  propulsive  force  is  one-fourth  of  the  whole  normal  com- 
ponent, which,  of  course,  would  be  ample  to  overcome  all  resistance. 


170 


THEORY   OF   AVIATION  73 

Continuous  soaring  in  such  a  laterally  pulsating  current  would, 
however,  require  phenomenally  wide  and  rapid  fluctuations  of  wind 
direction,  and  great  alertness  on  the  part  of  the  flier.  The  case  is 
worth  notice  as  showing  that  a  glider  can  receive  both  support  and 
propulsion  from  a  quartering  wind,  and  can  even  tack  successfully, 
like  a  ship,  if  the  horizontal  fluctuations  in  direction  be  suitable. 
In  a  generally  horizontal  wind  that  undulates  up  and  down,  soaring 
may  be  aided  in  various  ways,  if  not  continuously  sustained.  If  the 
aerial  vibrations  be  strong  and  rapid,  as  in  a  fluttering  wind,  they 
may  exert  a  sculling  action  on  the  wing  as  a  whole,  or  on  its  flexible 
rear  margin.  In  such  case,  the  narrow  flexible  wing  of  the  bird 
would  be  more  effective  than  the  broad  stiff  wing  of  an  ordinary 
aeroplane,  though,  of  course,  narrow  and  pliable  pinions  can  be 
used  in  aeroplanes  and  gliders  to  adapt  them  to  soaring  in  fluttering 
winds.  Such  sculling  action  may  occur  in  wind  undulations  of  con- 
siderable period  and  amplitude,  as  where  the  air  follows  the  contour 
of  the  billows  in  a  heaving  or  tempestuous  sea,  particularly  if  the 
flier  glide  across  the  undulations  at  considerable  speed,  like  the  alba- 
tross, thus  greatly  increasing  the  apparent  frequency  of  the  rise 
and  fall  of  the  air. 

Mouillard  likens  soaring  in  such  heaving  air  to  the  motion  of 
a  marble  on  a  wavy  groove  in  a  vertical  plane,  which  a  skilled  hand 
moves  up  and  down  in  such  opportune  manner  as  to  cause  the  marble 
to  ascend  rapidly  on  a  long  wavy  slope.  The  comparison  is  a  good 
one,  except  for  the  f ac^  that  gliding  on  the  yielding  air  is  less  efficient 
than  sliding  or  rolling  on  a  rigid  track.  But  if  the  potential  energy 
can  be  rapidly  acquired  on  the  Mouillard  track,  perhaps  also  on  the 
aerial  track,  increased  altitude  can  be  attained  under  favorable  cir- 
cumstances, Dr.  Zahm  citing  a  case  where  he  has  caused  a  model 
glider  to  ascend  on  a  wavy  course  in  the  air  by  pulling  vertically 
down  on  it  intermittently  with  a  thread.  Such  gliding  appears  to 
represent  a  fairly  accurate  approximation  of  soaring  in  a  wind  oscil- 
lating rapidly  in  a  vertical  plane. 

In  case  the  undulations  of  the  air  be  due  to  a  vortex  rolling  about 
a  horizontal  axis  while  advancing  with  the  wind,  as  supposed  by 
some  writers,  the  bird  or  glider  might  remain  on  the  ascending  side 
of  the  vortex  and  thus  obtain  continuous  support  while  advancing 
with  the  speed  of  the  rolling  vortex,  whether  fast  or  slow.  Such  a 


171 


74  THEORY   OF   AVIATION 

performance  might  seem  marvelous  or  paradoxical  to  the  witness, 
since  the  rolling  vortex  must  be  quite  invisible,  but  the  feat  would 
be  no  more  remarkable  than  some  reported  by  aviation  experts 
who  claim  to  have  witnessed  the  passive  flight  of  aquatic  birds  for 
thousands  of  feet  just  over  the  surface  of  still  water  in  a  hardly  per- 
ceptible breeze.  The  rolling  vortex  of  Chanute  and  Herring  offers 
fascinating  possibilities.  The  aviator  need  only  saddle  his  glider 
deftly  on  this  transparent  Pegasus  to  go  kiting  over  all  creation. 
But  the  fine  art  is  to  locate  and  lasso  such  a  wild-wind  horse. 

Fig.  29  exhibits  typical  records  of  the  changes  in  wind  direction, 
both  horizontal  and  vertical,  obtained  by  Dr.  Zahm  by  means  of  a 
special  recording  wind  vane  exposed  in  a  clear  open  space  of  200 
acres,  and  in  a  wind  of  eight  to  twelve  miles  an  hour.  The  diagram 
shows  that  the  wind  veered  quite  frequently  10  degrees  in  a  short 

RECORD  OF  THE  YERT/CAL  VARfATYONS  OF  THE  W?ND 


RECORD  OF\THE  HORIZONTAL  VAR/AT/ONS  OF  THE  W/ND 


Fig.  29.     Curves  Showing  Changes  in  Horizontal  and  Vertical  Wind 
Directions  Recorded  by  Zahm 

interval  of  time,  and  not  infrequently  20  to  30  degrees.  In  strong 
winds  the  fluctuations  of  both  velocity  and  direction  are  generally 
more  marked  than  in  moderate  winds,  as  has  often  been  observed  in 
meteorological  records.  Hence,  they  furnish  a  good  physical  basis 
for  the  belief  that  soaring  may  be  materially  aided,  if  not  continu- 
ously sustained,  by  pulsating  winds. 

Aspiration.  According  to  Carl  E.  Myers,  the  solution  of  soaring 
flight  is  dependent  upon  the  phenomena  of  "aspiration."  Given  an 
undulatory  wind  power  whose  flowing  stream  of  waves  is  split  apart 
by  the  edge  of  an  intervening  surface  having  weight  below  to  pre- 
vent it  from  capsizing,  and  whose  rearward  surface  curves  slightly 
downward,  so  as  to  divert  the  undulating  waves  slightly  downward 
and  to  inspire  an  uplift  in  the  aeroplane,  and  we  have  the  phenomena 
of  aspiration,  as  a  result  of  this  "internal  work  of  the  wind,"  as  Langley 
termed  it.  Among  the  examples  of  this  power  of  the  wind,  Myers 


THEORY   OF   AVIATION  75 

cites  the  case  of  the  ball  floating  above  the  surface  of  a  flat  table, 
and  the  automaton  representing  a  magician  balancing  a  ball  in  air 
above  a  wand  and  transferring  it  from  this  wand  to  another  held  in 
the  other  hand.  In  one  case  the  ball  simply  danced  on  an  invisible 
jet  of  air  rising  under  considerable  pressure  out  of  an  inconspicuous 
hole  in  the  center  of  the  table,  while  in  the  other,  the  ball  was  con- 
trolled by  jets  of  air  alternately  issuing  first  from  one  wand  and 
then  from  the  other.  What  appeared  to  be  magic  of  a  high  order 
was  simply  wind.  Another  instance  was  that  of  the  captive  balloon 
operated  by  Myers  from  the  government  reservation  of  the  Navesink 
Twin  Lights,  at  Highland,  New  Jersey,  for  observation  and  the  report- 
ing of  the  yacht  races  for  America's  cup  some  years  ago.  As  this 
balloon  ascended  about  1,000  feet  above  the  brow  of  the  hill,  it  was 
pushed  over  and  down  the  steep  hill  by  the  rush  of  wind  which  came 
across  the  upper  flat  and  poured  down  the  slope  to  the  sea  like  an 
invisible  aerial  Niagara.  Thus  there  was  the  novel  exhibit  of  a  fully 
inflated  gas  balloon  with  its  passenger  captive  at  the  end  of  a  rope 
which  was  anchored  to  the  hilltop,  forced  down  below  and  brought 
near  the  sea  level  by  the  plunging  overflow  of  the  wind.  On  days 
when  the  wind  blew  off  the  sea  and  uphill,  the  balloon  ascended  with 
it,  even  when  half  full  and  otherwise  unable  to  lift  itself  and  its  pas- 
senger, just  like  a  great  parachute  or  umbrella  when  the  wind  indented 
the  under  or  slack  side.  It  was  merely  a  gas  kite  and  a  man-sized  kite 
would  have  done  as  well.  Wind  and  surface  did  the  lifting  and  it 
soared  and  hovered.  i^.s  the  result  of  this  experience,  Myers  under- 
took a  series  of  experiments  from  which  he  evolved  the  theory  of 
"undulatory  flight."  Any  undulatory  movements  of  surfaces  will 
produce  undulatory  movements  of  air  and,  conversely,  undulatory 
progressive  movements  or  waves  of  air  impart  force  or  motion  trans- 
versely to  the  line  of  flow.  Thus  a  flag  wriggles  in  the  wind,  wasting 
its  power  in  flaps.  The  experiments  were  carried  out  by  means  of 
kites  and  resulted  in  the  evolution  of  the  "Texas  Self-Flying  Kite/'  of 
which  Myers  supplied  one  hundred  to  the  United  States  government 
for  the  artificial  rain-fall  experiments  carried  out  in  Texas  in  1891. 
The  kites  were  employed  for  firing  charges  of  dynamite  at  great 
altitudes.  Chanute  considered  this  "a  very  interesting  example  of 
partial  aspiration"  and  devotes  a  number  of  pages  in  "Progress  of 
Flying  Machines"  to  the  spectacle  of  the  flight  of  these  kites,  three 


173 


76  THEORY   OF   AVIATION 

miles  up  in  the  air,  and  their  disappearance  rising  higher,  ten  miles 
distant.  From  this  Chanute  came  to  the  conclusion  that  "inanimate 
surfaces  cunningly  balanced  and  continually  balanced  could  fly." 
The  veteran  engineer  Lancaster  reached  the  same  conclusion  many 
years  previous,  as  in  an  address  to  the  meeting  of  the  Associated 
Civil  Engineers  at  Buffalo  thirty  years  ago,  he  declared  that  he 
had  repeatedly  built  "effigies"  which  arose  from  his  hand  and  mounted 
into  mid-air  out  of  sight — a  statement  which  aroused  so  much  derision 
as  to  practically  drive  him  into  exile.  In  support  of  his  claims,  Lan- 
caster carried  out  extensive  observations  of  birds,  and  relates  that, 
on  one  occasion,  concealed  in  a  canvas  covering  painted  to  repre- 
sent a  dead  tree  top,  he  has  watched  a  large  bird,  the  gannet,  poised 
within  reach  in  mid-air  with  its  eyes  closed,  balanced,  motionless 
with  only  an  occasional  slight  ruffling  of  its  plumage.  When  touched 
with  a  pole,  its  eyes  opened,  and,  disconcerted,  it  slid  back  a  few 
feet,  then  regained  its  former  position  and  repose. 

A  bird's  wing  is  a  complex  combination  of  curved,  stiff,  and 
elastic  surfaces — the  curves  and  stiffness  being  greatest  forward, 
and  the  flexibility  and  capacity  for  separation  being  greatest  aft, 
or  in  the  line  of  undulatory  air  flow.  Wings  move  or  operate  upon 
fixed  pivots,  at  any  angle  or  inclination,  controllable  by  will  or  power, 
and  also  automatically  by  wind  or  gravity.  The  wind  never  flows 
"straight  along"  and  in  its  general  direction  it  never  ceases  to  vibrate, 
oscillate,  or  undulate  in  all  ways  or  directions,  as  an  elastic  flowing 
stream,  acting  forcibly  upon  any  suitably  arranged  and  adapted  sur- 
faces, to  urge  the  complex  whole  forward  or  buoy  it  up,  with  no  power 
lost  save  through  friction.  The  bird  is  a  balanced,  pendulous  weight, 
wholly  and  in  parts.  His  vital  functions  render  his  flying  features 
less  competent  than  an  inanimate  structure  of  equal  flying  power 
may  be.  Myers  states  this  not  as  the  problem,  but  as  its  solution, 
and  adds  that  "any  apparatus  fairly  conforming  to  the  conditions  will 
fly  or  float  in  due  proportion  to  its  structure" 

MODERN  AERODYNAMIC  RESEARCH 

There  is  yet  so  much  to  be  learned  regarding  atmospheric  laws 
and  their  influence  upon  flight,  that  well-equipped  experimental 
laboratories  are  indispensably  necessary  to  the  further  progress  of 
aviation.  Just  as  the  initial  success  of  the  Wright  Brothers  was  the 


174 


THEORY   OF  AVIATION  77 

culmination  of  years  of  scientific  research  which  demonstrated  the 
worthlessness  of  many  theories  that  for  years  previous  had  been 
regarded  as  well  established,  so  the  development  of  the  future  will 
be  the  result  of  consistently  carried  out  lines  of  investigation,  rather 
than  the  outcome  of  chance  discovery.  The  practical  use  of  the 
aeroplane  in  the  hands  of  such  a  large  and  rapidly-increasing  number 
of  aviators  will  undoubtedly  lead  to  improvement  in  construction  and 
design,  but  for  that  thorough  knowledge  of  the  principles  which  is 
essential  to  increased  efficiency  and  finality  in  design,  we  must  look 
to  the  scientist  and  his  laboratory. 

Aerodynamic  Institute  of  Kutchino.  It  is  somewhat  of  an 
anomaly  that  the  most  important  and  best-equipped  laboratory 
should  be  found  in  a  country  which  has  done  least  for  the  progress 
of  aviation,  that  is,  the  Aerodynamic  Institute  of  Kutchino,  near 
Moscow,  Russia.  This  was  established  several  years  ago  by  a  wealthy 
scientist,  M.  Riabouchinsky,  and  is  maintained  by  its  founder. 

Propeller  Experiments.  One  of  the  first  researches  attempted 
was  a  study  of  air  resistance,  an  artificial  and  easily  controlled  cur- 
rent of  air  being  produced  in  a  tunnel  for  this  purpose.  This  tunnel 
is  horizontal,  48  feet  long  by  4  feet  in  diameter,  and  is  equipped 
with  an  electric  fan  39  inches  in  diameter  to  draw  air  through  it, 
as  it  was  found  that  the  current  produced  by  aspiration  was  more 
uniform  than  that  set  up  by  forcing  air  into  the  tunnel.  The  models 
to  be  tested  are  placed  inside  the  tunnel,  which  is  equipped  with 
conveniently-placed  windows  for  observation.  The  small  Caselli 
anemometers  are  suspended  within  the  tunnel  by  light  steel  wires, 
one  fixed  at  the  axis,  the  other  movable.  The  indications  of  the 
former  are  found  to  be  always  directly  proportional  to  the  speed  of 
the  electric  fan.  The  wall  and  floor  of  the  room  were  found  to  affect 
the  regularity  of  the  air  current  when  the  tunnel  was  open,  so  that  it 
was  covered  with  a  light  metal  grating,  but  this  did  not  prove  satis- 
factory and  it  was  replaced  by  a  series  of  screens  between  the  end  of 
the  tunnel  and  the  wall  without  attaining  the  result  desired.  Finally, 
a  cylindrical  cap  about  7  feet  in  diameter  by  11  feet  long  into 
which  the  end  of  the  tunnel  penetrates  6  feet,  was  adopted.  This 
cap  is  made  of  wood  and  is  lined  with  coarse  cotton  stuff,  while  the 
tunnel  itself  is  of  sheet  steel.  From  this  excellent  results  are  obtained, 
the  mean  difference  between  the  greatest  and  lowest  velocities  in  the 


175 


78 


THEORY   OF   AVIATION 


tunnel  being  approximately  yV  inch  per  second.  The  tunnel  is 
employed  for  various  researches,  including  a  study  of  the  movement 
of  air  propellers  in  a  current.  Maxim  observed  that  when  the  wind 
blows  at  right  angles  to  the  axis  of  a  propeller,  its  propulsive  force  is 
increased,  and  this  has  been  verified  by  Professor  Joukovsky  in 
experiments  made  to  determine  the  variations  in  the  lifting  power 
and  the  work  performed  by  the  screw,  in  relation  to  the  velocity  of 
a  current  at  right  angles  to  its  axis. 

These  experiments  were  carried  out  as  follows:  A  two-bladed 
propeller  12  inches  in  diameter  with  its  blades  inclined  6  degrees,  is 
driven  by  an  electric  motor  A,  Fig.  30,  attached  to  a  steel  frame 
inserted  in  the  tunnel.  This  frame  can  turn  freely  about  a  horizontal 
axis  at  B,  while  the  other  end  is  terminated  by  a  rod  C,  passing 

through  the  wall  of  the  tube. 
To  this  rod  is  attached  a  cord 
passing  over  a  pulley  E,  and 
supporting  a  scale  pan  F.  By 
placing  weights  in  this  pan, 
the  frame  can  be  balanced 
with  the  screw  at  rest  or  in 
motion.  The  difference  be- 
tween the  weights  in  the  two 
cases,  multiplied  by  the  ratio 
between  the  arms  of  the  lever 
BD  and  BA,  gives  the  lifting 
power  of  the  propeller  tested. 
The  work  performed  by  the 
propeller  is  ascertained  by 

Colonel  Renard's  method.  The  motor  is  mounted  on  pivots  so  that  it 
may  turn  freely.  To  the  motor  is  attached  a  ring  G,  about  2  inches  in 
diameter,  over  which  passes  a  cord,  traversing  the  wall  of  the  tunnel, 
passing  over  the  pulley  //,  and  terminating  in  the  scale  pan  F'.  By 
the  effect  of  the  reaction,  the  motor  is  impelled  to  rotate  in  a  direction 
opposite  to  that  of  the  propeller.  The  moment  of  the  force  turning 
the  motor,  which  is  equal  to  that  of  the  force  turning  the  propeller, 
is  obtained  by  multiplying  the  weight  (added  to  that  of  the  scale 
pan  F'  during  the  rotation  of  the  propeller)  by  the  radius  of  the  ring 
surrounding  the  motor,  and  the  work  performed  is  obtained  by  multi- 


Fig.  30. 


Air  Propeller  Revolving  in  Air  Current 
Perpendicular  to  Its  Axis 


176 


THEORY   OF   AVIATION  79 

plying  this  moment  by  twice  the  number  of  turns  per  second  made 
by  the  propeller.  These  experiments  show  that  the  lifting  force  of 
the  propeller,  as  well  as  of  the  ratio  between  this  force  and  the  energy 
expended,  increases  with  the  velocity  of  a  current  of  air  at  right 
angles  to  the  axis. 

The  most  important  researches  made  at  the  Kutchino  laboratory 
naturally  relate  to  propeller  design.  Riabouchinsky  classifies  sus- 
taining apparatus  in  four  groups:  (1)  The  car  group,  including 
ordinary  cars,  aerial-paddle  wheels,  and  apparatus  comprising  wings 
with  valves.  (2)  The  screw  propeller  group,  including  the  screw, 
the  aeroplane  (which  is  regarded  as  the  blade  of  a  propeller  of  infinite 
diameter),  and  apparatus  with  wings  vibrating  in  a  plane  perpen- 
dicular to  the  direction  of  the  thrust.  The  action  of  all  apparatus 
in  this  group  is  based  upon  the  properties  of  the  inclined  plane. 


Fig.  31.     Apparatus  for  Studying  the  Impact  of  a  Current  on  a  Surface 

(3)  The  centrifugal  pump  group,  comprising  apparatus  in  which  air 
attracted  by  the  barometric  depression  formed  at  the  center  is 
projected  outward  by  centrifugal  force  and  then  diverted  in  the 
proper  direction  by  fixed  surfaces.  (4)  The  weather  vane  group. 
The  operation  of  apparatus  of  this  class  is  illustrated  by  experiments 
with  an  elongated  rectangle  in  rotation  about  an  axis  at  right  angles 
to  the  direction  of  the  air  current.  In  regard  to  the  study  of  the 
inclined  plane,  Lilienthal  pointed  out  that  the  specific  resistance 
experienced  by  each  element  of  a  sustainer  with  wings  may  be 
twenty  times  as  great  as  that  of  a  plane  moving  uniformly  in  a 
straight  line.  He  attributed  this  increase  of  pressure  to  the  inertia 


177 


80 


THEORY    OF    AVIATION 


of  the  surrounding  air.  Joukovsky  explains  the  increase  by  the 
formation  of  air  waves  through  the  vibration  of  the  wings.  Goupil 
also  has  observed  that  the  mean  pressure  per  unit  of  surface  in  the 
case  of  an  alternating  and  accelerated  rotary  motion  is  greater  than 
in  uniform  motion  in  a  straight  line.  He  accounts  for  the  increase, 
partly  by  the  inertia  of  masses  of  air  clinging  to  the  surfaces  and 
partly  by  the  increase  of  the  relative  velocity  of  the  current  which 
meets  each  element  of  the  surface  in  consequence  of  the  centrifugal 
acceleration. 

Riabouchinsky  began  by  studying  a  sustainer,  the  blades  of  which 
had  an  alternating  rectilinear  motion  and  subsequently  determined 
the  specific  resistance  for  uniform  circular  motion.  In  the  latter 
case,  he  finds  the  coefficient  of  resistance  equal  to  0.885.  For  the 

purpose  of  studying  the  effect  of  the  im- 
pact of  a  current  upon  a  surface  he  de- 
vised the  apparatus  shown  in  Fig.  31, 
composed  of  two  planks  DD,  connected 
by  cross  ties  and  forming  a  sort  of  raft, 
which  can  descend  the  current  of  a 
stream,  guided  by  the  wire  (7.  Upon  the 
raft  is  mounted  the  apparatus  shown  in 
the  enlarged  detail  illustration  of  Fig.  32, 
consisting  of  a  tube  B,  6  inches  in  diam- 
eter, with  "an  indicator  E,  registering  the 
pressure  in  the  tube  upon  the  chronograph 
cylinder  F.  B  is  L-shaped,  its  horizontal 
member  containing  a  piston  rigidly  attached  to  an  aluminum  disk 
H,12  inches  in  diameter  and  ^  inch  thick.  The  tube  B  is  filled  with 
water  and  the  board  G  upon  which  it  rests  is  capable  of  sliding  with 
some  friction  in  grooves  cut  in  the  cross  ties,  Fig.  31.  The  post  A 
allows  the  raft  to  pass,  but  suddenly  stops  the  board  G,  the  pres- 
sure thus  produced  being  recorded  on  the  chronograph  cylinder. 

To  determine  the  components  of  the  pressure  of  an  air  current 
upon  an  inclined  plane,  the  apparatus  shown  in  Fig.  33  is  employed. 
The  vertical  axis  A  turns  in  ball  bearings  CC,  and  can  be  fixed  in 
any  position  in  the  tube  B  by  the  screw  P.  A  plane  surface  E  is 
attached  to  the  lower  end  of  the  rod,  while  the  upper  one  carries  a 
counterpoise  T  and  an  index  I.  To  the  tube  is  fitted  a  copper  circle 


Fig.  32. 


Details  of  the  Recording 
Part  of  Fig.  31 


178 


THEORY    OF    AVIATION 


81 


Q,  24  inches  in  diameter  and  divided  into  degrees.  The  tube  swings 
on  the  pivots  GG  and  is  brought  back  to  the  vertical  by  means  of 
a  beam  and  scale  pans.  By  placing  the  required  weight  in  the  pans, 
the  pressure  exerted  upon  the  plane  can  be  balanced  and  measured. 
By  turning  the  axis  A  in  the  tube,  the  plate  E  can  be  caused  to 
meet  the  current  at  different  angles,  and  the  components  of  the 
pressure  for  any  given  inclination  can  be  obtained  by  turning  the 
graduated  circle  M.  Furthermore,  by  fixing  the  beam  of  the  balance 
and  unscrewing  P,  the  position  of  the  center  of  pressure  can  be 
determined,  if  the  plate  E  is 
replaced  by  a  plate  capable  of 
turning  about  the  points  CC, 
as  shown  in  the  small  illustra- 
tion at  the  right,  Fig.  33.  It  is 
found  that  the  displacement  of 
the  center  of  pressure  as  a  func- 
tion of  the  angle  of  incidence 
depends  not  only  upon  the  dis- 
tribution of  pressure  on  the  front 
of  the  plane,  but  to  a  still  greater 
degree  upon  the  reduction  of 
pressure  at  the  back.  This  re- 
duction is  greatest  near  the  for- 
ward edge. 

Lifting  propellers,  such  as 
are  employed  in  helicopters, 
have  been  studied  with  the  aid 

of     three      tVDCS     Of     aDDaratUS.      Fig-  33'     APParatus  for  Measuring  Components 
J  r  Of  pressure  on  Inclined  Plane 

One  of  these  is  a  modification 

of  Renard's  double  dynamometric  balance,  from  which  it  differs 
only  in  having  the  propeller  placed  some  6  feet  above  the  motor, 
so  that  it  operates  in  a  perfectly  clear  space.  In  order  to  meas- 
ure with  precision  the  moment  of  resistance,  the  propeller  must 
be  arranged  to  drive  the  air  backward.  The  angular  velocity  is 
measured  by  means  of  a  seconds  clock,  which  is  started  and  stopped 
by  an  electromagnet  after  each  one  hundred  revolutions  of  the  pro- 
peller. The  propeller  and  motor  are  suspended  by  means  of  cords 
upon  two  pairs  of  knife-edges,  of  which  one  is  parallel  and  the  other 


179 


82 


THEORY  OF  AVIATION 


perpendicular  to  the  axis  of  the  propeller.    This  balance  serves  for 
testing  propellers  of  from  20  inches  to  10  feet  in  diameter. 

The  second  apparatus,  Fig.  34,  is  for  the  purpose  of  testing 
model  propellers,  measuring  from  8  to  20  inches  in  diameter,  by 
determining  separately  their  thrust  and  moment  of  resistance.  In 
this  apparatus  the  axis  of  the  motor  M  is  vertical,  and  its  extension 
(the  shaft  CC)  ends  in  a  bevel  gear  transmission  D  by  which  the 

propeller  H  is  driven.  The  vertical  shaft 
C  is  free  to  rise,  sink,  and  revolve,  and 
its  weight  and  that  of  the  motor,  etc.,  is 
counterbalanced  by  the  pan  and  pulley 
system  KY.  The  whole  mechanism  is 
pivoted  on  the  knife-edge  A,  so  that  when 
the  propeller  is  revolving,  its  thrust  may 
be  measured  by  a  spring  dynamometer, 
the  deflection  being  indicated  by  the 
pointer  at  the  top.  With  this  apparatus 
very  interesting  researches  have  been 
made,  the  results  being  published  in  a 
series  of  bulletins  issued  by  the  Institute. 
The  frictional  resistance  of  the  air  to 
the  motion  of  a  surface  is  studied  with 
the  aid  of  an  apparatus  consisting  of  an 
endless  band  of  rubber,  covered  on  both 
sides  with  cloth  and  stretched  over  two 
hollow  cylinders  20  inches  in  diameter, 
the  band  itself  being  about  5  feet  wide. 
One  of  the  cylinders  is  turned  by  a  14- 
horse-power  electric  motor.  Between  the 
two  cylinders  and  between  the  upper  and  lower  halves  of  the  travel- 
ing band  is  a  smooth  horizontal  table  40  feet  long  by  6  feet  wide. 
Eiffel  Aerodynamometric  Laboratory.  Gustave  Eiffel,  the  builder 
of  the  well-known  Eiffel  Tower  at  Paris,  has  carried  out  a  long  series 
of  experiments  of  considerable  value,  and  the  Eiffel  Aerodynamo- 
metric Laboratory  is  probably  the  most  important  in  France,  where 
aviatidn  long  since  reached  the  status  of  an  industry. 

Wind  Pressure  Experiments.  M.  Eiffel  undertook  to  procure  accu- 
rate data  concerning  wind  pressures,  in  1903.  From  the  first  platform 


Fig.  34.     Apparatus  for  Testing 
Model  Propellers 


180 


THEORY   OF   AVIATION 


83 


181 


84  THEORY  OF  AVIATION 

of  the  tower  was  suspended  a  steel  cable,  increasing  in  diameter  as 
it  approached  the  bottom.  A  device,  designed  to  be  dropped  along 
this  cable,  was  carried  on  a  frame  with  two  powerful  vertical  leaf 
springs  fixed  to  the  halves  of  two  sleeves,  placing  the  latter  under 
considerable  pressure.  Wood  liners  were  inserted  in  the  sleeves  so  that 
when  the  apparatus  reached  the  cylindrical  part  of  the  cable,  the 
conical  section  spread  the  sleeves  against  the  pressure  of  the  springs, 
which  exerted  an  effective  braking  effort.  The  frame  carries  a  recording 
drum  rotated  by  a  worm  shaft  actuated  by  a  friction  roller  on  the 
cable.  The  plane  to  be  tested  was  fixed  to  the  lower  part  of  a  stem 
free  to  move  upward  against  a  spring,  the  upper  part  of  the  stem 
carrying  a  needle  which  bore  against  the  drum.  This  heavy  apparatus 
dropped  from  a  height  of  377  feet,  and  during  311  feet  of  its  course, 
before  the  braking  action  began,  it  attained  a  velocity  of  131  feet 
per  second. 

The  air  resistance  expanded  the  accurately  calibrated  spring, 
causing  the  registering  needle  to  rise  on  the  drum,  which  rotated  at 
a  speed  proportionate  to  the  velocity  of  the  drop,  recording  the  air 
resistance  for  every  point  of  the  descent.  This  method  naturally  had 
its  limitations,  because  it  was  possible  to  ascertain  only  the  total 
resistance  offered  to  a  plane  when  falling  at  a  given  velocity.  Much 
interesting  data  was  obtained,  but  the  possibilities  of  the  apparatus 
were  soon  exhausted.  It  is  generally  conceded  that  more  practical 
results  are  obtainable  by  moving  the  surface  to  be  tested  through 
the  air,  thus  securing  conditions  more  closely  approaching  the  normal, 
but  there  are  so  many  difficulties  in  the  way  of  extending  this  line  of 
research  and  making  accurate  observations,  that  Eiffel  found  it  neces- 
sary to  follow  the  lead  of  Maxim  and  other  experimenters  by  employ- 
ing stationary  surfaces  in  a  current  of  air. 

In  order  to  obtain  accurate  data  in  this  manner,  the  plane  must 
be  in  a  cylinder  of  air  of  sufficient  diameter  to  avoid  influencing  the 
outer  stream  lines  by  its  pressure.  The  surface  tested  must  not  be 
too  small  and  it  was  found  that  the  diameter  of  the  air  current 
should  not  be  less  than  5  feet.  The  installation,  which  has  been  in 
use  for  some  time,  is  located  in  a  building  adjoining  the  Eiffel  Tower 
and  is  shown  in  section  in  Fig.  35.  It  consists  of  a  Sirocco  ventilator 
11  feet  in  diameter,  and  a  fan  G,  5  feet  9  inches  in  diameter,  which, 
with  its  masonry  setting,  has  a  total  height  of  18  feet.  The  venti- 


182 


THEORY   OF   AVIATION 


85 


lator  is  driven  by  a  70-horse-power  electric  motor  //,  at  a  speed  of 
40  to  200  r.p.m.,  by  means  of  which  the  velocity  of  a  cylinder  of 
air  5  feet  in  diameter  may  be  varied  from  16  to  65  feet  per  second. 
The  air  receiver  or  collector  B  is  built  up  of  a  wood  frame  covered 
with  rubber  balloon  fabric;  its  largest  diameter  is  10  feet  or  just 
double  the  aperture,  and  its  length  is  about  8  feet.  The  object  of 


Fig.  36.     Method  of  Testing  Models  of  the  Eiffel  Aerodynamometric  Laboratory 

this  collector  is  to  provide  a  slight  compression  of  the  air,  so  as  to 
favor  the  regularity  of  the  stream  lines.  However,  if  the  air  were 
drawn  through  an  unobstructed  aperture,  the  horizontal  column 
would  be  broken  up  into  a  mass  of  whirls,  so  that  to  obtain  perfectly 
parallel  stream  lines,  the  opening  is  fitted  with  a  grid  J,  which  is 
shown  in  Fig.  36,  built  up  of  thin  sheet  metal  similar  to  a  honeycomb 


183 


86 


THEORY   OF   AVIATION 


automobile  radiator,  each  cell  being  4  inches  square  by  10  inches 
long.  These  dimensions  were  not  based  upon  any  settled  data;  but 
were  first  adopted  experimentally  and  retained  after  proving  satis- 
factory in  operation.  Opposite  this  grid  is  the  short  cone  F,  Fig.  35, 
around  the  opening  of  the  tunnel,  at  the  end  of  which  is  placed  the 
ventilator,  the  distance  between  the  two  apertures  being  11  feet 


Fig.  37.     Detailed  View  of  Monoplane  Model  under  Test  at  the  Eiffel  Laboratory 

9  inches.  It  was  noticed  at  first  that  the  air  broke  up  into  whirls 
immediately  in  front  of  the  aperture  so  that  it  was  covered  with  a 
wire  netting  having  a  mesh  of  .39  inch,  another  wire  netting  being 
placed  about  3  feet  in  the  tunnel.  With  this  arrangement,  the  air 
current  is  so  perfectly  cylindrical  that  when  traveling  at  the  highest 
velocity  there  is  not  the  slightest  draft  in  the  experimental  room. 


184 


THEORY   OF   AVIATION  87 

This  room  CC  is  in  the  shape  of  a  T  with  one  part  parallel  to 
the  side  of  the  building.  It  contains  a  table  with  the  recording  instru- 
ments and  a  switchboard.  The  weighing  machine  E  for  measuring  the 
wind  pressure  is  on  a  platform  suspended  from  an  upper  story.  The 
plane  D  to  be  tested  is  attached  at  its  center  to  a  piece  hinging  on 
the  end  of  a  horizontal  rod,  Fig.  36,  and  is  also  attached  to  a  sliding 
piece,  shown  in  detail  in  Fig.  37,  capable  of  being  fixed  by  a  set  screw 
a  few  inches  along  the  rod,  so  that  the  plane  can  be  turned  round  180 
degrees  and  fixed  in  any  position.  The  horizontal  rod  is  clamped  in 
a  sleeve  at  the  bottom  of  a  vertical,  cast-steel  rod  contained  in  a 
copper  casing  of  larger  diameter,  and  presenting  a  beveled  edge  in 
the  axis  of  the  stream  lines,  so  as  to  offer  the  minimum  resistance. 
The  vertical  rod  is  bolted  to  the  platform  of  the  weighing  machine, 
which  is  carried  on  two  sets  of  knife-edges,  one  set  turned  downward 
and  the  other  upward.  This  is  necessary  for  measuring  the  pressure 
when  the  plane  is  inclined  up  or  down.  The  platform  is  made  to 
rest  on  one  or  the  other  of  the  knife-edges  by  shortening  or  lengthening 
the  rod  from  the  platform  to  the  cross  beam  by  means  of  a  cam, 
and  when  not  in  use  the  platform  is  raised  to  bring  the  knife-edges 
out  of  contact  with  the  grooves  by  a  lever  with  a  counterweight. 
This  weighing  machine,  which  was  constructed  especially  for  the 
installation,  is  sensitive  to  half  a  gramme. 

In  testing  a  plane,  the  equilibrium  is  obtained  by  weighting  the 
balance  with  the  knife-edges  alternately  in  their  grooves,  before  the 
air  current  is  passed,  through  the  experimental  room.  The  latter  is 
then  traversed  by  a  current  of  given  velocity,  determined  by  the 
speed  of  the  ventilator,  as  regulated  by  the  rheostat.  This  velocity 
is  gauged  by  a  manometer  communicating  between  the  air  current 
and  the  still  air  of  the  outer  shed,  and  also  by  a  Pitot  tube  placed 
in  the  current  and  connected  with  a  manometer  which  also  com- 
municates with  the  still  air.  Results  are  further  verified  by  various 
anemometers  and  the  differences  between  the  two  are  so  small  as  to 
be  inappreciable  from  the  viewpoint  of  general  results. 

Having  ascertained  the  air  velocity,  the  balance  is  again  weighted 
with  the  knife-edges  in  contact,  first  on  one  side  and  then  on  the 
other,  and  the  plane  is  then  turned  180  degrees,  when  the  equilibrium 
is  effected  on  the  corresponding  edges.  These  operations  provide 
three  equations  for  determining  the  total  pressure,  the  direction,  and 


185 


88  THEORY   OF   AVIATION 

the  center  of  pressure.  Another  method  of  determining  the  center  of 
pressure  consists  in  placing  the  plane  vertically  between  the  points 
of  two  rods,  the  ends  of  the  plane  being  drilled  so  that  it  may  be 
held  in  any  position.  The  plane  is  secured  by  a  clip  on  the  lower 
rod,  to  which  is  fixed  a  circular  plate  of  wood  with  the  angles  marked 
on  the  edge  and  corresponding  with  marks  on  the  fixed  frame.  When 
exposed  to  the  air  current,  the  plane  pivots  round  more  or  less, 
according  to  its  curvature,  and  the  angle  is  read  off  to  give  its  center 
of  pressure.  This  method  might  be  expected  to  lack  precision,  but 
the  results  agree  with  those  provided  by  the  weighing  machine. 

For  ascertaining  the  wind  pressure  at  different  parts  of  the 
plane,  the  instruments  employed  are  a  Pitot  tube  and  a  Schultze 
micromanometer,  and  it  is  mounted  on  a  frame  sliding  on  rails  to 
allow  of  its  being  brought  in  front  of  the  aperture.  Any  desired 
inclination  is  obtained  by  means  of  wires,  and  the  plane  itself  is 
drilled  with  a  number  of  holes  which  are  filled  with  screws  flush 
with  the  surface.  At  the  point  where  it  is  desired  to  ascertain  the 
pressure,  the  screw  is  removed  and  replaced  by  a  threaded  plug.  On 
the  side  subjected  to  the  wind  pressure  the  plug  is  flush  with  the 
surface,  while  on  the  other  side  it  carries  a  rubber  tube  connected 
with  the  micromanometer.  The  pressure  can  thus  be  obtained  at 
any  point  on  either  side  of  the  plane.  Highly  interesting  data  have 
been  obtained  with  this  apparatus,  and  as  evidence  of  the  accuracy 
of  the  method  it  may  be  mentioned  that  the  sum  of  the  pressures 
obtained  over  the  surface  corresponds  exactly  with  the  total  given 
by  the  weight  bridge.  It  is  thus  possible  to  obtain  the  center  of 
pressure,  the  total  pressure,  and  the  pressure  at  any  given  point  on 
either  side  of  the  plane.  Another  valuable  factor  is  the  disturbance 
of  the  stream  lines  caused  by  the  presence  of  the  plane.  This  is 
ascertained  by  attaching  light  filaments  to  the  plane  or  to  fine  wires, 
and  by  observing  their  movements  it  is  possible  to  sketch  plans  of 
the  air  whirls  around  and  behind  the  plane. 

It  is  sometimes  argued  that  experiments  with  a  fixed  surface  in 
a  current  of  air  have  little  practical  value  for  purposes  of  aviation, 
for  the  reason  that  these  conditions  are  contrary  to  those  governing 
the  flight  of  aeroplanes.  The  experiments  are  carried  out  under  one 
of  many  conditions,  and  this  one  is  met  with  only  when  the  aero- 
plane is  at  a  standstill  against  the  wind.  It  is  obvious,  however, 


186 


THEORY   OF   AVIATION  89 

that  this  one  condition  constitutes  the  basic  principle  of  flight,  and 
no  other  factor  can  be  introduced  beyond  providing  devices  for  giving 
stability  to  the  machines.  Confirmation  of  this  is  to  be  found  in 
the  fact  that  the  Eiffel  tests  have  demonstrated  that  the  best  com- 
promise between  lift  and  resistance  lies  in  a  flattened  curve  similar 
to  that  adopted  by  certain  aeroplane  makers  after  years  of  costly 
experimenting. 

Results  of  Research  in  Various  Laboratories.  It  will  be  apparent 
from  the  foregoing  that  it  is  the  precise  methods  of  the  scientist  that 
will  eventually  place  flying  on  a  successful  commercial  basis.  As  in 
all  other  branches  of  engineering,  the  theorists  and  the  physicists 
point  the  way  that  leads  the  practical  man  to  the  definite  solution  of 
perplexing  problems,  and  in  this  aviation  differs  in  no  respect  from 
any  other  art  or  science.  The  determination  of  the  fundamental 
characteristics  of  air  flow  and  air  pressure  on  different  kinds  of  sur- 
faces and  forms  has  led  without  doubt  to  a  quicker  and  surer  success 
in  actual  aeroplane  flight,  but  it  is  qualitative  rather  than  quanti- 
tative results  that  have  been  obtained  so  far.  Up  to  the  present,  few 
if  any  experiments  in  measuring  the  actual  values  of  pressures  on 
surfaces  have  been  conducted  on  full-sized  aeroplanes.  The  results 
that  have  been  obtained  come  chiefly  from  extensive  indoor  labora- 
tory experiments  conducted  on  planes  and  shapes  of  small  size,  often 
only  one-thousandth  the  size  of  the  planes  used  on  successful  machines, 
as  detailed  in  connection  -with  the  investigations  of  the  Kutchino 
and  Eiffel  laboratoriefe  just  described.  But  these  small-scale  experi- 
ments in  most  cases  have  been  performed  with  great  care  and  refine- 
ment, and  from  their  results  there  have  been  established  the  following 
empirical  and  fundamentally  important  laws  and  equations: 

(1)  The  air  pressure  on  any  plane  or  shape  varies,  within  the 
range  of  speed  used  in  flight,  substantially  as  the  square  of  the  velocity 
and  directly  as  the  size  of  the  surface.  For  the  simplest  case — a  flat 
plane  placed  normal  to  the  air  stream — the  air  pressure  P  may  be 
expressed  as 

P=KAV* 

where  A  is  the  surface  area,  V  the  velocity  of  the  moving  air  against 
the  fixed  surface,  or  conversely,  of  the  moving  surface  against  still 
air,  and  A  a  numerical  constant  or  coefficient,  the  mean  value  of 


187 


90  THEORY    OF    AVIATION 

which  may  be  taken  as  .003  when  A  is  expressed  in  square  feet  and 
V  in  miles  per  hour.  The  methods  employed  in  finding  this  and  the 
various  values  given  it  by  different  investigators  are  described  on 
pages  33-35.  This  is  an  empirical  relation,  derived  from  the  results  of 
the  numerous  experiments  in  question,  and  upon  it  is  based  practi- 
cally all  of  the  theory  of  aerodynamics  that  finds  application  in 
actual  practice. 

(2)  Air  passing  a   surface,    or   conversely,   a    surface   moving 
through  air,  causes  a  frictional  drag  on  the  surface  which  varies 
almost  as  the  square  of  the  velocity  and  directly  as  the  length  of 
the  surface. 

Many  formulas  have  been  proposed,  some  based  on  experimental 
data  and  some  on  theoretical  conclusions,  but  they  differ  widely  from 
one  another,  and  the  value  of  this  skin  friction  is  still  a  subject  of 
controversy,  many  experts  claiming  that  it  is  negligible;  many  others 
that  it  is  of  considerable  value.  Here  is  a  branch  of  aerodynamics 
still  open  to  investigation,  although  the  excellent  results  of  Professor 
Zahm's  experiments  seem  almost  conclusive  evidence  of  the  large 
value  of  frictional  resistance. 

(3)  The  pressure  on  an  inclined  flat  plane  varies  with  the  angle  of 
inclination  to  the  air  stream  but  bears  a  fixed  relation  to  the  pressure 
on  the  same  plane,  when  placed  normal  to  the  air  stream.    If  it  be 
assumed  that  P  is  normal  pressure  and  Pl  is  pressure  acting  on  a 
plane  when  it  is  inclined  below  normal,  at  an  angle  a  above  the 
horizontal,  then  this  fixed  relation  between  P  and  Pl  may  be  expressed 
as 

PI=P-  2sina 

1  +  sin2  a 

This  is  known  as  Duchemin's  formula,  and  has  been  verified 
again  and  again  by  actual  laboratory  experiments  on  small  flat 
planes,  the  Wright  Brothers  stating  that  after  having  attempted  to 
verify  all  of  the  old  formulas  they  found  in  existence  at  the  time  of 
beginning  their  experiments,  their  investigations  showed  that  this 
was  practically  the  only  one  of  its  kind  of  any  value.  A  very  simple 
approximate  relation  suggested  by  Eiffel  is  P=Pfo.  The  normal 
pressure  P  may  be  determined  for  any  plane  at  any  velocity  by  the 
relation  of  P=KAV2,  this  pressure  being  gradually  reduced  as  the 


188 


THEORY    OF    AVIATION  91 

plane    is    inclined    to   a   value   Plt   corresponding    to    that    angle 
of  inclination. 

(4)  The  pressure  on  arched  planes  is  much  greater  than  on  flat 
planes,  and  may  be  equated  to  the  value  of  the  pressure  on  a  flat 
plane  of  larger  area.    Whereas  in  inclined  flat  planes  the  pressure  Pl 
is  always  perpendicular  to  the  plane,  on  inclined  curved  planes  at 
low  angles  P±  is  inclined  in  front  of  the  perpendicular  to  the  chord 
of  the  plane.    Unlike  flat  planes,  the  pressure  on  curved  planes  can 
not  be  reduced  to  an  intelligible  formula  and,  therefore,  in  order  to 
determine  the  pressure  on  curved  planes,  resort  must  be  had  to 
tables  of  air  pressures  obtained  from  tables  of  actual  measurements 
on  test  surfaces  and  not  to  any  formulas  based  on  such  measure- 
ments.    The  pressure  Pl  on  curved  planes  is  usually  tabulated  as 
some  percentage  of  the  normal  pressure  P.    It  is  in  the  determination 
of  the  pressures  on  curved  surfaces  that  the  results  of  aerodynamical 
experiments  on  small  surfaces  have  been  of  the  greatest  value  in 
aeroplane  design.     Lilienthal,  Wright,  Prandtl,  Eiffel,  Maxim,  and 
Stanton  have  all  made  determinations  for  curved  planes  that  have 
found  wide  practical  application. 

(5)  On  curved  planes,  as  well  as  on  flat  planes,  the  total  pres- 
sure PI,  acting  on  the  plane  when  the  latter  is  inclined  at  an  angle  a 
may  be  resolved  into  a  vertical  component  L  and  a  horizontal  com- 
ponent D.    The  component  L  is  termed  the  lift  and  is  equal  to  the 
weight  of  the  aeroplane,  while  D  is  termed  the  drift  and  is  the 
dynamic  resistance  to,  motion  overcome  by  the  thrust  of  the  propeller. 

(6)  On  curved  planes,  as  the  depth  or  amount  of  curvature  or 
arching  is  increased,  the  drift  resistance  increases.     In  other  words, 
flatter  planes  have  less  resistance  than  more  highly  arched  surfaces, 
this  being  illustrated  by  the  use  of  very  flat  planes  in  high-speed 
machines.     The  experimental  results  of   Professor  Prandtl  of  Got- 
tingen  are  particularly  definite  on  this  point. 

(7)  On  curved  planes,  as  the  aspect  ratio,  or  ratio  of  span  of 
plane  to  chord,  is  increased,  the  lift  increases  greatly  for  the  same 
area.     Both  Eiffel  and  Prandtl  have  amply  verified  this,  and  it  is 
one  of  the  most  essential  points  of  successful  aeroplane  design. 

(8)  Experiments  show  that  on  a  plane  there  exists  a  point  at 
which  all  the  pressures  on  the  plane  may  be  considered  as  concen- 
trated without  disturbing  the  equilibrium.     This  center  of  action  of 


189 


92  THEORY   OF   AVIATION 

the  forces  is  termed  the  "center  of  pressure/'  On  flat  planes,  the 
center  of  pressure  moves  steadily  forward  from  the  center  of  the 
plane  to  a  point  near  the  front  edge,  as  the  plane  is  inclined  from 
the  normal  or  90-degree  position  to  zero,  or  horizontal.  On  curved 
planes  a  totally  different  action  is  observed.  The  center  of  pressure 
moves  steadily  forward  from  the  center  of  figure  to  a  point  about  one- 
third  the  width  of  the  plane  from  the  front  edge,  as  the  inclination 
is  reduced  from  90  degrees  to  15  degrees,  but  at  this  point  it  turns 
abruptly  and  moves  rapidly  to  the  rear,  passing  the  center  of  figure 
at  about  5  degrees. 

(9)  Experiments    in    aerodynamic     laboratories    have    further 
enabled  forms  of  least  resistance  to  motion  to  be  determined,  and  show 
what  kind  of  torpedo  or  fusiform  shapes  give  the  least  disturbance 
of  the  air  streams. 

(10)  Experiments  on   propellers  have  added  immensely  to  the 
knowledge  of  this  branch  of  aerodynamics,  and  have  enabled  air 
propellers   to   be   designed   that   give   a   higher   efficiency   than   is 
obtained  in  marine  practice.     The  French  propeller  manufacturing 
companies  have  had  extensive  and  elaborate  experiments  conducted 
with  full-size  propellers  and  have  used  the  results  to  great  advantage. 

(11)  The   experimental   photographing   of    the   action   of   air 
streams  on  different  planes  and  shapes  has  been  a  valuable  contribution 
to  aerodynamics  and  holds  promise  of  becoming  a  field  of  much  larger 
results  within  the  next  few  years. 

The  foregoing  are  the  fundamental  qualitative  results.  In  many 
cases,  the  values  of  different  experimenters  for  the  same  thing  show 
wide  variations.  In  determinations  of  the  constant  K,  for  example, 
as  already  referred  to  in  detail,  various  widely-differing  values  have 
been  obtained,  and  many  other  differences  are  found.  The  quanti- 
tative results  of  experiments  in  aerodynamics  are  as  yet  not  fixed, 
and  it  must  be  conceded  that  until  reliable  numerical  values  are 
obtained,  the  precise  engineering  design  that  is  looked  forward  to  is 
hardly  possible,  even  though  excellent  approximations  may  be  made. 

Methods  of  Experimenting  on  Test  Surfaces.  The  chief  sources 
of  error  or  difference  in  the  experiments  conducted  thus  far  appear  to 
be  in  the  methods  of  conducting  the  experiments  and  the  size  of  the 
planes  used.  Whether  size  of  surface  has  any  effect  on  the  nature  of 
the  pressures  or  their  unit  values  is  a  problem  in  aerodynamics  that  is 


190 


THEORY   OF   AVIATION  03 

still  to  be  solved.  Many  claim  that  the  majority  of  experiments  have 
been  conducted  on  such  small  test  surfaces  that  their  results  are  of 
little  value.  Like  all  other  aerodynamical  problems,  the  answer  is 
to  be  found  in  experiment  only.  There  are  five  different  methods  of 
conducting  experiments  on  test  surfaces  or  models.  These  are: 

(1)  Dropping  the  surface  from  a  height  in  open  air  or  a  closed 
room,  as  already  described  in  connection  with  the  work  of  the  Eiffel 
and  Kutchino  laboratories. 

(2)  Attaching  the  surface  to  a  carriage  moved  on  rails,  as  done 
by  Professor  Fraud tl  at  Frankfort;  or  sliding  down  a  long  inclined 
railway,  as  performed  by  Signor  Canovetti  in  Italy. 

(3)  Mounting  the   surface  and  testing  apparatus  on  an  auto- 
mobile and  driving  at  high  speeds,  taking  careful  record  of  the  pres- 
sures, as  employed  to  great  advantage  by  M.  Esnault  Pelterie, 
builder  of  the  R.  E.  P.  monoplane,  some  years  ago  in  France. 

(4)  By  means  of  a  whirling  table  or  large  rotating  arm  at  the 
other  end  of  which  are  carried  the  forms  or  planes  to  be  tested. 
The  first  aerodynamic  testing  apparatus,  the  old  8-foot  whirling  arm 
of  Rouse,  used  in  1758,  was  of  this  type.    Later  Lilienthal,  Mont- 
gomery, Langley,  Renard,  and  Maxim  used  it  to  determine  pressures 
on  planes,  the  action  of  the  air  in  front  of  a  plane,  and  to  test  pro- 
pellers. 

(5)  By  a  wind  tunnel,  of  which  there  are  three  principal  kinds. 
In  the  first,  used  by  Eiffel,  Prandtl,  and  Maxim,  a  huge  fan  blows 
air  into  a  restricted  passageway,  and  the  air  is  then  conducted 
through  various  screens  and  chambers  until  it  issues  past  the  test 
surfaces  in  a  more  or  less  uniform,  steady   current.    At  Gottingen, 
the  elaborate  character  of  the  air  passageway  and  screens  renders  the 
air  stream  practically  perfect  in  its  evenness  of  flow  as  it  passes  the 
test  planes.    In  the  second  type  of  wind  tunnel,  the  air  is  drawn  in 
past  the  test  surfaces  by  a  powerful  fan  placed  behind  them.    This 
is  designed  to  avoid  the  "churned"  air  that  is  exhausted  from  a  fan 
or  propeller.     Dr.  Stanton  in  England,  and  Professor  Zahm  and 
Glenn  H.  Curtiss  in  this  country,  use  wind  tunnels  of  this  type. 
The  third  type  consists  of  a  fan  blowing  air  through  a  chamber  and 
screens  as  before,  but  at  the  end  of  the  chamber  is  a  nozzle  which 
contracts  the  stream  and  greatly  increases  its  velocity.    M.  Rateau 
has  used  a  wind  tunnel  of  this  type  in  his  laboratory  at  Paris. 


191 


94  THEORY   OF   AVIATION 

Pressure  Measuring  Methods.  The  actual  devices  for  measuring 
the  pressure  vary  greatly  with  the  different  experimenters,  and  this, 
no  doubt,  plays  an  important  part  in  the  variations  observed  in  their 
results.  Pressure  gauges,  hydraulic  apparatus,  aerodynamic  balances 
of  great  sensitiveness,  pendulum  devices  capable  of  very  exact  cali- 
bration, graphic  records  on  cylinders  by  movable  pointers,  electrical 
contact  devices,  and  comparison  systems  with  standard  flat  planes, 
are  some  of  the  many  methods  employed.  To  measure  the  actual 
velocity  of  the  air  stream,  anemometers  are  employed,  arid  are  either 
of  the  rotary  cup  type  (recording  on  dials),  or  of  the  pressure  type, 
in  which  the  pressure  of  a  surface  acts  through  a  spring  and  operates 
a  large  pointer. 

Only  recently,  the  great  differences  between  conditions  of  air 
pressure  and  air  flow  inside  a  room  and  out  in  the  open  have  been 
recognized.  The  air  in  a  closed  room  is  perfectly  quiet  and  lacks  the 
characteristics  of  turbulent  motion  of  the  open  air — characteristics 
that  very  likely  have  much  to  do  with  the  pressures  on  the  surface 
of  an  aeroplane.  Although  a  simple  means  of  determining  air  pres- 
sures, the  wind  tunnel  only  slightly  approximates  flight  conditions, 
and  many  of  the  results  obtained  by  this  method  of  experiment  are 
seriously  open  to  question.  Whirling  arms  if  small  or  if  rotated  at 
too  high  a  velocity  cause  the  air  about  them  to  assume  a  rotation, 
and  thus  render  the  results  of  the  experiments  inexact.  Movement 
in  a  straight  line  in  the  open  air  is  now  recognized  as  the  best  means 
of  experiment  in  aerodynamics,  and  the  one  that  holds  the  greatest 
promise  of  establishing  fully  and  exactly  the  laws  of  flight. 

Eiffel  Experiments.  M.  Eiffel  has  already  taken  a  long  step  in 
advance  over  the  usual  form  of  experiments  with  small  test  surfaces. 
In  his  splendidly  equipped  laboratory  at  the  Champ  de  Mars,  Paris, 
he  has  made  determinations  on  reduced  reproductions  of  actual  aero- 
plane types — models  equipped  with  propellers,  motors,  and  running 
gear  built  to  an  exact  scale.  Despite  their  small  scale,  these  experi- 
ments have  proved  to  be  among  the  most  valuable  so  far  and  have 
enabled  M.  Eiffel  to  lay  down  many  more  fundamental  laws  that 
have  a  direct  and  important  bearing  on  aeroplane  design.  One  of  the 
most  interesting  facts  he  has  brought  out  is  that  when  two  identical 
planes  are  superimposed,  as  on  a  biplane,  the  lift  per  unit  of  surface 
is  less  than  if  the  same  surface  be  used  as  a  monoplane.  These  signifi- 


192 


THEORY   OF  AVIATION  95 

cant  results  show  that  as  the  distance  between  the  planes  is  increased 
from  two-thirds  to  three-thirds  and  to  four-thirds  of  the  depth,  the 
corresponding  reduction  of  unit  pressure  due  to  placing  the  two  planes 
one  over  the  other  is  65  per  cent,  70  per  cent,  and  75  per  cent,  re- 
spectively. He  has  also  made  extensive  measurements  on  model  wings 
of  eighteen  different  aeroplane  types,  making  especially  complete 
measurements  on  models  of  the  R.  E.  P.  and  Nieuport  monoplanes. 
His  investigations  on  the  distribution  of  pressure  over  a  plane 
show  definitely  that  the  pressure  at  the  front  edge  is  very  much 
higher  than  most  aeroplane  constructors  suppose,  and  that  at  the 
rear,  it  is  very  low,  often  having  a  negative  value,  i.e.,  the  air  is 
pressing  on  the  upper  surface  instead  of  the  lower. 

American  Experimental  Research.  Unfortunately,  there  are 
few,  if  any,  well-equipped  laboratories  in  this  country,  such  as  are 
to  be  found  in  Germany,  France,  and  Russia,  and  which  have  proved 
of  such  enormous  value  to  the  various  industries  of  those  countries, 
as  well  as  to  the  aeroplane  designer.  Aerodynamic  research  is 
accordingly  confined  largely  to  the  efforts  of  private  investigators 
and  to  the  aeroplane  building  companies,  very  little  having  been 
done  by  the  Smithsonian  Institution  since  Langley's  death.  Con- 
sequently, the  results  are  seldom  published,  the  companies  naturally 
employing  the  data  in  connection  with  their  own  machines. 

Curtiss  Laboratory.  Curtiss  has  established  an  aerodynamical 
laboratory  at  his  factory  in  Hammondsport,  New  York,  and  this 
will  doubtless  be  added  to  until  it  becomes  one  of  the  most  valuable 
in  the  country.  A  wind  tunnel  has  been  built  and  was  used  experi- 
mentally for  the  first  time  in  the  fall  of  1911  for  studies  of  the  stream 
lines  about  the  wings  and  body  of  the  new  Curtiss  hydroaeroplane, 
a  small  model  being  employed  for  the  purpose.  This  tunnel  is  of 
the  suction  type,  a  30-inch  electric  suction  fan  drawing  air  through 
a  screen  at  the  opposite  end,  while  windows  inserted  in  the  tube 
permit  of  observation  of  the  action  of  the  model,  smoke  being  intro- 
duced into  the  tunnel  to  make  the  action  of  the  stream  lines  of  the 
model  more  apparent.  The  air  enters  the  screen  at  a  part  of  the 
room  free  from  obstructions  and  well  above  the  floor,  a  fine  silk 
thread  suspended  in  the  current  showing  a  deviation  of  but  a  small 
fraction  of  a  degree  from  exact  parallelism  with  the  walls  of  the  tun- 
nel. Two  methods  have  been  employed  by  Curtiss  to  delineate  the 


193 


96  THEORY  OF  AVIATION 

stream  lines  of  the  air  current  flowing  past  the  model  inside  the  tube. 
One  is  the  introduction  of  smoke  already  mentioned,  and  the  other 
is  to  attach  a  silk  thread  to  a  fine  wire  and  hold  it  at  different  points 
about  the  model.  Bovth  models  show  the  flow  at  all  parts  of  the 
current  except  where  the  eddies  are  so  violent  as  to  make  the  thread 
flutter  and  the  smoke  streams  break  and  lose  their  identity.  The 
thread  is  more  convenient  to  use  than  the  smoke;  but  if  too  long 
will  not  accurately  coincide  with  the  stream  line,  owing  to  the  effect 
of  tension.  The  smoke  coincides  with  the  direction  of  flow  at  all 
points  and,  as  Professor  Marey  has  demonstrated,  may  even  indicate 
the  velocity  at  all  parts  of  the  current,  if  the  smoke  streams  be 
emitted  from  nozzles  vibrating  at  a  known  rate  transversely  to  the 
current.  In  this  case,  the  smoke  streams  are  wavy  and  show  by 
the  number  of  waves  per  inch  the  speed  of  the  current  at  the  point 
of  observation.  The  number  of  waves  per  inch  may  be  readily 
counted  on  a  photograph  of  the  model  showing  the  smoke  streams 
surrounding  it.  Indeed,  the  velocity  and  direction  of  flow  for  an 
entire  longitudinal  section  of  the  current  about  the  model  may  be 
realized  at  a  glance  from  a  photograph  of  this  kind. 

Various  methods  of  producing  satisfactory  smoke  lines  have  been 
experimented  with  by  Curtiss.  At  first,  air  was  drawn  over  the 
surface  of  ammonia  in  a  bottle,  thence  over  hydrochloric  acid  in  a 
second  bottle,  and  then  through  holes  in  a  tube  placed  across  the 
current,  but  the  vapor  thus  produced  is  pale  and  requires  good  light- 
ing in  the  dark  wind  tunnel  to  render  it  distinct  enough  for  easy 
observation  and  photographing.  The  absolute  velocity  of  the  air 
in  the  Curtiss  wind  tunnel  was  found  to  be  25  miles  per  hour  at 
the  center  of  the  current,  the  relative  velocity  at  different  parts  of  a 
section  of  the  current  being  ascertained  by  observing  the  deflection 
produced  upon  a  straight  exploring  wire  10  inches  long  suspended 
from  a  horizontal  wire  fixed  transversely  to  the  stream.  When  the 
point  of  suspension  of  the  exploring  wire  was  moved  across  the 
tunnel,  the  suspended  wire  was  deflected  less  and  less  as  it  advanced 
from  the  mid-section  toward  the  lateral  wall.  The  impact  pressure 
of  the  air  against  the  wire  is  proportional  to  its  displacement  along 
any  longitudinal  line  of  the  current.  Hence,  the  velocity  is  as  the 
square  root  of  such  displacement.  In  this  manner,  the  speed  of  the 
current  was  observed  to  decline  about  2  per  cent  from  mid-stream 


194 


THEORY  OF  AVIATION  97 

to  within  2  inches  of  the  lateral  wall,  the  tunnel  being  rectangular 
in  form,  and  not  cylindrical  as  are  those  employed  in  the  Continental 
laboratories. 

Curtiss  also  carried  out  some  very  practical  tests  in  connec- 
tion with  the  types  of  hydroaeroplane  produced  in  1911,  as  well 
as  the  regular  models.  These  included  tests  of  the  stresses  in  the 
stay  wires  of  all  the  panels  of  the  main  sustaining  surfaces  of  .the 
standard  Curtiss  biplane,  in  order  to  compare  them  with  those  deter- 
mined by  computation  and  graphical  construction.  For  this  purpose, 
the  aeroplane  was  turned  upside  down  and  supported  at  its  center. 
The  entire  main  planes  were  then  loaded  with  sand,  distributed  in 
such  a  manner  as  to  produce  in  the  guy  wires  the  same  stresses  as 
are  caused  by  flight.  When  subjected  to  full  stress,  each  wire  was 
tested  by  means  of  a  pair  of  tension  tongs.  The  jaws  of  these  tongs 
have  slots  to  pass  over  the  wire  to  be  tested  and  they  grip  it  firmly 
when  the  slots  are  closed  by  tightening  screws.  When  the  jaws 
were  thus  attached  to  a  wire  under  stress,  the  handles  of  the  tongs 
were  drawn  together  just  sufficient  to  cause  the  small  piece  of  wire 
between  the  two  points  of  attachment  to  slacken,  showing  that  it 
was  no  longer  under  stress.  The  force  acting  on  the  long  handles 
was  then  measured  by  a  spring  balance,  the  tension  in  the  wire 
being  found  directly  as  the  product  of  the  force  indicated  by  the 
spring  balance  multiplied  by  the  leverage,  i.  e.,  the  ratio  of  the 
distances  from  the  pivot  of  the  tongs  to  the  spring  balance  and  to 
the  wire  under  test.  / 

It  had  been  shown  previously  by  analysis  and  graphic  statistics, 
that  in  a  biplane  whose  surfaces  have  practically  a  uniform  running 
load  from  center  to  either  wing  tip,  as  may  be  roughly  assumed  to 
be  true  in  ordinary  practice,  the  stress  in  the  outward  and  upward- 
sloping  stays  of  the  end  panels,  or  wing  tips,  represents  but  one- 
fourth  as  much  tension  as  the  corresponding  wires  in  the  second 
panels  from  the  end,  while  those  wires  which  slope  outward  and 
downward  sustain  no  material  tension  due  to  pressure  on  the  con- 
cave side  of  the  wings,  though  they  may  be  very  severely  strained 
when  the  machine  is  jolting  over  rough  ground.  In  the  third  section 
from  either  wing  tip,  known  as  the  engine  section,  the  tension  in 
the  guy  wires  and  oblique  stay  rods  is  still  greater,  being  more  than 
five  times  the  tension  in  the  wires  of  the  end  panels. 


195 


98  THEORY   OF   AVIATION 

Though  the  tests  were  made  for  practical  rather  than  scientific 
purposes,  the  stresses  were  found  to  increase  from  the  wing  ends  to 
the  engine  section  approximately  as  indicated  by  theory.  It  was 
observed  also  that  each  wire  had  a  large  factor  of  safety,  ranging 
from  about  10  to  30.  Curtiss  then  added  his  weight  of  150  pounds 
to  one  wing  tip,  while  an  assistant  of  equal  weight  stood  on  the 
other  wing  end.  The  stress  in  the  wires  of  the  second  panel  was 
then  doubled. 

Other  tests  were  made  on  the  ribs  of  the  main  planes,  and  it 
was  noticed  that  they  were  sprung  by  the  load  of  sand  sufficiently 
to  change  the  tension  perceptibly  in  the  fore-and-aft  diagonal  wires. 
A  panel  of  the  main  planes  was  placed  upside  down  with  its  spars 
resting  on  the  trestles  placed  transversely  to  the  ribs.  When  uni- 
formly loaded  with  sand  weighing  ten  times  the  usual  pressure  on 
the  wings,  the  latter  collapsed,  due  to  breakage  of  the  ribs.  From 
these  various  tests,  it  was  concluded  that  the  weakest  part  of  the 
machine  had  a  factor  of  safety  of  ten,  i.e.,  it  would  not  give  way 
until  subjected  to  ten  times  the  stresses  usually  encountered  in 
ordinary  flight. 

In  addition  to  the  tongs  referred  to,  two  other  contrivances  were 
devised  for  testing  the  tension  of  aeroplane  wires,  one  being  an 
instrument  for  giving  the  pitch  of  the  wire  under  vibration,  while 
the  other  was  an  instrument  for  showing  the  lateral  displacement 
of  the  wire  by  a  given  force,  from  which  the  tension  could  be  read 
in  a  reference  table  or  along  a  specially-designed  index  scale,  all  of 
the  instruments  in  question  being  developed  by  Curtiss  experiment- 
ing in  collaboration  with  Dr.  Zahm. 

With  all  that  is  being  done  in  these  and  numerous  other  labora- 
tories, the  subject  has  been  scarcely  more  than  touched  upon,  though 
the  investigations  already  carried  out  have  laid  the  foundation  for 
the  scientific  construction  of  the  aeroplane.  With  the  cumulative 
data  gained  by  numerous  experimenters,  it  will  doubtless  be  possible 
in  the  course  of  comparatively  few  years  to  solve  problems  the  solu- 
tion of  which  at  present  seems  very  far  in  the  future,  and  that  other- 
wise might  never  be  definitely  settled,, 


196 


TYPES  OF  AEROPLANES 

PART  I 


STANDARD  TYPES 

General  Survey.  In  view  of  the  fact  that  aeroplane  design  can 
hardly  be  said  to  have  progressed  beyond  its  inception,  it  may  appear 
to  be  somewhat  of  a  misnomer  to  refer  to  standard  types.  There 
are,  however,  a  certain  number  of  designs  in  biplanes  and  mono- 
planes, constructed  according  to  well-defined  models,  and  after  which 
the  majority  of  others  are  patterned.  While  these  are  more  or  less 
similar  in  their  fundamental  characteristics,  they  vary  from  one 
another  in  important  details  of  size,  arrangement,  and  efficiency  of 
their  parts.  For  the  purpose  of  comparison,  a  discussion  of  their 
distinguishing  features,  as  well  as  their  merits  and  demerits,  is 
appended.  A  study  of  this  will  be  found  of  the  greatest  value  as  a 
means  of  obtaining  a  knowledge  of  the  chief  characteristics  of  the 
best-known  aeroplanes. 

The  fifteen  most  prominent  and  distinctive  types  are  described 
in  detail,  the  order  in  which  they  are  taken  up  not  being  based  on 
any  quality  of  the  machines  themselves.  The  biplanes  are  eight  in 
number,  as  follows:  (Wright,  Wright  Racer  (Baby),  Curtiss,  Voisin, 
New  Model  Voisin,  Farman,  Sommer,  and  Cody. 

The  monoplanes  are  seven  in  number,  as  follows:  Antoinette, 
Santos-Dumont,  Bleriot  XI,  Bleriot  XII,  Grade,  Pelterie,  and 
Pfitzner. 

With  few  exceptions  the  machines  in  question  as  described  in 
the  following  paragraphs  have  been  flown  thousands  of  miles  and 
used  over  extended  periods  by  a  great  number  of  aviators  and 
amateurs,  and  they  have  likewise  been  copied  in  hundreds  of  other 
machines,  but  as  the  result  of  the  experience  thus  gained,  their 
builders  have  inaugurated  various  changes,  not  merely  of  dimensions, 
but  of  construction  in  some  cases  and  of  principle  in  others.  Most 
of  these  changes  have  been  brought  about  during  1911.  In  not  a 

Copyright,  1912,  by  American  School  of  Correspondence. 


197 


2  TYPES   OF   AEROPLANES 

few  instances,  the  changes  have  been  of  sufficient  importance  to 
warrant  giving  the  new  machine  a  new  title.  Wherever  the  changes 
have  altered  the  machine  materially,  the  details  are  given  just  after 
the  description  of  the  standard  type. 

In  addition  to  the  foregoing,  there  are  some  special  types  the 
distinguishing  features  of  which  merit  reference.  Many  other  types 
of  successful  biplanes  and  monoplanes  are  in  use,  but  they  differ  so 
slightly  from  one  or  another  of  those  described  here  that  any 
detailed  mention  of  them  would  only  lead  to  confusion.  The  great 
number  of  machines  now  being  built  in  this  country  by  individual 
experimenters  or  by  manufacturers  are  either  replicas  of  those 
detailed  or  are  modifications  of  them. 

Nomenclature.  Despite  the  phenomenally  rapid  development 
of  aviation,  its  terminology  has  kept  pace  so  that  there  are  a  number 
of  expressions  the  meaning  of  which  must  be  explained  before 
attempting  a  description  of  the  machines  themselves. 

SUPPORTING  PLANE.  By  supporting  plane  is  meant  the  main  lifting 
surface  as  distinguished  from  all  auxiliary  or  stabilizing  surfaces. 

DIRECTION  AND  ELEVATION  RUDDERS.  Direction  rudder  refers  to  the 
movable,  vertical  surface  used  for  steering  to  the  right  or  left,  while  the  eleva- 
tion rudder  is  a  horizontal  surface  the  function  of  which  will  be  obvious. 

TRANSVERSE  CONTROL.  Transverse  control  is  the  device  employed  for 
the  preservation  of  lateral  balance  when  flying  straightaway  and  for  maintain- 
ing an  artificial  inclination  of  the  machine  when  rounding  turns. 

KEELS.  Keels  are  fixed  surfaces  intended  to  aid  in  the  preservation  of 
stability;  they  exert  neither  lifting  effect  nor  rudder  action. 

SPREAD.  Spread  is  the  maximum  horizontal  dimension  perpendicular 
to  the  line  of  flight. 

DEPTH.     Depth  is  the  dimension  of  the  plane  parallel  to  the  line  of  flight. 

ASPECT  RATIO.  By  "aspect  ratio"  is  meant  the  proportion  of  spread 
to  depth  and  it  constitutes  a  factor  for  defining  the  shape  of  the  supporting 
plane. 

For  the  purpose  of  more  clearly  showing  the  variation  in  size 
of  the  different  types,  detailed  and  dimensioned  plans  and  elevations 
of  each  machine  are  given.  Most  of  these  are  drawn  to  the  same 
scale,  thus  enabling  a  direct,  graphic  comparison  of  the  types. 
But  it  must  be  borne  in  mind,  inasmuch  as  aviators  are  constantly 
changing  and  rechanging  the  dimensions  of  their  machines,  without 
recording  such  alterations,  many  of  the  dimensions  given  here  are 
necessarily  approximate.  In  all  cases,  however,  the  most  recent 


198 


TYPES   OF   AEROPLANES  3 

and  accurate  data,  as  furnished  by  the  large  number  of  references 
consulted  as  well  as  by  close  personal  inspection,  has  been  employed. 

BIPLANES 

Wright.  This  Wright  machine,  Fig.  1,  is  the  original  Wright 
type  of  which  many  are  made  and  used  in  England,  France,  and 
Germany,  there  being  Wright  companies  in  those  countries  devoted 
to  their  manufacture  and  exploitation.  The  more  recent  WTright 
machines  do  not  require  a  rail  or  weight  for  starting  and  the  front 
elevation  rudder  has  been  discarded.  Among  the  biplanes  the 
Wright  is  almost  twice  as  efficient  as  any  other  type,  this  being 
ascribed  by  French  writers,  particularly  Berget,  to  the  fact  that  a 
great  deal  of  weight  is  saved  by  the  starting  device.  This  is  what 
the  latter  was  originally  adopted  for,  but  as  no  increase  in  power 
was  found  necessary  when  it  was  discarded  for  the  four-wheeled 
chassis  now  employed,  the  contention  does  not  hold  good.  In 
view  of  its  much  rougher  construction  as  compared  with  the  finely 
finished  French  machines,  its  efficiency  is  extremely  high,  owing  in 
large  measure,  doubtless,  to  the  employment  of  two  propellers 
revolving  at  a  comparatively  slow  speed. 

Frame.  Clear  spruce  and  ash  are  used  throughout  in  the  con- 
struction of  the  frame,  which  is  very  simply  but  solidly  built.  The 
bracing  wires  are  steel  and  are  made  to  fit  exactly,  while  the  struts 
or  separators  are  of  elliptical  form  with  the  small  edge  facing  the 
direction  of  motion.  (These  struts  are  equipped  with  hooks  at  each 
end  fitting  in  rings  in  the  frames  of  the  two  planes.  All  exposed 
parts  of  the  machine  are  painted  with  an  aluminum  mixture. 

Supporting  Planes.  Two  identical  and  superposed  surfaces  of 
canvas  (fine,  closely  woven  duck)  stretched  over  and  under  wood 
ribs  of  light  but  strong  built-up  construction  support  the  machine 
in  the  air.  These  surfaces,  or  planes,  are  3  inches  thick  near  the 
center  and  have  a  somewhat  flatter  and  more  regular  curve  than 
that  commonly  employed.  The  planes,  which  are  spaced  6  feet 
apart,  have  a  spread  of  41  feet,  a  depth  of  6.56  feet,  and  a  total 
area  of  538  square  feet. 

Elevation  Rudder.  In  the  Wright  biplane  the  rudder  is  so 
constructed  that  when  elevated  it  is  automatically  warped  con- 
cavely  on  the  under  side,  and  when  depressed  it  is  curved  in  the 


199 


4  .      TYPES   OF   AEROPLANES 

opposite  way.     This  materially  adds  to  the  force  exerted.     It  is 
double  surfaced,  constituting  a  small  biplane  itself  and  has  70  square 


S/DE  ELE  VAT/ON 


Fig.  1.     Original  Type  of  Wright  Biplane 


feet  of  area;    it  is  placed  well  forward  of  the  main  planes,  being 
supported  on  an  extension  of  the  landing  skids.     This  rudder  is 


200 


TYPES   OF   AEROPLANES  5 

controlled  by  a  lever  worked  by  the  operator's  left  hand.  To  rise, 
the  aviator  pulls  the  lever  toward  him.  This  motion,  transmitted 
to  the  rudder  mechanism  by  a  long,  wood  connecting  rod,  causes 
the  rudder  to  turn  upward  relative  to  the  line  of  flight  and  con- 
sequently the  machine  rises.  Reversing  the  movement  causes  it  to 
descend. 

Direction  Rudder.  The  direction  rudder  is  placed  in  the  rear 
on  the  center  line,  and  consists  of  two  identical  and  parallel  vertical 
surfaces  with  a  total  area  of  23  square  feet.  It  is  governed  by  the 
right-hand  lever,  turning  to  the  left  being  accomplished  by  pushing 
out  and  to  the  right  by  pulling  in  on  it.  The  control  is  not  employed 
exactly  in  this  manner,  however,  as  a  sidewise  movement  of  the 
same  lever  also  serves  to  warp  the  planes — a  feature  indispensable 
to  lateral  equilibrium  in  rounding  turns.  The  two  motions  of  the 
lever  are  very  intimately  connected  in  their  effect  upon  the  control. 

Transverse  Control.  Transverse  control  is  the  famous  warping 
device  invented  by  the  Wrights  for  the  preservation  of  lateral 
balance  and  for  artificial  inclination  in  making  turns,  and  is  employed 
in  a  similar  or  modified  form  in  almost  every  aeroplane  thus  far 
constructed,  the  Pfitzner  monoplane  constituting  the  most  radical 
departure  from  it.  To  permit  of  this  warping,  the  rear  vertical 
panel  of  the  main  cell,  or  double  plane,  is  divided  into  three  sec- 
tions. The  central  panel  is  solidly  braced  and  extends  on  either 
side  of  the  center  to  the  second  strut  from  each  end.  From  these 
struts,  the  rear  horizontal  crosspieces  are  merely  hinged  instead  of 
being  continued  portions  of  the  crosspiece  at  the  center,  and  the 
two  vertical  panels  on  either  end  are  not  cross  braced.  These  two 
rear  end  sections  of  the  cell  are,  therefore,  movable  vertically. 
The  entire  front  of  the  machine,  as  well  as  the  ribs  inside  the  sup- 
porting planes,  however,  are  perfectly  rigid,  there  being  no  helical 
torsion  of  the  ribs  themselves,  as  commonly  supposed.  Cables 
connect  these  two  sections  of  the  planes  together  and  lead  to  the 
right-hand  lever.  The  operation  is  as  follows:  .If  the  machine 
suddenly  tilts  or  dips  down,  at  the  right  end,  for  example,  the  lever 
is  moved  to  the  left.  This  action  pulls  down  the  rear  right  ends 
of  the  surfaces  and  at  the  same  time  pulls  the  left  ends  upward. 
An  increase  in  the  incident-  angle  of  the  outer  end  of  the  plane  on 
jthe  depressed  side  and  a  decrease  of  the  incident  angle  on  the  oppo- 


201 


6 


TYPES   OF   AEROPLANES 


site  side,  are  thus  brought  about,  righting  the  machine  at  once. 
During  this  operation,  the  entire  front  face  of  the  cell  as  well  as 
the  rear  central  section  remain  perfectly  rigid  in  every  sense. 

The  warping  apparatus  is  also  interconnected  with  the  direc- 
tion rudder  and  the  simultaneous  action  of  both  is  depended  upon. 
This  is  one  of  the  chief  claims  of  the  original  Wright  patent,  and 
in  actual  practice  the  direction  rudder  and  transverse  control  of 
the  machine  are  rarely,  if  ever,  worked  separately.  To  make  a 
turn  to  the  left,  for  example,  it  is  evident  that  if  this  same  lever 
is  moved  in  an  arc,  outward  and  to  the  left,  somewhat  similar  to 


Fig.  2.     Tail  of  Short  Wright  Biplane  Showing  Addition  of  Horizontal  Keel  at  Rear 

the  contour  of  the  desired  turn,  not  only  will  the  surfaces  -be  warped 
so  as  to  raise  the  right  end,  but  the  direction  rudder  is  also  set  to 
give  the  desired  change  of  travel,  and  the  combined  action  of  the 
two  is  prompt  and  very  effective. 

There  are  no  keels  on  the  original  Wright  biplane,  but  since 
the  elimination  of  the  forward  elevating  rudder,  these  have  been 
introduced  in  the  later  type,  Fig.  2.  In  the  older  machine,  a  small, 
pivoted,  vertical  surface  is  placed  in  front  to  indicate  any  change 
in  direction  of  the  relative  air  current. 


202 


TYPES   OF   AEROPLANES  7 

Power  Plant.  The  power  plant  consists  of  a  four-cylinder, 
vertical,  four-cycle,  water-cooled  motor  built  by  the  Wrights  them- 
selves and  rated  at  25  to  28  horse-power,  which  drives  two  double- 
bladed  propellers  in  opposite  directions  by  chains  and  sprockets. 
The  propellers  are  of  laminated  wood  construction,  made  of  clear 
spruce,  measuring  8.5  feet  in  diameter  and  having  a  9-foot  pitch. 
They  rotate  at  400  r.p.m.,  or  only  about  one  third  the  speed  at 
which  the  usual  single  propeller  is  ordinarily  driven,  and  are  placed 
at  the  rear  of  the  main  cell,  at  equal  distances  on  either  side  of 
the  center. 

Running  Gear.  As  already  mentioned,  the  original  mounting 
was  on  skids  only,  but  since  about  July,  1910,  all  of  the  Wright 


Fig.  3.     Brookins  i^  Headless  Wright  Just  About  to  Leave  the  Ground 

machines  have  been  fitted  with  four  pneumatic-tired  wheels  attached 
to  a  rectangular  frame.  The  total  weight  of  the  machine  described 
above  is  1,050  to  1,150  pounds  and  the  speed  40  miles  per  hour; 
41  pounds  are  lifted  per  horse-power  of  the  motor  and  2.05  pounds 
per  square  foot  of  supporting  surface.  The  aspect  ratio  is  6.25  to  1. 
These  figures,  however,  apply  only  to  this  particular  machine,  as  the 
Wright  biplane  built  for  the  United  States  Signal  Corps,  as  well  as 
those  constructed  by  the  Aerial  Company  of  France,  have  a  spread 
of  only  36  feet  with  a  total  supporting  surface  of  490  square 
feet. 

French  Wright.     In  the  French  Wright  machines,  the  aviator 
sits  next  to  the  motor,  and  when  instructing  Count  Lambert  and 


203 


8 


TYPES   OF   AEROPLANES 


M.  Tissandier  in  the  winter  of  1909  at  Pau,  Wilbur  Wright  had 
fitted  to  the  machine  an  extra  lever  to  control  the  elevation  rudder 
on  the  right  side  of  the  passenger  who  sat  next  to  the  motor.  The 
position  of  the  levers  for  the  passenger  was,  therefore,  the  reverse 
of  the  usual  one.  Messrs.  Tissandier  and  Lambert,  having  learned 
to  operate  in  this  manner,  have  never  changed,  but  as  they  in  turn 
have  become  the  instructors  of  many  purchasers  of  Wright  machines, 
their  pupils  are  taught  to  control  in  the  normal  manner. 

New  Model  Wright.  The  new  Wright  machine,  introduced  in 
the  summer  of  1910  and  first  seen  in  public  at  the  Asbury  Park 
Meet,  has  no  front  elevation  rudder  and  was,  therefore,  popularly 
dubbed  the  ' "headless"  Wright,  shown  in  Figs.  3  and  4.  The  eleva- 
tion of  the  machine  is  controlled  by  the  rear  horizontal  surface 

alone.  This  machine  is 
also  smaller  and  faster, 
its  spread  being  39  feet, 
depth  5.5  feet,  and  sup- 
porting surface  410 
square  feet.  With  the 
30-horse-power  motor 
employed,  the  lift  is  37 
pounds  per  horse-power, 
or  2.5  pounds  per  square 
foot  of  surface.  The 
aspect  ratio  is  7.1  to  1. 
Wright  Racer.  The 
Wright  Racer  is  officially  known  as  "Model  R"  by  the  manufac- 
turers, but  owing  to  its  diminutive  size  was  immediately  christened 
the  "Baby  Wright"  on  its  first  appearance  at  the  International 
Meet  at  Belmont  Park  in  1910.  It  was  especially  designed  for 
high  speed  and  one  of  this  model  with  an  eight-cylinder  motor 
was  entered  in  the  Gordon-Bennett  cup  race,  but  owing  to  an 
accident  it  did  not  take  part.  This  machine  is  shown  in  Fig.  5 
with  Orville  Wright  driving,  Hoxsey  holding  the  machine  on  the 
right,  and  Brookins  on  the  left.  As  the  engine  is  running,  the 
propellers  do  not  show  in  the  illustration.  Sufficient  accommoda- 
tion only  for  the  aviator  is  provided  so  that  it  is  a  one-man  ma- 
chine. It  is  said  to  be  the  fastest  climbing  aeroplane  ever  built, 


Fig.  4.     Headless  Wright  in  Flight 


204 


TYPES   OF   AEROPLANES  9 

Johnstone's  record  of  9,714  feet  made  at  Belmont  Park  having  been 
accomplished  on  this  model. 

Frame.  This  machine  is  of  the  same  headless  type  as  that 
brought  out  in  the  larger  size  during  the  early  part  of  1910.  The 
construction  of  the  frame  throughout  is  the  same  as  in  the  latter. 

Supporting  Planes.  The  supporting  planes  are  of  the  same 
design  and  construction  as  in  the  larger  machine,  but  they  have 
a  spread  of  only  26J  feet  by  a  depth  of  3  feet  7  inches,  giving  a  total 
area  of  but  slightly  over  185  square  feet.  The  length  fore  and  aft 
is  24  feet,  while  the  height  from  the  ground  to  the  top  of  the  upper 
plane  is  but  6  feet  10  inches. 

Elevation  Rudder.  The  elevation  rudder,  as  well  as  the  direc- 
tion rudder,  is  of  the  same  design,  construction,  and  operation  as  the 


\ 

Fig.  5.     Wright  Baby  Racer,  with  Orville  Wright  at  the  Wheel 

standard  Wright  flyer,  the  dimensions  merely  being  made  to  corres- 
pond to  its  smaller  size. 

Transverse  Control.  The  regular  Wright  warping  device  in 
connection  with  the  control  of  the  direction  rudder  is  employed,  as 
in  the  larger  machines. 

Power  Plant.  The  power  plant  is  an  eight-cylinder,  V-type, 
50-  to  60-horse-power  motor  which  is  characterized  by  the  same 
features  of  design  as  the  standard  Wright  four-cylinder  motor  used 
on  the  larger  machines.  It  drives  two  two-bladed  wood  propellers 
in  opposite  directions  through  the  medium  of  chains  and  sprockets, 
and,  so  far  as  may  be  noted  by  a  casual  examination,  they  are 


205 


10  TYPES   OF   AEROPLANES 

identically  the  same  as  those  employed  on  the  regular  Wright 
machines  and  are  designed  to  run  at  the  same  speed,  i.  e.,  about 
400  r.p.m.,  the  speed  of  the  motor  being  1,300  r.p.m. 

General.  The  seat  for  the  aviator  is  directly  in  front  of  and 
in  line  with  the  motor  and  there  is  no  provision  for  carrying  a  pas- 
senger, owing  to  the  extremely  small  size  of  the  machine.  It  is,  in 
fact,  a  "fly-about,"  to  coin  a  term  analogous  to  that  prevalent  in 
the  automobile  field.  The  machine  is  mounted  on  two  pairs  of 
pneumatic-tired  wheels  straddling  each  of  the  skids  and  placed 
directly  under  the  center  of  the  machine. 

The  weight  of  the  machine  alone  is  only  585  pounds,  its  total 
weight  in  flight  ranging  from  735  to  800  pounds,  thus  lifting  13.3 
pounds  per  horse-power,  taking  as  a  basis  the  maximum  weight  of 
800  pounds  and  putting  the  horse-power  of  the  motor  down  as  60. 
On  the  same  basis  of  total  weight,  the  loading  is  4.27  pounds  per 
square  foot  of  surface.  The  aspect  ratio  is  7.4  to  1. 

Wright  Model  B.  In  automobile  parlance,  this  is  the  standard 
1912  Wright  Model,  and  while  it  shows  few  or  no  departures  from 
the  principles  already  established  in  its  predecessors,  it  is  distin- 
guished by  a  number  of  refinements.  The  spread  is  39  feet  and 
the  chord  6  feet  2  inches,  the  main  planes  being  built  in  three  sec- 
tions and  covered  with  Goodyear  rubberized  fabric  in  place  of  the 
canvas  formerly  employed.  The  fabric  is  laid  diagonally  and  is 
attached  to  each  section  independently,  the  sections  being  laced 
together  when  the  machine  is  assembled.  The  main  spars  are  of 
spruce,  as  is  most  of  the  rest  of  the  woodwork,  If  X  li  inches,  the 
greatest  dimension  being  vertical  in  the  front  spar  and  horizontal 
in  the  rear  spar.  They  are  larger  in  the  middle  section  of  the  lower 
plane,  ash  being  used  in  the  rear  of  the  latter.  There  are  34 
ribs  to  each  plane,  spaced  a  foot  apart  in  the  center  and  wider 
toward  the  lateral  extremities  of  the  planes.  The  ribs  which  come 
near  struts  are  solid  between  the  main  spars,  the  others  being  built 
up  of  an  upper  and  lower  strip  with  blocks  spaced  about  six  inches 
as  distance  pieces.  The  two  ribs  that  support  the  engine  and  the 
two  seat  ribs  are  the  only  ones  between  the  spars  of  the  lower  main 
plane  in  its  center  section.  There  are  nine  pairs  of  uprights  of 
various  sizes,  the  outer  two  sets  on  each  end  being  secured  to  the 
planes  by.  the  familiar  flexible  joint,  the  remainder  having  a  form 


206 


TYPES   OF  AEROPLANES 


11 


of  socket  joint.  A  few  turnbuckles  have  made  their  appearance  in 
the  center  section,  doubtless  to  facilitate  replacement  of  the  engine 
or  other  parts.  All  the  steel  piano  wires  not  fitted  with  turnbuckles 
are  cut  to  length  and  are  interchangeable.  When  setting  up  the 
planes,  the  wires  are  attached  and  the  struts  then  sprung  into  place. 
These  guy  wires  are  cut  and  the  loop  bent  by  a  special  machine  at 
the  factory.  As  the  wire  employed  has  a  breaking  strength  of  800 


Details  of  Wright  Model  B  Combination  Warping  and  Direction  Lever 


to  2,400  pounds,  according  to  size,  there  should  be  no  occasion  for 
adjustment  on  account  of  stretch.  The  curve  of  the  planes  is  1  in 
20,  the  greatest  depth  being  two  fifths  of  the  chord  back  from  the 
front  edge.  The  aspect  ratio  is  6.25  to  1. 

The  small  semicircular  fins  or  "blinkers"  familiar  on  the  1910 
machine  have  given  place  to  two  sets  on  the  latest  machines,  due 


207 


12  TYPES   OF  AEROPLANES 

to  the  fact  that  greater  area  is  required  as  the  skids  have  been 
shortened,  thus  bringing  these  surfaces  closer  to  the  main  planes. 
Their  shape  is  that  of  small  jibs. 

The  vertical  rudder  is,  in  general,  of  the  same  construction  as 
in  the  earlier  models,  though  somewhat  smaller.  The  rudder  is 
operated  by  the  combination  warping  and  direction  lever,  Fig.  6. 
As  shown,  this  lever  also  warps  the  wings.  By  "breaking"  the  top 
section  B,  either  to  the  left  or  to  the  right  (without  moving  the 
rest  of  the  lever  from  its  position),  the  rudder  is  moved  only  to  steer 
left  or  right,  respectively.  In  making  flat  turns,  without  banking, 
the  top  section  only  of  the  lever  is  used.  The  movement  is  entirely 
a  natural  or  instinctive  one.  This  separate  movement  of  the  rudder 
is  obtained  by  having  the  sector  D,  movably  mounted,  capable  of 
individual  action  with  respect  to  lever  section  A,  through  the  steel 
tube  actuated  by  the  section  B  of  the  lever.  The  wire  which  goes 
over  the  top  of  sector  D  must  go  to  the  left  side  of  the  rudder  cross  bar. 

The  front  third  of  the  elevator  surface  is  held  rigid  while  the 
remainder  is  flexible.  This  is  operated  by  a  forward  and  backward 
movement  of  the  elevator  lever,  the  wires  being  crossed  so  that 
pushing  out  on  the  lever  steers  down  and  pulling  toward  the  operator 
causes  the  machine  to  ascend.  The  cloth  is  laid  on  diagonally  and 
only  one  surface  is  used,  the  ribs  and  spars  running  through  pockets 
in  the  cloth.  There  is  a  second  elevator  lever  which  can  be  used  by 
a  student  passenger,  who  would  then  work  the  warping  lever  (and 
rudder)  with  his  right  hand.  Some  of  the  Wright  aviators  use  the 
seat  next  to  the  engine  with  the  warping  lever  at  the  left,  while  others 
sit  on  the  outside  seat.  This  second  elevator  lever  has  a  disk 
attached,  encompassed  on  its  periphery  by  a  flat  steel  friction  band 
to  hold  the  lever  in  any  set  position. 

While  the  control  of  the  machine  does  not  appear  to  be 
instinctive,  it  certainly  is  very  easy  to  learn  and,  after  having  it 
once  impressed  upon  the  mind,  is  very  satisfactory.  It  would  seem 
that  the  exertion  of  moving  the  warping  lever  fore  and  aft  is  a 
great  deal  less  than  if  it  were  arranged  to  move  sideways  as  in  some 
other  machines.  The  warping  is  effected  by  the  lever  A,  Fig.  6. 
Pushing  forward  raises  the  left  wing  and  depresses  the  right;  the 
same  movement  turns  the  rudder  to  the  left — besides  having  a  lesser 
angle  of  incidence,  when  the  lever  as  a  whole  is  used.  The  wiring 


208 


TYPES   OF  AEROPLANES 


13 


for  the  warping  is  shown  in  the  diagrammatic  sketch,  Fig.  7.  The 
rear  spars  of  the  two  end  sections  of  the  planes  are  hinged  to  those 
of  the  center  section,  so  that  warping  may  be  accomplished  without 
flexing  the  spar.  The  lever  arrangements  have  varied  on  many  of 
the  machines.  Some  are  flown  with  the  aviator  using  the  left  hand 
for  warping.  Students  taught  by  these  use  the  right  hand  for 
warping,  as  a  rule,  and  this  is  now  the  practice  in  "breaking  in"  flyers 
in  order  that  any  passenger  or  other  weight  they  may  carry  will 
occupy  a  central  position  on  the  machine  and  retain  the  balance. 
However,  one  or  two  machines  have  been  put  out  with  two  warping 
and  two  elevating  levers,  for  those  who  desire  to  fly  together,  both 
having  learned  the  use  of  the  same  hand  for  warping. 

Referring  to  the  combination  warping  and  rudder  lever,  Fig.  6, 
the  lever  A  is  jointed  or  hinged  at  the  top.    The  short  section  B 


'  FORW4RD  G,y  LEVERS  TURNS  RUDDER  LEFT  sWD  WARPS  R/GHT 
WNGDomAMDLEFTW/M6  UP.   "BREArt/MG"S£CT/Ort  "B"  TO  LEFT 
LOWER  -SECT/ON  NORMAL,  rt//?WJ  RUDI/ER  OrtLY-TOLEFT. 


Fig.  7.     Diagrammatical  Sketch  of  Wright  Control-Mechanism 

turns  left  or  right  on  the  axis  C  for  independent  rudder  action. 
The  lever  as  a  whole  moved  forward  warps  the  left  wing  up  and  the 
right  wing  down,  at  the  same  time  turning  the  rudder  towards  the 
left,  to  offer  resistance  to  the  side  having  the  lesser  angle  of  inci- 
dence. The  elevator  is  also  warped  down  to  enable  the  machine 
to  gain  speed,  and  the  aeroplane  has  begun  to  bank,  the  right  side 
being  the  higher.  Next,  this  combination  lever  as  a  whole  is  grad- 
ually brought  back  to  normal  position,  as  the  aeroplane  is  now  at 
almost  a  forty-five  degree  angle.  At  this  stage  with  this  lever  (as 
one)  normal,  and  the  wings  straightened  out,  the  top  section  of  the 
lever  is  "broken"  over  to  the  left,  which  turns  the  rudder  only  to 
this  side.  This  operation  is  gone  through  in  making  short  circles, 
or  spirals,  for  which  the  Wright  machine  is  famous.  For  right 


209 


14  TYPES  OF  AEROPLANES 

spirals,  the  reverse  of  the  operation  just  described  must  be  carried 
out,  care  being  taken  to  straighten  out  before  the  machine .  has 
banked  at  so  steep  an  angle  as  to  make  recovery  impossible.  In 
Fig.  6  the  section  B  is  broken  to  the  left,  turning  the  rudder  only 
in  that  direction. 

The  motor  on  this  machine  does  not  differ  except  in  a  few 
details  from  that  which  the  Wright  Brothers  have  been  building  for 
their  own  machines  ever  since  they  began  flying.  One  of  the  inno- 
vations consists  of  an  emergency  shut-off  of  the  power,  consisting 
of  a  wire  conveniently  placed  over  the  aviator's  head.  Pulling  this 
raises  the  exhaust  valves  and  thus  cuts  off  the  power  of  the  motor, 
without  bringing  it  to  a  sudden  and  dead  stop,  as  in  the  case  where 
the  switch  for  short-circuiting  the  Mea  magneto  is  closed.  The 
power  can  thus  be  cut  down  considerably  without  bringing  the 
motor  to  a  stop.  The  same  method  of  feeding  the  gasoline  directly 

to  the  inlet  manifold  by  means 
of  a  gear  pump,  and  without  a 
carbureter,  is  still  retained.  As 
its  speed  increases  with  that  of 
the  engine,  the  amount  of  fuel 
fed  is  always  in  proportion  to 
the  latter's  speed.  Retarding  or 
advancing  the  spark  is  accord- 
Fig,  s.  wheel  Mounting  Details,  Wright  ingly  the  only  method  of  con- 

trolling  the  speed  of  the  motor, 

apart  from  the  exhaust  valve  control  previously  mentioned.  A 
pedal  in  front  of  the  aviator  sets  the  spark  back  to  facilitate  safe 
starting  of  the  motor,  and  the  magneto  is  provided  with  a  catch 
to  hold  it  in  the  retarded  position,  so  that  an  aviator  may  start 
his  own  machine  without  danger  of  having  it  run  away  from  him 
before  he  can  get  into  the  seat.  The  weight  of  the  bare  engine  is 
180  pounds  and  it  consumes  about  4  gallons  of  gasoline  per  hour, 
the  12-gallon  tank  accordingly  providing  sufficient  for  a  three-hour 
flight. 

The  engine  is  mounted  at  either  end  of  the  base  on  cross  mem- 
bers, which  in  turn  rest  on  the  solid  engine  foundation  ribs.  Dupli- 
cate sprockets,  which  are  screwed  and  locked  to  the  crank  shaft 
back  of  the  flywheel,  drive  by  means  of  special  roller  chains  the 


210 


•4/M  z'-o  -\ 


Fig.  9.     Detailed  Diagrams  of  Wright  Model  B 


16 


TYPES   OF   AEROPLANES 


fffOHT  ELCVAT/OH 


Fig.  10.     Detailed  Diagram  of  Curtiss  Biplane 


212 


TYPES   OF   AEROPLANES 


17 


two  propellers,  their  speed  being  geared  down  in  the  ratio  of  11  to 
34.     At   an  engine  speed  of    1,325  r.p.m.,  the   propellers  turn  at 


Fig.  11.     Curtiss  on  His  Trip  from  Albany  to  New  York  City.     Leaving  Poughkeepsie 

428  r.p.m.,  giving  a  flying  thrust  of  about  250  pounds.     Adjust- 
able stays  are  provided  for  tightening  the  chains. 


213 


18 


TYPES   OF   AEROPLANES 


For  the  landing  gear,  wheels  are  used  in  combination  with  the 
usual  skid  arrangement,  the  skids  themselves  having  been  very  much 
shortened.  The  method  of  mounting  the  wheels  is  illustrated  in 
Fig.  8.  The  complete  machine  is  illustrated  in  Fig.  9. 

With  operator  and  passenger,  ready  to  fly,  the  machine  weighs 
about  1,250  pounds.  The  wreight  thus  carried  per  horse-power  is 
about  40  pounds,  while  the  loading  on  the  above  basis  figures  out 
at  but  2|  pounds  per  square  foot.  Lancaster  gives  the  Wright 
machine  an  efficiency  of  63  per  cent,  after  deducting  5  per  cent  for 
loss  in  the  chains.  In  a  book  by  Eiffel  (1911),  it  is  stated  that  30 


Fi  g.  12.     Curtiss  on  His  Albany  to  New  York  Trip.     Flying  Down  the  Hudson 

horse-power  is  required  to  fly  the  Wright  machine,  which,  in  view 
of  the  facts,  is  obviously  an  erroneous  conclusion. 

Curtiss.  The  Curtiss  biplane,  Fig.  10,  embodies  in  its  construc- 
tion several  features  that  distinguished  the  aeroplanes  built  by  the 
Aerial  Experiment  Association,  of  which  Glenn  H.  Curtiss  was  a 
member.  The  first  flight  of  this  type  was  made  in  June,  1909.  At 
Rheims,  France,  in  August  of  the  same  year,  this  miniature  biplane 
captured  the  Gordon-Bennett  trophy  as  well  as  several  other  prizes, 
under  the  able  guidance  of  Curtiss.  A  number  of  these  machines 


814 


TYPES   OF   AEROPLANES 


19 


are  being  flown  and  have  a  great  many  estimable  performances  to 

their  credit,  such  as  the  flight  of  Curtiss  from  Albany  to  New  York, 

illustrated  in  Figs.   11,   12,  and 

13,  and  Ely's  flight  from  the  deck 

of  a  man-of-war  to  the  shore  and 

back.     The  Curtiss  is  one  of  the 

fastest  biplanes  in  use. 

Frame.  The  main  cell  and 
smaller  parts  are  made  of  ash 
and  spruce,  while  the  long  out- 
riggers are  of  bamboo,  several  of 
the  members  of  the  frame  meet- 
ing at  the  front  wheel  of  the  land- 
ing chassis.  Small  steel  cables  and 
wires  are  employed  for  bracing. 

Supporting  Planes.  The  sup- 
porting planes  consist  of  two  iden- 
tical directly-superposed  surfaces 
made  of  one  layer  each  of  Bald- 
win rubber  silk  tacked  to  spruce 
ribs  and  laced  to  the  frame,  and 
are  of  highly-finished  construc- 
tion. A  distance  of  5  feet  sepa- 
rates the  two  surfaces.  Their 
spread  is  26.42  feefy  depth  4.5 
feet,  and  total  area  220  square 
feet. 

Elevation  Rudder.  The  ele- 
vation rudder  is  a  small  biplane 
cell  having  two  similar  surfaces 
of  a  total  area  of  24  square  feet 
and  mounted  on  bamboo  outrig- 
gers on  the  meeting  point  of  which 
it  is  pivoted,  Fig.  14.  It  is  con- 
trolled by  a  long,  bamboo  pole 
attached  to  the  stanchion  on  which  the  steering  wheel  is  mounted. 
To  descend,  the  operator  pushes  out  on  the  wheel,  and  to  ascend 
draws  it  toward  him.  In  Fig.  14,  Curtiss  is  shown  at  the  wheel. 


Fig.  13.     Curtiss  Rounding  the  Statue 
of  Liberty 


20 


TYPES   OF   AEROPLANES 


Direction  Rudder.  For  steering  to  right  or  left,  a  single,  vertical 
surface  of  6.6  square  feet  of  area  is  pivoted  at  the  meeting  point 
of  a  similar  pair  of  bamboo  outriggers  extending  to  the  rear.  It  is 
operated  from  the  steering  wheel  by  cables  running  through  the 
hollow  outriggers. 

Transverse  Control.  Transverse  control  consists  of  two  inde- 
pendent balancing  planes,  or  ailerons,  of  12  square  feet  area  each, 
which  are  shown  very  clearly  in  Fig.  15.  They  are  placed  at  each 
end  of  the  main  cell  and  are  pivoted  midway  between  the  upper 
and  lower  main  planes.  They  are  designed  to  preserve  the  lateral 
balance  and  are  tipped  inversely  by  means  of  a  brace  fitted  to  the 


Fig.  14.     Elevation  Rudder  and  Steering  Gear  on  Curtiss  Machine 

aviator's  shoulders  and  controlled  by  the  movement  of  his  body. 
If  the  machine  is  depressed  on  the  left  side,  the  aviator  leans  to 
the  right  and  in  doing  so  shifts  the  brace,  causing  the  aileron  on  the 
left  side  to  turn  down  and  the  one  on  the  right  to  turn  up,  the  two 
being  interconnected  by  cables,  thus  righting  the  machine.  By 
"turning  down"  in  this  connection  is  meant  a  motion  relative  to  the 
axis  of  the  aileron  itself  and  not  to  the  line  of  flight.  In  other 
words,  it  swings  on  its  supporting  shaft.  When  turned  down,  its 
incidence,  i.  e.,  the  angle  it  makes  with  the  line  of  flight,  is  positive 


216 


TYPES   OF   AEROPLANES 


21 


and  it  therefore  exerts  a  greater  lifting  force.  When  making  a  turn 
to  the  right,  for  instance,  the  aviator  by  leaning  to  the  right,  thus 
causing  the  left  end  to  lift,  can  make  a  much  sharper  turn  than 
with  the  use  of  the  direction  rudder  alone,  while  the  lateral  balance 
is  also  preserved. 

Keel.  A  horizontal  fixed  surface,  or  keel,  is  placed  in  the  rear 
and  has  an  important  steadying  effect.  Its  area  is  15  square  feet. 
A  small,  triangular  vertical  plane  is  sometimes  placed  in  front  and 
aids  in  turning. 

Power  Plant.  In  the  original  machine  the  power  plant  consisted 
of  a  four-cylinder,  vertical,  four-cycle,  air-cooled^  motor  of  25  horse- 
power, placed  well  up  between  the  two  main  planes  at  the  rear.  It 
drives  a  two-bladed  wood  propeller  direct  at  1,200  r.  p.  m.  The 


Fig.  15.    Curtiss  Machine  in  Flight,  Showing  Aih 


id  Position  of  Operator 


propeller  has  a  diameter  of  6  feet  and  a  pitch  of  5  feet.  In  more 
recent  Curtiss  machines,  an  eight-cylinder,  V-type,  four-cycle,  air- 
cooled  motor  of  50  horse-power  is  employed. 

General.  The  seat  for  the  aviator  is  on  the  framing  in  front  of 
the  main  .cell  and  in  line  with  the  motor,  Fig.  15.  When  a  passenger 
is  carried,  a  seat  is  provided  at  one  side  and  somewhat  below  the 
aviator.  The  machine  runs  on  three  pneumatic-tired  wheels,  rigidly 
fixed  to  the  frame,  no  springs  being  provided.  The  total  weight  is 
from  530  to  570  pounds,  and  the  speed  is  47  m.  p.  h.;  22  pounds 
are  lifted  per  horse-power,  and  2.5  pounds  per  square  foot  of  sur- 
face. The  aspect  ratio  is  5.65  to  1. 

During  1910,  Willard,  one  of  the  Curtiss  aviators,  employed  a 


217 


22  TYPES   OF   AEROPLANES 

much  larger  machine  of  exactly  the  same  type,  in  which  he  succeeded 
in  carrying  three  passengers  besides  himself.  The  supporting  planes 
of  this  machine  have  a  spread  of  32  feet,  a  depth  of  5  feet,  and  a 
total  area  of  316  square  feet.  The  elevation  rudder  is  31  square  feet 
in  area,  and  the  direction  rudder  7.5  square  feet,  while  the  rear 
horizontal  keel  has  an  area  of  17.5  square  feet  and  the  ailerons  are 
each  of  27  square  feet  area.  A  Curtiss  eight-cylinder,  50-horse- 
power  motor  is  employed  to  directly  drive  a  7-foot  propeller  at 
1,100  r.  p.  m.  The  maximum  total  weight  in  flight  is  1,150  pounds, 
thus  lifting  22.6  pounds  per  horse-power,  and  3.64  pounds  per  square 
foot  of  surface.  The  aspect  ratio  is  6.4  to  1.  It  was  in  a  machine 
of  this  type  that  Curtiss  made  his  flight  from  Albany  to  New  York. 

At  the  International  Meet  at  Belmont  Park,  New  York,  in 
October,  1910,  Curtiss  exhibited  a  radically  different  type  of  machine. 
(See  Fig.  49.)  This  embodied  most  of  the  constructional  features 
already  described,  but  instead  of  two  similar  planes  there  was  one 
very  large  main  surface  with  an  extremely  small  superposed  plane 
directly  above  the  center  of  the  latter.  Though  termed  a  biplane, 
it  was  practically  a  monoplane  in  everything  but  name.  No  oppor- 
tunity was  afforded  of  seeing  what  it  could  do  in  flight. 

In  a  later  type  of  the  Curtiss,  the  ailerons  are  pivoted  from 
the  rear  struts  instead  of  the  front  ones,  this  doing  away  with  their 
interference  of  the  lifting  power  of  the  upper  main  plane.  Head 
resistance  has  been  cut  down  by  double  surfacing  the  planes,  thus 
enclosing  the  ribs  and  beams,  and  also  by  adopting  a  single  surface 
in  place  of  the  former  biplane  elevator.  The  axis  of  the  new  elevator 
is  placed  only  6  feet  9  inches  in  front  of  the  main  planes  and  has 
two  short  stays  of  bamboo  between  the  wheel  and  the  elevator 
instead  of  the  elaborate  and  complicated  structure  formerly  employed 
for  staying.  The  rear  tail  flaps  work  in  conjunction  with  the  elevator, 
being  pivoted  at  a  point  about  13  feet  to  the  rear  of  the  main 
planes.  Two  triangular  stabilizing  fins  are  used  instead  of  the  usual 
plane,  their  angle  of  incidence  being  about  2  degrees,  which  can 
readily  be  changed.  The  vertical  rudder  is  placed  between  these 
two  flaps  and  is  pivoted  back  of  its  front  edge,  and  it  is  operated  by 
a  tiller  post  or  forward  extension,  instead  of  attaching  the  cables 
directly  to  the  rudder  itself.  The  span  is  30  feet,  chord  4  feet  2 
inches,  and  the  planes  are  4  feet  5  inches  apart  vertically,  the 


218 


TYPES   OF   AEROPLANES 


23 


camber  apparently  not  having  been  changed.  The  dimensions  of 
the  front  elevator  are  2  feet  X  6  feet  3 J  inches,  with  a  triangular 
vertical  fin  attached  to  it  above.  A  standard  eight-cylinder,  V-type, 
50-horse-power  motor  of  Curtiss  make  drives  a  Curtiss  two-bladed 
propeller,  the  laminated  engine  base  being  supported  at  the  rear  by 
steel  tubing,  which  is  also  used  to  brace  the  entire  rear  section.  In 
front,  the  base  is  bolted  to  two  short  laminated  struts.  The  height 
of  the  base  is  14  inches,  and  above  this  a  triangle  of  1-inch  oval  steel 
tubing  extends  to  the  top  plane,  where  it  is  secured  by  a  bolt.  The 


Fig.  16.     Delagrange  Model  of  Voisin  Biplane 

engine  is  placed  9  inches  rearward  from  the  rear  beam,  and  the 
canvas  seat  is  8  inches  forward  of  the  front  beam. 

Voisin.  The  Voisin  Brothers  began  their  activity  as  constructors 
of  aeroplanes  as  early  as  1905,  when  they  built  gliders  for  both 
M.  Archdeacon  and  M.  Bleriot.  These  gliders  were  successfully 
operated  over  the  Seine,  being  lifted  from  the  surface  of  the  river 
and  towed  at  high  speed  by  motorboats.  In  1906,  they  built  a 
power-driven  machine  after  the  designs  of  the  late  M.  Delagrange, 
Fig.  16,  and  subsequently,  after  making  a  few  changes  in  the  design, 


219 


24 


TYPES   OF  AEROPLANES 


built  a  machine  for  Henri  Farman,  Fig.  17,  which  was  the  first 
successful  aeroplane  of  European  manufacture.  Since  that  time,  the 
design  of  this  type  has  remained  substantially  the  same,  except  for 
the  addition  of  several  keels,  Fig.  18.  The  Voisin  biplane  has  been 
largely  used  abroad,  over  one  hundred  machines  of  this  type  having 
been  built. 

Frame.    The  frame  is  made  of  ash  with  steel  joints  and  several 
parts  of  steel  tubing.     It  consists  essentially  of  a  large  box-cell 


Fig.  17.     Henri  Farman  in  an  Early  Type  of  Voisin  Biplane 

mounted  on  a  central  chassis,  while  attached  to  it  some  distance  in 
the  rear  is  a  smaller  box-cell  of  the  same  form.  This  central  chassis 
is  really  a  unit  in  itself,  carrying  the  wheels,  the  motor,  the  aviator's 
seat,  and  at  the  front  the  elevation  rudder. 

Supporting  Planes.  Two  main  supporting  planes  of  similar 
dimensions  and  directly  superposed  are  employed,  the  surfaces 
consisting  of  continental  cloth  (a  cotton  and  rubber  fabric)  stretched 


220 


S/DE  £LEVAT/OM 


FLAN 


fffOMT  ELEVAT/ON. 

Fig.  18.     Voisin  Biplane  with  Vertical  Keels 


221 


26  TYPES   OF  AEROPLANES 

over  ash  ribs.  Their  form  is  rectangular.  The  spread  is  37.8  feet, 
the  depth  6.56  feet,  and  the  total  area  496  feet. 

Direction  Rudder.  A  single  surface  of  25  square  feet  area, 
placed  in  the  center  of  the  rear  cells,  is  used  for  directing  the  machine. 
It  is  operated  by  means  of  a  steering  wheel  and  cables  similar  to 
those  on  a  boat. 

Elevation  Rudder.  The  elevation  rudder  consists  of  a  single 
surface  of  41  square  feet  area  situated  at  the  forward  end  of  the 
central  chassis,  and  is  controlled  by  a  lever  system  attached  to  the 
axis  of  the  steering  wheel.  By  pushing  out  on  the  steering  wheel, 
the  rudder's  inclination  with  the  line  of  flight  is  reduced  and  the 
machine  descends,  the  reverse  action  being  obtained  by  pulling  in. 
There  is  no  operating  mechanism  employed  for  transverse  control 
in  the  earlier  Voisin  machines,  lateral  stability  being  attained  by 
the  use  of  a  number  of  keels  which  took  the  form  of  vertical  parti- 
tions at  regular  intervals  between  the  main  planes,  thus  dividing 
the  machine  into  a  number  of  cells.  This  has  recently  been  aban- 
doned, however,  in  favor  of  the  system  of  independent  ailerons. 

Power  Plant.  A  50-  to  55-horse-power  motor,  placed  on  the 
rear  of  the  central  chassis  and  back  of  the  main  planes,  drives  a 
two-bladed  metal  propeller  direct  at  a  speed  of  1,200  r.  p.  m.,  the 
propeller  measuring  7.6  feet  in  diameter  with  a  pitch  of  4.6  feet. 
Several  types  of  motors  have  been  used. 

General.  The  aviator's  seat  is  placed  on  the  central  chassis  in 
front  of  the  motor  and  just  back  of  the  forward  edge  of  the  main 
planes.  As  a  starting  and  landing  chassis,  two  large  pneumatic-tired 
wheels  fitted  with  coil  spring  shock  absorbers  are  fitted  at  the  front 
and  two  at  the  rear.  To  avoid  disastrous  results,  should  the  machine 
land  at  too  sharp  an  angle,  head-on,  a  small  wheel  is  fitted  to  the 
front  end  of  the  chassis  directly  beneath  the  elevating  rudder.  The 
total  weight  is  from  1,100  to  1,250  pounds,  speed  35  m.  p.  h.;  23 
pounds  are  lifted  per  horse-power,  and  2.37  pounds  per  square  foot 
of  surface.  The  aspect  ratio  is  5.75  to  1.  The  use  of  the  six  vertical 
planes  (two  vertical  walls  of  the  rear  cell  and  four  vertical  partitions 
between  the  two  main  supporting  planes),  Fig.  18,  for  steadying  the 
machine  transversely  and  keeping  it  to  its  course,  are  much  lauded 
by  Berget  as  superior  to  the  Wright  system  of  warping  the  planes, 
but  experience  appears  to  have  proved  to  the  contrary. 


222 


TYPES   OF   AEROPLANES 


27 


The  Voisin  type  of  biplane  has  recently  been  modified  as  follows: 
The  vertical  partitions  have  been  done  away  with  and  ailerons  are 
employed,  together  with  a  single  plane,  horizontal  keel  at  the  rear, 
instead  of  two  planes.  A  60-horse-power  E.  N.  V.  motor  is  employed, 
the  total  weight  of  the  machine  being  about  1,170  pounds,  giving  a 
lift  of  19.5  pounds  per  horse-power,  and  3.27  pounds  per  square  foot 
of  surface.  The  aspect  ratio  is  5.13  to  1.  This  is  a  racing  type  of 
Voisin  and  is  characterized  by  the  elimination  of  most  of  the  struts, 
cross  wires,  and  other  parts  tending  to  increase  the  resistance  to 
flight. 

The  regular  Voisin  biplane  also  has  been  altered  by  discarding 
the  vertical  partitions  altogether,  the  design  otherwise  remaining  the 


Fig.  19.     Voisin  Biplane  in  which  Paris-Bordeaux  Flight  was  Made 

same.  This  machine  has  a  spread  of  36.1  feet,  a  depth  of  6.56  feet, 
a  total  area  of  430  square  feet,  and  a  weight  of  1,350  pounds.  The 
motor  employed  is  an  eight-cylinder  E.  X.  V.  of  60  horse-power, 
carrying  22.5  pounds  per  horse-power  and  3.14  pounds  per  square 
foot  of  surface.  The  aspect  ratio  is  5.5  to  1.  In  some  of  the  more 
recent  Voisin  machines  the  front  elevating  rudder  also  has  been  dis- 
carded, Fig.  19. 

Voisin  Tractor  Screw.  This  machine,  Fig.  20,  was  first  built 
in  the  latter  part  of  1909,  and  embodies  several  totally  new  departures 
in  the  construction  of  biplanes.  It  did  not  meet  with  particular 


223 


28 


TYPES   OF   AEROPLANES 


PLAN 


X 


/-  \ 


O     f    £    3    4-     S    6     7    8    3    10  tf  JZ 
3CALE  OF  FEET 


FftOMT 


Fig.  20.     Voisin  Tractor  Screw  Type 


224 


TYPES   OF   AEROPLANES  29 

success  during  1910,  although  the  Goupy  and  Breguet  aeroplanes  of 
the  same  type  have  been  flown  with  great  ease. 

Frame.  In  this  instance,  the  central  chassis  is  extended  a  Con- 
siderable distance  to  the  rear,  forming  an  "appendage."  At  the 
front  are  situated  the  motor  and  propeller,  while  directly  behind  the 
propeller  is  the  main  cell,  with  an  auxiliary  cell  at  the  extreme  rear. 
Ash,  steel  joints,  and  steel  tubing  are  used  throughout. 

Supporting  Planes.  The  supporting  planes  are  two  similar, 
directly-superposed  surfaces  with  a  spread  of  37  feet,  a  depth  of  5 
feet,  and  an  area  of  370  square  feet.  By  comparing  the  side  eleva- 
tions of  the  Voisin  and  Wright  machines,  the  slight  difference  in  the 
curvature  of  the  planes,  as  well  as  their  thickness,  will  be  noted, 
though  on  comparing  this  feature  in  all  of  the  machines  illustrated, 
their  striking  similarity,  as  well  as  their  close  adherence  to  the  pisci- 
form  contour  of  the  plane — laid  down  by  Colonel  Renard  as  the 
most  efficient  shape  for  speed  and  stability — will  be  at  once  apparent. 

Direction  and  Elevation  Rudder.  As  these  two  elements  are 
combined  in  the  actual  construction,  they  are  accordingly  described 
together.  They  are  formed  by  the  rear  cell,  consisting  of  two  hori- 
zontal surfaces  of  about  80  square  feet  of  area,  and  two  vertical 
surfaces  of  about  50  square  feet,  the  entire  cell  being  pivoted  on  a 
universal  joint  so  that  it  may  be  moved  in  any  direction.  The 
movement  of  the  cell  is  controlled  by  cables  leading  to  a  large 
steering  wheel  in  front  of  the  aviator,  the  horizontal  surfaces  acting 
to  elevate  or  depress  ^he  machine,  and  the  vertical  surfaces  to  change 
the  direction  of  its  travel.  To  ascend,  the  inclination  of  the  cell 
relative  to  the  line  of  flight  is  decreased,  the  leverage  desired  being 
the  opposite  of  that  necessary  with  a  front  elevation  rudder.  Four 
vertical  partitions  are  placed  between  the  main  planes.  There  is  no 
transverse  control. 

Power  Plant.  The  power  plant  consists  of  a  40-horse-power,  four- 
cylinder  Voisin  motor  placed  at  the  front  end  of  the  chassis  and  carry- 
ing directly  on  its  crank  shaft  a  two-bladed  metal  propeller  7.2  feet 
in  diameter  with  a  4-foot  pitch,  which  it  drives  at  1,300  r.  p.  m. 

General.  The  chassis  is  mounted  on  two  large  pneumatic-tired 
wheels  forward,  fitted  with  shock-absorbing  springs,  and  a  smaller 
third  wheel  at  the  rear,  while  the  aviator's  seat  is  placed  on  the 
central  frame  at  the  rear  of  the  main  cell.  The  total  weight  is  from 


225 


30 


TYPES   OF   AEROPLANES 


fffOMT  ELEYAT/ON  _ 

Fig.  21.     Details  of  Farman  III  Biplane 


226 


TYPES   OF   AEROPLANES  31 

800  to  950  pounds  and  the  speed  is  said  to  be  50  miles  an  hour; 
19  pounds  per  horse-power  are  lifted  and  2.36  pounds  carried  per 
square  foot  of  surface.  The  aspect  ratio  is  7.4  to  1. 

Farman.  The  Farman  machine,  Fig.  21,  has  figured  very 
prominently  in  the  making  of  records  and  the  winning  of  prizes, 
having  been  employed  extensively  by  such  aviators  as  Paulhan  and 
White,  as  well  as  by  Farman  himself,  Fig.  22.  More  than  a  hundred 
of  the  Farman  biplanes  had  been  built  and  put  into  .use  up  to  the 
end  of  1910.  It  is  a  comparatively  heavy  type,  and  for  a  slow- 
moving,  reliable  machine  it  has  proved  very  satisfactory. 

Frame.  The  frame  consists  essentially  of  a  main  box-cell, 
somewhat  similar  in  design  to  a  Pratt  truss,  counterbalanced  through- 
out with  identical  upper  and  lower  chords,  uprights  of  wood  acting 
as  compression  members  and  cross  wires  as  tension  members,  as  is 
the  case  in  all  of  the  biplanes  considered  in  this  description  of 
standard  types.  The  supporting  surfaces  are  analogous  to  the  upper 
and  lower  decks  of  such  a  truss. 

Supporting  Planes.  These  supporting  planes  are  practically 
identical  with  those  of  the'  machines  already  described,  the  surfaces 
themselves  being  made  of  continental  cloth,  stretched  tightly  over 
ash  ribs.  Their  spread  is  33  feet,  depth  6.6  feet,  and  total  area  430 
square  feet.  The  distance  between  the  planes  is  6.6  feet,  which 
causes  the  machine  to  appear  very  much  larger  than  the  others  by 
comparison  and  also  gives  it  a  very  cumbrous  look,  the  latter  being 
accentuated  by  its  very  deliberate  flight. 

Elevation  Rudder.  The  elevation  rudder  consists  of  -a  single, 
horizontal  surface  having  an  area  of  43  square  feet  and  is  placed 
well  out  in  front.  It  is  hinged  and  braced  to  two  sets  of  outriggers, 
firmly  attached  to  the  main  cell,  and  is  controlled  by  a  large  lever 
at  the  aviator's  right  hand.  By  pulling  on  this  lever,  the  rudder  is 
tilted  upward  and  the  machine  rises,  the  method  of  control  being 
almost  instinctive  and  very  easily  acquired. 

Direction  Rudder.  Two  equal  surfaces  vertically  placed,  of  an 
aggregate  area  of  30  feet,  serve  to  control  the  travel  of  the  machine. 
These  surfaces  move  together  and  are  operated  by  a  pivoted  lever 
on  which  the  aviator  rests  his  feet.  By  pressing  so  as  to  turn  the 
lever  to  the  left  the  machine  alters  its  course  in  the  same  direction, 
the  movement  being  transmitted  to  the  rudder  itself  by  cables. 


227 


32  TYPES   OF   AEROPLANES 

Transverse  Control.  The  control  of  the  lateral  equilibrium,  i.  e., 
the  tipping  from  side  to  side,  is  effected  by  the  use  of  ailerons  or 
"wing  tips"  consisting  of  four  flaps  constituting  the  rear  ends  of 
each  plane.  The  operation  of  these  wing  tips  is  brought  about 
simultaneously  with  that  of  the  direction  rudder  through  an  arrange- 
ment identical  with  that  on  the  Wright  biplane,  i.  e.,  a  lever  which 
may  be  moved  in  any  direction,  its  forward  and  back  motion  actuating 
the  rudder,  while  a  sidewise  movement  operates  the  wing  tips,  from 
which  it  will  be  apparent  that  they  are  merely  a  modification  of 
the  Wright  idea.  This  lever  is  connected  by  wires  to  the  lower  flap 
on  each  side  and  they  are  interconnected  in  the  same  manner  with 
the  flaps  above  them.  When  the  machine  is  standing  still  the  flaps 
merely  hang  loose  and  the  wires  relax,  but  when  in  flight  the  wind 
keeps  them  out  and  the  wires  are  taut  so  that  they  may-  be  con- 
trolled by  the  lever.  The  extra  resistance  these  flaps  or  ailerons 
create  is  probably  responsible  in  large  measure  for  the  decreased 
speed  of  the  machine. 

Keels.  Two  horizontal  surfaces  at  the  rear  act  as  keels.  Their 
combined  area  is  about  80  feet,  but  as  their  angle  of  incidence  is  low 
the  lift  they  exert  is  small,  their  only  function  being  to  steady  the 
machine  longitudinally. 

Power  Plant.  The  power  plant  consists  of  a  50-horse-power, 
seven-cylinder,  air-cooled,  rotary  Gnome  motor,  mounted  on  a  shaft  at 
the  rear  of  the  lower  plane.  A  two-bladed  wood  propeller  of  8.5 
feet  in  diameter  by  a  4.62-foot  pitch  is  attached  directly  to  it  and 
revolves  with  the  motor  at  a  speed  of  1,200  r.  p.  m. 

General.  The  machine  is  mounted  on  two  long  skids  forming 
part  of  the  framework,  similar  to  the  Wright  construction,  and  upon 
each  of  these  skids  is  placed  a  pair  of  wheels.  The  latter  are  attached 
to  rubber  springs  so  that  in  starting  the  machine  runs  on  them,  but 
in  alighting  they  give  way,  permitting  it  to  slide  on  the  skids.  The 
total  weight  is  from  1,100  to  1,350  pounds,  the  variation  in  this,  as 
in  every  instance,  being  accounted  for  by  the  fact  that  it  includes 
that  of  the  aviator.  The  Weight  lifted  per  horse-power  is  24  pounds, 
and  2.8  pounds  per  square  foot  of  surface,  while  the  speed  is  37 
miles  per  hour.  The  aspect  ratio  is  5  to  1. 

New  Models.  In  the  foregoing,  a  description  has  been  given 
of  the  original  type  of  Farman  biplane,  numerous  modifications 


338 


TYPES   OF   AEROPLANES 


33 


Fig.  22.     Farman  Biplane  in  Flight 


229 


34  TYPES   OF   AEROPLANES 

having  been  made  in  more  recent  machines,  Fig.  22.  The  latter,  for 
instance,  are  fitted  with  a  single-surface  direction  rudder,  instead  of 
the  twin  surfaces  mentioned.  The  elevation  rudder  is  kept  in  front, 
but  is  made  smaller,  and  in  addition  the  rear  end  of  the  upper  of 
the  two  fixed,  horizontal  keels  at  the  rear  is  made  movable  con- 
jointly with  the  front  rudder  to  control  the  elevation  of  the  machine. 
In  some  cases,  only  a  single  surface  is  used  at  the  rear.  One  wheel 
has  been  substituted  for  the  two  formerly  employed,  the  other  char- 
acteristics of  the  machine  remaining  substantially  as  described. 

The  new  racing  Farman  biplane  is  distinguished  by  the  following 
features:  The  spread  is  reduced  to  28  feet  and  the  area  to  350 
square  feet,  while  the  total  weight  in  flight  is  about  1,050  pounds. 
The  lift  is  21  pounds  per  horse-power,  while  that  per  square  foot  is 
the  unusually  high  figure  of  3  pounds.  The  aspect  ratio  is  4.2  to  1. 

Another  more  recent  type  of  Farman  is  the  huge,  new  passenger- 
carrying  machine  which  made  the  first  four-passenger  record.  This  has 
a  spread  of  47.6  feet  and  an  area  of  approximately  540  square  feet. 
The  maximum  total  weight  is  nearly  1,750  pounds,  or  close  to  a  ton, 
thus  giving  a  capacity  of  34  pounds  per  horse-power  and  a  loading  of 
3.15  pounds  per  square  foot  of  surface.  The  aspect  ratio  is  7.1  to  1. 

In  a  still  later  type  of  the  Farman,  the  ailerons  are  let  into  the 
wings  and  while  they  are  hinged  they  are  not  permitted  to  hang 
down,  as  was  formerly  the  case,  this  innovation  being  responsible 
for  a  decided  reduction  in  the  head  resistance.  Another  type, 
brought  out  at  the  end  of  1911,  shows  an  entirely  new  form  of  stabil- 
izing surfaces.  These  take  the  form  of  two  pairs  of  long  planes, 
one  at  each  end  of  the  main  planes,  and  with  their  narrow  edge  to 
the  wind,  giving  them  a  very  small  aspect  ratio,  though  they  have 
a  comparatively  large  area.  Each  pair  is  held  apart  by  struts  and 
they  are  mounted  on  a  vertical  shaft,  which  is  turned  to  swing  them 
outward.  The  construction  of  the  main  cell  in  this  machine  does 
not  exhibit  any  departures  from  the  regulation  Farman  form,  but 
in  the  machine  with  the  set-in  ailerons,  which  also  made  its  debut 
at  the  Paris  Salon  at  the  end  of  1911,  the  planes  are  "staggered," 
i.  e.,  the  lower  plane  is  very  much  shorter  than  the  upper,  and  they 
are  connected  by  diagonal  steel  struts,  thus  doing  away  with  the 
maze  of  wire  braces.  A  single  surface  tail  is  employed  in  connection 
with  front  and  rear  elevators  and  twin  vertical  rudders. 


TYPES   OF   AEROPLANES  35 

The  Maurice  Farman  biplane  differs  somewhat  from  the 
machines  just  described  (Henri  Farman),  the  two  brothers  having 
at  first  operated  independently.  It  is  noteworthy  for  its  remarkable 
duration  performances.  It  was  in  one  of  the  Maurice  Farman 
biplanes  that  Tabuteau  broke  the  1909  world's  duration  record  of 
244  miles  in  5  hours  3  minutes  5  seconds,  by  traveling  290  miles  in 
6:8: 12  (October  28,  1910),  which  he  increased  on  December  30, 1910, 
to  365  miles  in  7:48:31,  thereby  winning  the  Michelin  cup.  The 
same  machine  also  won  the  $20,000  prize  for  the  flight  from  Paris 
with  a  passenger  to  the  Puy  de  Dome,  a  mountain  4,800  feet  high 
and  235  miles  distant.  Numerous  attempts  had  been  made  to  win 
this  during  three  successive  years.  The  Farman  biplane  covered  the 
distance  in  5:10:46,  including  a  stop  of  14  minutes,  the  time  limit 
in  which  the  prize  could  be  won  being  six  hours,  which  included 
circling  the  Arc  de  Triomphe  in  Paris  and  the  steeples  of  the  cathe- 
dral at  Clermont-Ferrand  near  the  finish  as  part  of  the  conditions. 
The  machine  has  a  supporting  surface  of  635  square  feet  and  an 
aspect  ratio  of  8  to  1.  Its  weight  is  1,210  pounds  and  with  a  60- 
horse-power  Renault,  eight-cylinder,  air-cooled  motor  its  speed  is  48 
miles  per  hour.  The  propeller  is  driven  from  the  cam  shaft  instead 
of  the  crank  shaft,  so  that  at  a  motor  speed  of  1,800  r.  p.  m.,  it 
makes  900  r.  p.  m.  Maurice  Farman  was  the  first  to  employ  a 
covered  body  enclosing  the  seats  and  the  engine,  this  construction 
now  being  considered  essential  for  the  comfort  of  the  pilot  and 
passenger  on  all  Continental  aeroplanes,  though  up  to  the  beginning 
of  1912,  it  had  not  been  made  a  feature  of  any  of  the  American 
machines.  The  Farman  control  is  very  simple  and  effective.  It 
consists  of  a  hand  wheel  on  a  sliding  shaft  and  a  pair  of  pedals. 
Forward  and  backward  motion  of  the  wheel  controls  the  angle  of 
the  elevator,  while  rotation  of  the  wheel  operates  the  rudders,  the 
pedals  actuating  the  ailerons.  The  wheel  is  vertical,  its  shaft  passing 
horizontally  through  an  automobile  type  of  dash  on  which  are 
mounted  a  clock,  a  gradient  indicator,  an  aneroid  barometer,  and  a 
recording  barograph. 

Sommer.  In  June,  1909,  Roger  Sommer  purchased  a  biplane 
constructed  by  Henri  Farman  (the  machine  of  Maurice  Farman 
differs  in  design)  and  on  July  3  he  made  his  first  flight.  Scarcely  a 
month  later  he  held  what  was  then  the  world's  record  for  duration 


231 


fffOMT  £L£VAT/ON 

Fig.  23.     Details  of  Sommer  Biplane 


232 


TYPES   OF  AEROPLANES  37 

of  flight,  having  flown  continuously  for  two  and  one  half  hours.  His 
sudden  jump  into  the  ranks  of  the  great  aviators  was  remarkable 
and  showed  that,  after  all,  it  is  not  so  hard  to  learn  to  fly  well.  He 
won  many  prizes  at  Rheims  and  Doncaster  in  1909,  but  shortly 
afterward  gave  up  flying  on  the  Farman  biplane  and  proceeded  to 
design  and  build  one  of  his  own,  Fig.  23.  This  was  first  tried  out 
in  January,  1910,  and  after  a  few  days  of  experimenting  he  succeeded 
in  making  a  long  cross-country  flight.  The  Sommer  biplane  is  also 
operated  by  other  prominent  French  aviators. 

Frame.  The  construction  of  the  frame  is  chiefly  of  hickory  and 
ash  with  steel  joints  and  steel  tubing,  its  general  character  and 
appearance  being  similar  to  that  of  the  Farman. 

Supporting  Planes.  Two  identical  and  directly-superposed  rigid 
planes  carry  the  machine,  the  surfaces  being  made  of  rubber  cloth 
covering  wood  ribs.  The  sectional  curvature  of  the  surfaces  is  not 
so  highly  arched  as  in  most  other  types,  being  more  nearly,  as  in 
the  Wright  machine,  a  very  even  and  gently  sloping  curve.  The 
spread  of  the  planes  is  33  feet,  their  depth  5.2  feet,  and  their  area 
326  square  feet. 

Elevation  Rudder.  At  a  distance  of  8.25  feet  in  front  of  the 
main  cell,  and  supported  on  framing  carried  down  to  the  skids,  is 
placed  the  single-surface  elevating  rudder.  This  is  governed  by  a 
large  lever  held  in  the  aviator's  left  hand,  which,  when  pushed  out, 
turns  down  the  rudder  and,  when  pulled  in,  turns  it  up;  thus, 
respectively,  causing  (the  aeroplane  to  mount  or  descend. 

Direction  Rudder.  The  direction  rudder  consists  of  a  single 
surface  of  but  10  square  feet  in  area,  placed  at  the  rear.  It  is 
operated  by  a  pivoted  foot  lever  similar  to  that  of  the  Farman. 

Transverse  Control.  Lateral  equilibrium  is  secured  by  two  wing 
tips,  one  placed  at  either  end  of  the  rear  of  the  upper  plane,  as  shown 
clearly  in  Fig.  24,  there  being  no  ailerons  on  the  lower  main  plane 
as  in  the  Farman.  These  are  controlled  by  cables  leading  to  a 
brace  attached  to  the  aviator's  body.  By  leaning  to  the  right,  the 
wing  tip  on  the  left  is  pulled  down,  at  the  same  time  pulling  up  that 
on  the  right,  causing  the  left  end  of  the  machine  to  rise  and  the  right 
end  to  descend.  Though  not  interconnected,  the  direction  rudder 
and  the  transverse  control  are  operated  simultaneously  by  the  oper- 
ator, thus  giving  the  same  effect  as  is  obtained  in  the  Wright  and 


233 


38  TYPES   OF   AEROPLANES 

Farman  machines  by  controlling  these  two  elements  from  the  same 
lever. 

Keels.  A  single  horizontal  plane  of  55  square  feet  area  and  of 
very  light  construction  is  placed  at  the  rear  and  steadies  the  machine 
longitudinally.  This  plane  is  movable  though  it  does  not  act  as  a 
rudder.  A  lever  at  the  right  hand  of  the  operator,  which  auto- 
matically locks  in  place,  enables  the  angle  of  incidence  of  this  sur- 
face to  be  varied  at  will,  thus  increasing  the  attainable  stability. 

Power  Plant.  The  power  plant  consists  of  the  same  type  of 
rotary,  air-cooled,  seven-cylinder  Gnome  motor  as  employed  on  the 
Farman.  It  is  placed  at  the  rear  of  the  main  cell  and  is  attached 


Fig.  24.     Sommer  Biplane  Equipped  with  Gnome  Seven-Cylinder  Motor 

to  a  two-bladed  wood  propeller  of  7.2  diameter  by  a  5.2-foot  pitch, 
which  it  revolves  at  1,200  r.  p.  m. 

General.  Two  large  wheels  are  attached  forward  and  two  small 
wheels  at  the  rear  of  the  chassis,  the  front  wheels  being  held  by 
rubber  springs  to  two  skids,  built  under  the  frame.  The  skids  them- 
selves are  attached  to  the  main  frame  by  uprights,  the  joints  being 
made  of  a  springy  sheet  of  metal  bolted  to  the  framing.  This  adds 
still  further  to  the  resilient  character  of  the  mounting.  The  seat  for 
the  aviator  is  placed  on  the  front  of  the  lower  main  plane  at  the  center 
and  is  fitted  more  comfortably  than  on  most  other  biplanes  which 
had  been  built  up  to  that  time. 

In  more  recent  machines  for  racing  purposes  the  two  end  panels 


234 


TYPES   OF  AEROPLANES  39 

of  the  lower  surface  of  the  Sommer  have  been  eliminated,  reducing 
the  spread  and  cutting  the  area  down  to  256  square  feet.  The  loading 
is  3.25  pounds  per  square  foot. 

Cody.  Colonel  Cody,  an  American,  for  a  long  time  resident  in 
England,  is  doubtless  best  known  in  this  field  through  his  connection 
with  the  successful  operation  of  man-carrying  kites  several  years  ago. 
His  work  in  this  line  for  military  scouting  attracted  considerable 
attention  in  England.  In  1907,  he  commenced  work  on  an  aeroplane 


Fig.  25.     Cody  Biplane  Ready  for  Flight 

of  huge  dimensions,  Fig.  25.  At  first,  the  tests  of  this  machine  were 
very  disappointing,  but  by  his  remarkable  perseverance  Colonel  Cody 
turned  failures  into  successes  and  finally,  in  the  late  summer  of  1909, 
accomplished  a  superb  flight  of  over  an  hour,  establishing  what  was 
then  the  world's  record  for  cross-country  flight.  The  machine  has 
been  altered  a  number  of  times,  and  in  its  form  as  settled  upon  in 
the  spring  of  1910,  Fig.  26,  was  the  largest  successful  aeroplane 
in  use. 

Frame.  Bamboo  is  employed  extensively  throughout  the  frame 
but  all  joints  are  wound  with  steel  wire.  In  addition,  there  are  a 
number  of  upright  members  of  ash.  At  the  center  several  members 


235 


SIDE  EL  EVA 


Fig.  26.     Details  of  Cody  Biplane 


236 


TYPES   OF  AEROPLANES  41 

meet  in  the  supporting  chassis  which  is  very  heavily  built.    Steel  wire 
is  used  for  bracing. 

Supporting  Planes.  The  main  planes  are  of  rectangular  form 
with  rounded  rear  edges.  They  are  identical  and  directly  superposed, 
the  surfaces  being  made  of  canvas  tightly  stretched  over  wood  ribs./ 
At  the  center,  the  distance  between  them  is  9  feet,  but  they  converge 
slightly  toward  either  end  where  they  are  separated  by  only  8  feet. 
The  spread  is  52  feet,  the  depth  7.5  feet,  and  the  area  780  square  feet. 

Elevation  Rudder.  At  the  front  of  the  machine,  supported  by 
large  bamboo  outriggers  from  the  central  cell,  are  two  equal  surfaces 
placed  on  either  side  of  the  center.  They  are  jointly  movable  and 
serve  to  control  the  elevation  of  the  machine.  They  are  governed  by 
the  forward  or  backward  movement  of  the  stanchion  to  which  the 
steering  wheel  is  attached,  in  the  same  manner  as  on  the  Curtiss.  If 
the  aviator  wishes  to  rise,  he  pulls  the  wheel  toward  him.  This  motion, 
by  means  of  a  lever  system,  causes  the  elevating  rudder  surfaces  to 
be  tilted  upward  to  the  line  of  flight  and  the  machine  ascends. 

Direction  Rudders.  Two  direction  rudders  are  employed,  a 
large  one  at  the  rear  and  a  small  one  in  front,  the  former  consti- 
tuting the  main  rudder.  These  rudders  are  moved  together  by  a 
steering  wheel  and  cables  as  in  a  motorboat.  Their  combined  area 
is  about  40  square  feet. 

Transverse  Control.  Two  balancing  planes  of  30  square  feet  area, 
one  placed  at  either  end  of  the  main  cell,  control  the  transverse 
inclination  of  the  machine.  They  are  moved  inversely  by  cables  lead- 
ing from  the  steering  gear  and  operate  in  the  same  manner  as  the 
ailerons  of  the  Curtiss  machine  and  the  wing  tips  of  the  Farman  and 
Sommer  biplanes,  one  balancing  plane  being  turned  up  while  the  other 
is  turned  down.  Lateral  stability  is  also  controlled  by  the  inverse 
movement  of  the  two  halves  of  the  elevation  rudder,  the  one  on  the 
depressed  side  being  elevated  while  the  other  is  turned  down.  There 
are  no  keels  on  the  Cody  biplane,  all  surfaces  serving  either  to  lift 
or  direct  the  machine. 

Power  Plant.  The  power  plant  is  an  eight-cylinder,  80-horse- 
power  E.  N.  V.  motor  placed  near  the  forward  edge  of  the  lower 
main  plane  and  directly  back  of  the  aviator.  It  drives  two  two-bladed 
wood  propellers  mounted  on  shafts  located  at  their  front  end  half  way 
between  the  main  planes.  These  are  driven  in  opposite  directions  by 


237 


42  TYPES   OF   AEROPLANES 

means  of  chains,  as  in  the  Wright  biplane.  These  propellers  have 
a  diameter  of  8.25  feet  and  a  pitch  of  6  feet;  and  are  revolved  at 
600  r.  p.  m. 

General.  The  mounting  consists  of  a  large  pair  of  wheels  which 
carry  most  of  the  weight,  a  small  wheel  in  front  and  a  skid  at  the 
rear.  Wheels  are  also  attached  to  the  outer  ends  of  the  lower  plane 
to  carry  the  machine  easily  over  the  ground  should  it  alight  on  end. 
The  total  weight  is  from  1,900  to  2,100  pounds;  speed  37  miles  per 
hour;  25  pounds  per  horse-power  are  lifted  and  2.57  pounds  per 
square  foot  of  supporting  surface.  The  aspect  ratio  is  high — 7  to  1. 
Seats  are  provided  for  the  aviator  and  for  one  passenger,  both  being 
placed  low  at  the  center  of  the  front  of  the  main  cell,  that  for  the 
passenger  being  higher  than  that  for  the  aviator,  as  it  is  designed 
for  the  use  of  an  observer  in  war  time. 

Since  the  machine  was  first  built,  the  E.  N.  V.  motor  has  been 
replaced  by  two  50-horse-power,  four-cylinder  Green  motors,  both 
driving  a  single  propeller  instead  of  the  twin  propellers  formerly 
used.  Either  motor  can  be  operated  independently,  the  advantage 
of  this  arrangement  being  that  if  one  motor  breaks  down  while  in 
flight  the  other  can  still  be  used  to  drive  the  machine. 

MONOPLANES 

Antoinette.  Up  to  the  time  of  the  present  writing,  the  Antoi- 
nette, Fig.  27,  is  the  largest  monoplane  in  use  and  its  construction 
is  distinguished  by  a  number  of  features  not  found  on  others.  Leva- 
vasseur,  designer  of  the  Antoinette  motor  and  motorboats,  is  cred- 
ited with  the  design  of  this  type.  After  building  some  experimental 
machines,  notably  the  Gastambide-Mengin  monoplane,  the  Antoi- 
nette IV  was  built  for  Hubert  Latham.  This  machine  was  at  first 
controlled  transversely  by  means  of  wing  tips,  but  the  warpable 
surface,  or  Wright  control,  has  since  been  adopted.  The  Antoinette 
is  remarkably  well  built  from  an  engineering  standpoint  and  has 
been  successfully  operated  by  M.  Latham  in  high  winds,  though  not 
as  strong  as  the  gale  in  which  the  two  Wright  biplanes  were  blown 
backward  30  and  40  miles  from  Belmont  Park  at  the  International 
Meet,  despite  all  they  could  do.  The  Antoinette  is  also  flown  by 
other  prominent  French  aviators  and  several  of  the  machines  have 
been  purchased  by  the  French  War  Department. 


238 


TYPES   OF  AEROPLANES 


43 


Frame.  The  frame  is  of  long,  narrow,  girder-like  construction, 
Fig.  28,  of  cedar,  ash,  and  aluminum,  carrying  at  its  forward  part 
the  main  plane,  the  "nacelle"  or  car  for  the  aviator,  and  at  its  extreme 
front  end  the  propeller,  while  at  the  opposite  end  are  placed  the 
rudders,  the  longitudinal  dimensions  of  the  machine  being  in  excess 
of  36  feet,  or  almost  three  fourths  as  much  as  its  spread.  The  arrange- 
ment of  the  planes  and  rudder,  as  well  as  the  location  of  the  motor, 
is  similar  to  that  in  all  the  monoplanes  described  here  with  the  excep- 
tion of  the  Pfitzner. 

Supporting  Plane.  The  supporting  plane  consists  of  a  single 
surface  divided  in  half,  the  two  sections  being  of  trapezoidal  shape, 
placed  at  a  slight  dihedral  angle  to  each  other.  They  are  constructed 


Fig.  27.     Two  Antoinette  Monoplanes  Competing  at  Belmont  Park,  1910 

of  rigid  trussing,  nearly  a  foot  thick  at  the  center  and  covered  over 
and  under  with  a  smooth,  finely-pumiced  silk.  The  plane  is  also 
braced  from  a  central  mast.  The  spread  is  46  feet,  the  average 
depth  8.2  feet,  and  the  surface  area  370  square  feet. 

Direction  Rudder.  The  direction  rudder  consists  of  two  ver- 
tical triangular  surfaces  at  the  rear  and  measures  10  square  feet  in 
area.  These  surfaces  are  moved  jointly  by  means  of  wiring  cables 
worked  by  a  lever  operated  by  the  aviator's  feet.  When  this  lever, 
which  moves  in  a  horizontal  plane,  is  turned  to  the  left,  the  machine 
will  change  its  course  in  the  same  direction. 


239 


Fig.  28.     Details  of  Antoinette  Monoplane 


240 


TYPES   OF  AEROPLANES  45 

Elevation  Rudder.  The  elevation  rudder  has  an  area  of  20 
square  feet  and  is  also  triangular.  It  is  placed  at  the  extreme  rear 
in  order  to  provide  the  maximum  leverage,  and  is  controlled  by 
cables  leading  round  a  drum  attached  to  a  wheel  at  the  aviator's 
right  hand.  To  ascend,  the  wheel  is  turned  up.  This  causes  the 
inclination  of  the  elevating  rudder  with  regard  to  the  line  of  flight 
to  decrease,  and  the  machine,  therefore,  rises. 

Transverse  Control.  Lateral  stability  is  maintained  by  warp- 
ing the  outer  ends  of  the  main  plane  in  much  the  same  manner  as 
in  the  Wright  machine,  except  that  the  front  ends  of  the  plane  are 
movable  and  the  rear  ends  are  rigid  throughout  in  the  Antoinette, 
the  reverse  being  the  case  in  the  Wright.  Through  cables  and  a 
sprocket  placed  at  the  lower  end  of  the  central  mast,  the  warping 
is  controlled  by  a  wheel  at  the  aviator's  left  hand.  To  correct  a 
downward  inclination  at  the  right,  the  right  end  of  the  wing  is  turned 
up  and  at  the  same  time  the  left  end  is  turned  down,  restoring  the 
balance. 

Keels.  At  the  rear,  leading  up  to  the  rudders,  are  tapered 
keels,  both  horizontal  and  vertical,  that  add  greatly  to  the  bird- 
like  appearance  of  the  Antoinette  in  flight. 

Power  Plant.  The  power  plant  is  an  eight-cylinder,  V-type;. 
four-cycle,  water-cooled  Antoinette  motor  of  50  horse-power,  the 
radiator  taking  the  form  of  two  banks  of  tubes  placed  along  either 
side  of  the  car.  The  motor  carries  on  the  forward  end  of  its  crank 
shaft  a  two-bladed,  Wetal  propeller,  7.25  feet  in  diameter  by  4.3 
feet  pitch,  which  it  drives  at  1,100  r.  p.  m. 

General.  The  chassis  is  mounted  on  a  pair  of  pneumatic-tired 
wheels  attached  to  the  central  mast  by  a  pneumatic  spring.  In  addi- 
tion, a  single  skid  is  placed  forward  to  protect  the  propeller  in  land- 
ing, and  another  at  the  rear.  The  seat  for  the  aviator  is  placed  in 
the  frame  back  of  the  main  plane  and  about  8  feet  directly  behind 
the  motor,  a  seat  for  a-  passenger  being  provided  in  front  of  and 
slightly  lower  than  that  for  the  aviator.  The  sides  of  the  space  are 
walled  with  canvas,  affording  the  aviator  and  passenger  more  pro- 
tection than  is  usually  provided.  The  total  weight  is  1,040  to 
1,120  pounds,  the  speed  43  miles  per  hour.  Thirty  pounds  are  lifted 
per  horse-power  and  3.96  pounds  per  square  foot  of  supporting  sur- 
face. The  aspect  ratio  is  6  to  1. 


241 


46  TYPES   OF  AEROPLANES 

In  a  later  machine,  the  spread  is  49.3  feet,  the  area  405  square 
feet,  and  the  -total  weight  1,200  to  1,350  pounds,  27  pounds  being 
lifted  per  horse-power,  and  3.33  pounds  per  square  foot  of  surface. 
The  aspect  ratio  is  6  to  1.  A  new  100-horse-power  type  is  also 
employed  for  racing,  this  machine  being  fitted  with  the  Antoinette 
sixteen-cylinder,  V-type  motor.  The  newer  models  of  the  Antoinette 
differ  so  radically  that  they  have  been  described  in  the  article 
devoted  to  special  types. 

Santos=Dumont.  The  first  sustained  flight  of  a  motor-driven 
aeroplane  in  Europe  was  made  by  M.  Santos-Dumont  on  November 


Fig.  29.     Santos-Dumont's  Earliest  Aeroplane  with  Which  He  Made  the 
First  Power  Flight  in  Europe 

12,  1906,  in  a  biplane  of  his  own  design,  Fig.  29.  In  1907  he  began 
work  on  a  monoplane  and  after  a  great  deal  of  experimenting  suc- 
ceeded in  evolving  the  Demoiselle,  Fig.  30,  so-called  owing  to  its 
diminutive  size,  as  it  is  the  smallest  aeroplane  in  use  up  to  the  pres- 
ent writing.  It  is  extremely  simple  and  compact  and  many  of  them 
are  flown  abroad.  Some  of  Santos-Dumont's  earlier  attempts  were 
based  on  principles  attractive  in  theory,  but  which  experience  has 


242 


TYPES   OF   AEROPLANES  47 

shown  to  be  erroneous.  Chief  among  these  are  the  use  of  a  sharp 
dihedral  angle  for  the  supporting  surfaces  and  a  very  low  center  of 
gravity  to  simulate  a  pendulum.  As  shown  by  the  Wright  Brothers' 
experiments,  while  a  pendulum  may  give  a  certain  stability  in  a 
state  of  perfect  rest  or  when  flying  straightaway  in  a  dead  calm,  it 
exaggerates  oscillation,  once  the  latter  is  set  up,  and  is  entirely 
destructive  of  stability.  Planes  set  at  a  dihedral  angle  give  neither 
the  same  lifting  power  nor  an  amount  of  stability  equal  to  a  surface 
of  the  same  dimensions  that  is  made  perfectly  flat  laterally.  This 
is  the  case  in  all  the  biplanes  described  here  and  some  of  the  mono- 
planes, the  supporting  surfaces  of  the  Bleriot  and  Antoinette  being 
set  at  a  slight  dihedral  angle,  however.  This  characteristic  is  still 


Fig.  30.     Santos-Dumont  Demoiselle,  the  Smallest  Man-Carrying  Aeroplane 

strongly  marked  in  the  Santos-Dumont  monoplane,  but  the  motor 
has  been  placed  on  a  level  with  the  supporting  surfaces.  The  lack 
of  stability  of  this  machine  was  very  marked  as  compared  with  both 
the  biplanes  and  monoplanes  taking  part  in  the  International  Meet 
near  Xew  York,  both  its  pitching  and  rocking  reaching  extreme 
angles  and  continuing  throughout  the  flight.  When  compared  with 
the  larger  machines  in  the  air,  it  appeared  almost  like  a  sparrow 
among  eagles,  and  the  difference  in  the  character  of  their  action  in 
flight  was  also  similar.  At  no  time  did  Audemars  or  Garros  leave  the 
ground  more  than  30  or  40  feet  below,  when  flying  the  Demoiselle 
monoplanes  on  the  occasion  in  question. 


243 


F&OJVT  ELEVATIOM 


Fig.  31.     Details  of  Santos-Dumont  Demoiselle 


244 


TYPES   OF   AEROPLANES  49 

Frame.  The  frame  is  triangular  in  form,  Fig.  31,  with  its  apex 
at  the  rear  and  is  composed  of  bamboo  with  steel  joints  and  several 
members  of  steel  tubing. 

Supporting  Planes.  Owing  to  the  curvature  of  the  supporting 
surfaces  closely  approximating  the  arc  of  a  circle,  there  are  really 
two  planes  joined  at  their  inner  ends.  They  consist  of  a  double  layer 
of  silk  tightly  stretched  over  bamboo  ribs,  the  whole  being  braced  by 
steel  wires  led  to  the  central  frame.  The  spread  is  18  feet,  the  depth 
6.56  feet,  and  the  area  113  square  feet. 

Direction  and  Elevation  Rudders.  The  direction  and  elevation 
rudders  are  combined  at  the  rear  in  the  form  of  two  fan-shaped 
surfaces,  one  vertical  and  the  other  horizontal,  swung  on  a  universal 
joint  at  the  point  of  the  triangular  frame.  The  elevating  rudder  has 
an  area  of  21  square  feet,  while  the  direction  rudder  is  somewhat 
smaller.  A  lever  at  the  aviator's  right  hand  controls  the  elevating 
rudder,  while  a  wheel  at  the  left  operates  the  direction  rudder.  To 
ascend,  the  tail  is  moved  up  and  to  the  right,  to  alter  the  line  of  travel 
in  that  direction.  There  are  no  keels. 

Transverse  Control.  Transverse  control  is  accomplished  by 
warping  the  main  planes,  their  operation  being  governed  by  a  lever 
at  the  back  of  the  aviator  which  fits  into  a  pocket  sewed  into  his 
coat.  If  the  machine  should  suddenly  tip  up  on  the  left,  the  aviator, 
by  moving  quickly  in  that  direction,  could  pull  down  the  plane  on 
the  right  and  increase  the  angle  of  incidence  on  that  side.  It  will  be 
seen  from  the  foregoing  that  in  flight  he  is  kept  pretty  busy.  The 
flexibility  of  the  ribs  of  the  planes  permits  them  to  warp  without  any 
special  constructional  details  for  that  purpose. 

Power  Plant.  A  30-horse-power,  two-cylinder,  horizontal-opposed 
water-cooled  Darracq  motor  drives  a  two-bladed  Chauviere  wood  pro- 
peller 6.9  feet  in  diameter  by  6-foot  pitch  at  1,400  r.  p.  m.,  although 
Clement-Bayard  and  Panhard  motors  are  also  used  on  this  machine. 

General.  The  machine  is  mounted  on  two  rigidly  attached 
pneumatic-tired  wheels  at  the  front  and  a  single  small  skid  at  the 
rear,  the  aviator's  seat  consisting  of  a  strip  of  canvas  placed  across 
the  frame  and  located  directly  beneath  the  motor.  The  propeller, 
instead  of  extending  forward  beyond  the  main  planes,  revolves  in  a 
rectangular  opening  cut  in  the  latter.  The  total  weight  is  from  330 
to  370  pounds,  speed  52  miles  per  hour.  Twelve  pounds  are  lifted 


245 


FROHT    ELEVAT/ON 

Fig.  32.     Details  of  Bleriot  XI  Monoplai 


246 


TYPES   OF   AEROPLANES  51 

per  horse-power  and  3.1  pounds  per  square  foot  of  surface.  The 
aspect  ratio  is  2.7  to  1. 

Bleriot  XI.  In  1906,  M.  Louis  Bleriot  constructed  and  flew  the 
first  successful  monoplane  built.  The  two  years  following  were 
devoted  to  experimental  work,  during  which  period  a  number  of 
various  modifications  of  the  original  were  built  until,  in  1908,  Bleriot 
succeeded  in  making  a  number  of  extended  flights  in  his  large  mono- 
plane, No.  8  Bis.  In  July,  1910,  he  made  his  sensational  cross- 
channel  trip,  starting  from  Calais  and  landing  near  Dover.  This 
flight  was  accomplished  in  the  No.  XI  type  machine,  Fig.  32,  a  small 
one-passenger  monoplane  which  is  very  simple  and  has  come  into 
widespread  use  abroad.  Delagrange,  Le  Blanc,  De  Lesseps,  Le  Blon, 
Balsan,  and  Guyot  are  among  some  of  the  noted  French  aviators 
who  have  flown  Bleriot  monoplanes,  two  of  whom  have  been  killed 
in  their  operation.  More  than  one  hundred  and  forty  of  these  machines 
were  manufactured  and  sold  during  the  year  ending  with  August,  1910. 

Frame.  The  frame  consists  essentially  of  a  long  central  body 
of  tapering  construction  to  which  the  planes  and  rudder  are  attached. 
The  framework  is  very  lightly  but  strongly  built  of  wood  and  is 
cross  braced  with  steel  wires  throughout. 

Supporting  Plane.  The  main  plane  is  placed  at  the  forward  part 
of  the  central  frame  and  is  divided  in  half,  each  section  being  mounted 
on  either  side  of  the  central  frame  by  socket  joints.  The  halves  are 
thus  readily  detachable  at  that  point  and  when  not  in  use  are  dis- 
mounted and  placed  in  a  vertical  position  along  the  frame  so  as  to 
make  the  machine  as  a  whole  occupy  very  little  room.  The  surfaces 
consist  of  wood  ribs  covered  both  above  and  below  by  Continental 
rubber  fabric.  The  curvature  is  more  pronounced  than  in  most  other 
types,  with  the  exception  of  the  Demoiselle,  and  a  sharp  front  edge 
is  obtained  by  the  use  of  aluminum  sheathing  at  that  point.  The 
two  halves  of  the  main  plane  are  set  at  a  slight  dihedral  angle.  Their 
spread  is  28.2  feet,  depth  6.5  feet,  and  surface  area  151  square  feet. 
They  are  braced  both  above  and  below  by  steel  wires  led  to  the 
central  frame. 

Direction  Rudder.  The  direction  rudder  consists  of  a  very  small 
plane  having  only  4.5  square  feet  of  area  and  is  placed  at  the  extreme 
rear.  It  is  controlled  by  a  foot  in  the  manner  already  described  in 
some  of  the  foregoing  machines. 


247 


52  TYPES   OF   AEROPLANES 

Elevation  Rudder.  The  elevation  rudder  is  divided  into  two 
parts,  one  half  being  mounted  at  each  extremity  of  a  fixed  horizontal 
keel.  It  has  16  square  feet  of  surface  and  is  operated  by  the  longi- 
tudinal movement  of  a  bell  crank  device.  This  takes  the  form  of  a 
universally-pivoted  lever  placed  in  front  of  the  operator,  and  is 
normally  vertical.  At  the  lower  extremity  of  the  lever  is  fixed  a 
dome  or  hood-shaped  piece  of  metal  to  which  the  wires  are  attached, 
at  the  same  time  protecting  them  from  entanglement  in  the  aviator's 
feet.  To  ascend  the  aviator  pulls  the  lever  toward  him,  and  to  descend 
pushes  it  from  him. 

Transverse  Control.  Lateral  equilibrium  is  maintained  by  warp- 
ing the  main  planes,  the  structure  of  the  latter  enabling  them  to  be 
twisted  as  in  the  Wright  machine,  though  in  this  case  they  warp 
about  the  bases  which  are  rigidly  attached  to  the  main  frame  by  the 
socket  joints  mentioned.  The  two  halves  are  warped  inversely  by 
the  side  to  side  motion  of  the  bell  crank,  i.  e.,  if  the  machine  should 
tip  up  on  the  right,  then  the  bell  crank  would  be  moved  to  the  right. 
This  would  increase  the  incidence  of  the  lowered  side  and  at  the 
same  time  decrease  that  of  the  raised  side,  thus  righting  the  machine. 
The  combination  of  this  side  to  side  movement  of  the  bell  crank 
with  the  movement  of  the  foot  lever  controlling  the  direction  rudder 
is  used  in  turning. 

Keels.  To  preserve  the  longitudinal  stability,  a  single,  fixed, 
horizontal  keel  is  placed  at  the  rear.  Its  area  is  17  square  feet. 

Power  Plant.  The  power  plant  is  a  three-cylinder,  fan-shaped 
Anzani  motor,  developing  23  horse-power.  It  is  of  the  air-cooled 
type  and  is  placed  at  the  forward  end  of  the  central  frame.  It  drives 
a  two-bladed  wood  propeller  of  6.87  feet  in  diameter  by  2.7-foot 
pitch  direct  at  1,350  r.  p.  m.  Most  of  the  more  recent  Bleriot 
monoplanes  have  been  fitted  with  50-horse-power  Gnome,  seven- 
cylinder,  rotary,  air-cooled  motor. 

General.  The  machine  is  mounted  on  an  elastic  chassis  with 
two  large  rubber-tired  wheels  forward  and  a  small  wheel  rear.  The 
springs  are  made  of  thick  rubber  rope,  affording  great  elasticity  and 
strength  with  small  weight.  The  aviator's  seat  is  back  of  the  main 
plane. 

The  total  weight  is  from  650  to  720  pounds  and  the  speed  is  36 
miles  per  hour  with  the  Anzani  motor  and  48  miles  per  hour  with  the 


248 


TYPES   OF   AEROPLANES 


53 


Gnome  motor;  29  pounds  are  lifted  per  horse-power  and  4.5  pounds 
per  square  foot  of  surface,  this  ratio  being  unusually  high.  The 
aspect  ratio  is  4.35  to  1. 

Later  Types.  In  the  later  Bleriot  machines,  the  elevating  rudder 
is  of  different  form,  being  attached  at  the  rear  edge  of  a  tapering 
keel  much  larger  than  that  formerly  used.  The  small  wheel  at  the 
rear  has  been  replaced  by  a  skid  and  the  overall  length  of  the  central 
frame  has  been  shortened  considerabty.  The  regular  one-passenger 
type  of  this  monoplane  has  further  been  altered  to  the  new  No.  XI 
Bis,  in  which  the  sectional  curvature  of  the  planes  has  been  made 
very  nearly  flat  on  the  under  side.  This  change  has  been  found  to 


Fig.  33.     Bleriot  Two-Passenger  Monoplane 

greatly  decrease  the  dynamic  resistance  of  the  machine  without 
seriously  impairing  its  lift.  There  are  two  new  models  of  this  machine 
which  have  been  very  successful.  They  are  the  No.  XI  2  Bis,  a  two- 
or  three-passenger  machine,  Fig.  33,  and  the  No.  XI  racing  model, 
Figs.  34  and  35.  The  former  has  a  spread  of  36  feet,  a  depth  of  7.6 
feet,  a  surface  of  270  square  feet,  and  a  weight  in  flight  of  about  990 
pounds.  In  other  respects  it  resembles  the  No.  XI  Bis.  19.8  pounds 
are  carried  per  horse-power  and  3.68  pounds  per  square  foot  of  sur- 
face. The  aspect  ratio  is  4.75  to  1.  The  type  de  course,  or  No. 
XI  racing  model,  is  the  machine  on  which  Morane  established  the 
record  of  almost  69  miles  per  hour.  It  has  a  very  short  body,  flat 


249 


54  TYPES   OF   AEROPLANES 

planes,  and  a  reinforced  frame.     The  surface  has  been  reduced  to 
129  square  feet  and  it  is  equipped  with  one  of  the  new  100-horse-power, 


Fig.  34.     Bleriot  Racing  Model  in  Fl'ght 

fourteen-cylinder  Gnome,  rotary,  air-cooled  motors.  The  total 
weight  is  about  750  pounds;  only  7.5  pounds  are  carried  per  horse- 
power and  as  much  as  5.76  pounds  are  lifted  per  square  foot  of  surface. 


Fig.  35.     Bleriot  Rounding  a  Pylon  in  International  Race  for  Gordon-Bennett  Cup 

Bleriot  XII.    The  Bleriot  XII  is  a  passenger-carrying  type  which 
differs  in  construction  from  those  just  described.     With  one  of  these. 


250 


TYPES   OF   AEROPLANES  55 

large  machines,  M.  Bleriot  made  the  first  flight  in  an  aeroplane  carry- 
ing three  passengers.  It  has  since  come  into  general  use,  more  than 
thirty  of  them  having  been  built. 

Frame.  The  long  central  frame  of  wood,  Fig.  36,  braced  in 
every  panel  by  steel  cross  wires,  is  very  deep  forward  and  tapers 
gracefully  to  a  point  at  the  rear. 

Supporting  Plane.  On  the  upper  deck  of  the  central  frame  at 
the  front  is  placed  the  main  plane  which  is  continuous  and  per- 
fectly horizontal.  Its  structure  is  similar  to  that  of  the  No.  XI  and 
it  is  braced  by  a  number  of  wires  from  the  frame.  The  spread  is 
30.2  feet,  the  depth  7.6  feet,  and  the  total  area  228  square  feet. 

Direction  Rudder.  A  single  surface  placed  at  the  rear  extrem- 
ity of  the  vertical  keel  is  used  for  this  purpose.  Its  area  is  only  9 
square  feet  and  it  is  operated  in  the  same  manner  as  on  the  No.  XL 

Elevation  Rudder.  The  elevation  rudder  also  consists  of  a 
single  surface  of  20  square  feet  area  and  placed  at  the  extreme  rear. 
It  is  operated  by  the  movement  of  a  bell  crank,  as  already  described. 

Transverse  Control.  The  main  surfaces  are  warped  inversely, 
exactly  as  in  the  No.  XI,  a  small  surface  under  the  aviator's  seat 
also  assisting  in  the  lateral  balancing.  A  horizontal  keel  of  21 
square  feet  area  is  placed  on  the  framework  at  the  rear,  but  some- 
what forward  of  the  elevating  rudder. 

Power  Plant.  The  power  plant  consists  of  a  60-horse-power, 
eight-cylinder  E.  N.  V.,  air-cooled  motor,  placed  on  the  frame  under 
the  main  plane.  B^  means  of  a  chain  transmission  it  drives  an 
8.8-foot  propeller  mounted  on  a  shaft  at  the  edge  of  the  main  plane. 
The  propeller  has  an  unusually  long  pitch — 9  feet — and  turns  at 
only  600  r.  p.  m. 

General.  The  mounting  is  similar  to  that  of  No.  XI,  while 
the  seat  or  bench  for  three  persons  is  placed  under  the  main  plane 
and  back  of  the  motor.  The  total  weight  is  from  1,150  to  1,300 
pounds;  speed  48  miles  per  hour;  21  pounds  are  lifted  per  horse- 
power and  5.3  pounds  per  square  foot  of  surface.  The  aspect  ratio 
is  4  to  1 .  Bleriot  is  one  of  the  most  prolific  designers  of  monoplanes, 
and  it  would  require  a  volume  to  describe  them.  The  Bleriot  Lim- 
ousine or  "aerial  taxi"  is  described  under  special  types. 

Grade.  Herr  Grade  has  the  distinction  of  being  one  of  the  first 
German  aviators  to  design  and  build  an  aeroplane.  In  the  fall  of 


251 


56 


TYPES   OF   AEROPLANES 


PLAN 


\ 


. 


Fig.  36.     Details  of  Bleriot  XII  Monoplane 


252 


TYPES   OF   AEROPLANES 


57 


1909,  he  began  flights  on  his  interesting  monoplane,  Fig.  37,  and  on 
October  30,  1909,  won  the  Lanz  $10,000  prize  for  a  German-built 


ELEVAT/ON 

Fig.  37.     Grade  Monoplane,  One  of  the  Fe\y  German  Aeroplane  Designs 

machine.    The  machine  is  simple  and  flies  easily.     A  number   of 
them  have  already  been  built  and  sold  in  Germany. 


253 


58  TYPES   OF   AEROPLANES 

Frame.  The  frame  is  remarkable  for  the  simplicity  of  its  construc- 
tion, consisting  of  a  main  metal  tube  chassis  at  the  front  from  which 
a  long  thick  member  supporting  the  rudders  is  run  out  to  the  rear. 

Supporting  Plane.  The  main  surface  is  made  of  Metzler  rub- 
ber fabric  stretched  over  a  bamboo  frame.  The  surface  is  very 
flexible  and  the  two  ends  are  turned  up  slightly  from  the  center. 
The  curvature  is  almost  the  arc  of  a  circle  and  the  section  is  very 
thin.  The  spread  is  30  feet,  depth  7  feet,  and  area  208  square  feet. 

Direction  Rudder.  The  direction  rudder  consists  of  a  single, 
flexible  surface  of  16  square  feet  area,  carried  at  the  rear  and  con- 
trolled by  a  lever.  The  surface  itself  is  not  hinged, 'but  is  bent  in 
the  direction  desired  by  the  lever  and  wire  connections. 

Elevation  Rudder.  The  elevation  rudder  also  consists  of  a 
single  surface  placed  at  the  rear.  It  has  an  area  of  about  20  square 
feet  and  like  the  direction  rudder  its  operation  depends  upon  its 
flexibility.  It  is  controlled  by  a  large  lever  universally  pivoted  on 
the  frame  above  the  aviator.  To  rise,  this  lever  is  pulled  up,  and  to 
descend,  it  is  pushed  down,  thus  bending  up  or  down  the  rear  hori- 
zontal surface. 

Transverse  Control.  Warping  the  main  planes  is  resorted  to, 
the  operation  being  similar  to  the  Bleriot,  which,  in  turn,  is  pat- 
terned after  the  Wright. 

Keels.  The  tapering  ends  of  both  the  direction  and  elevating 
rudders  can  be  considered  as  keels,  an  additional  vertical  keel  being 
placed  forward,  both  above  and  below  the  main  plane. 

Power  Plant.  A  four-cylinder,  V-type,  air-cooled  motor  of  24 
horse-power  is  placed  at  the  front  edge  of  the  plane.  It  drives  direct 
at  1,000  r.  p.  m.  a  two-bladed  metal  propeller  6  feet  in  diameter  by 
a  4-foot  pitch. 

General.  Two  wheels  are  employed  forward  and  one  rear  for 
the  mounting,  no  springs  being  provided.  The  front  wheels  are 
provided  with  a  brake  to  bring  the  machine  to  a  quick  standstill  after 
alighting,  this  being  an  important  feature  where  the  space  is  limited. 
The  seat  is  placed  under  the  main  plane  and  consists  of  a  hammock- 
like  piece  of  cloth  which  is  >  very  light  and  very  comfortable.  The 
total  weight  is  from  350  to  450  pounds  and  the  speed  approximately 
44  miles  per  hour;  17  pounds  are  lifted  per  horse-power,  and  1.9 
pounds  per  square  foot  of  surface.  The  aspect  ratio  is  3.2  to  1. 


254 


TYPES   OF   AEROPLANES  59 

Pelterie.     By  many,  the  Pelterie  monoplane,  Fig.  38,  is  con- 
sidered to  be  one  of  the  most  perfect  types  of  aeroplane.     Great 


EJLEM4.TIOH 


F-ROFtT  ELEl#\TJON 

Fig.  38.     Pelterie  Monoplane 


care  is  shown  in  its  construction  and  finish,  but  owing  to  motor 
troubles,  it  has  never  flown  for  any  length  of  time.     Its  designer, 


255 


60  TYPES   OF   AEROPLANES 

Robert  Esnault  Pelterie,  is  one  of  the  foremost  French  aviation 
scientists,  and  previous  to  building  this  machine,  he  conducted 
a  lengthy  series  of  gliding  experiments  of  considerable  interest. 

Frame.  The  central  frame,  somewhat  similar  in  form  to  a 
bird's  body,  is  made  largely  of  steel  tubing  and  is  quite  short.  All 
exposed  parts  are  covered  with  Continental  cloth. 

Supporting  Plane.  The  main  supporting  surface  is  particularly 
strong  and  solid,  being  made  of  steel  tubing  carrying  wood  ribs 
covered  with  Continental  cloth.  The  curvature  is  very  similar  to 
that  of  a  bird's  wing,  and  transversely  the  surface  curves  downward, 
dihedrally  from  the  center.  Very  little  bracing  is  necessary.  The 
spread  is  35  feet,  depth  6.1  feet,  and  the  area  214  square  feet. 

Direction  Rudder.  The  direction  rudder  consists  of  a  vertical 
rectangular  surface  of  8  square  feet  area  placed  below  the  central 
frame  at  the  rear.  It  is  operated  by  a  lever  at  the  aviator's  right. 

Elevation  Control.  There  is  no  elevation  rudder  in  the  Pelterie 
monoplane,  the  elevation  of  the  machine  being  accomplished  by 
changing  the  angle  of  incidence  of  the  main  planes  themselves.  To 
ascend,  for  instance,  the  aviator  pulls  the  lever  in  his  left  hand 
toward  him.  This  increases  the  angle  of  incidence  of  the  plane 
and  accordingly  increases  the  lift,  causing  the  machine  to  rise. 

Transverse  Control.  Each  half  of  the  main  plane  is  warpable 
about  its  base,  transverse  equilibrium  being  maintained  by  the 
inverse  warping  of  the  planes  in  the  usual  manner.  In  turning, 
both  the  left-hand  lever  controlling  the  warping  planes  and  the 
right-hand  lever  controlling  the  direction  rudder  are  simultaneously 
moved  to  the  side  desired.  It  is  worthy  of  note  here,  that  of  all 
aeroplanes  employing  the  Wright  system  for  maintaining  lateral 
stability — and  there  are  very  few  that  do  not — none  of  them  com- 
bines the  control  in  one  lever  in  the  same  ingenious  manner  as  found 
in  the  Wright  machine. 

Keels.  Vertical  and  horizontal  keels  consisting  of  gradually 
tapering  surfaces  are  fixed  to  the  frame  and  aid  in  preserving  stability. 
The  rear  horizontal  keel,  shaped  like  a  bird's  tail,  has  an  area  of  20 
square  feet. 

Power  Plant.  The  power  plant  consists  of  a  seven-cylinder, 
fan-shaped,  air-cooled  R.  E.  P.  (Robert  Esnault  Pelterie)  motor  of 
very  ingenious  design.  It  is  placed  at  the  front  and  drives  direct  a 


256 


TYPES   OF   AEROPLANES  61 

four-bladed  aluminum  and  steel  propeller  at  900  r.  p.  m.  Its  diameter 
is  6.6  feet  and  its  pitch  5  feet. 

General.  The  mounting  consists  of  a  large  single  wheel  carried 
on  a  combined  hydraulic  and  pneumatic  spring  at  the  center  of  the 
front,  with  a  smaller  wheel  on  the  same  center  line  at  the  rear. 
Wheels  are  also  placed  at  the  outer  ends,  or  tips,  of  the  supporting 
planes,  so  that  when  first  starting  to  run  along  the  ground,  the 
machine  is  inclined.  The  seat  is  placed  in  the  frame,  and  protected 
on  all  sides,  the  aviator's  shoulders  coming  flush  with  the  supporting 
surfaces.  The  total  weight  is  from  900  to  970  pounds;  speed  39  miles 
per  hour;  27  pounds  are  lifted  per  horse-power  and  4.4  pounds  carried 
per  square  foot  of  surface.  The  aspect  ratio  is  5.75  to  1. 

In  a  later  model  of  the  R.  E.  P.  the  fuselage  is  entirely  of 
steel  tubing  connected  by  welded  joints  and  the  whole  strongly 
trussed.  Each  wing  is  composed  of  two  ash  spars  covered  by  red 
Continental  rubberized  fabric.  The  method  of  attaching  the  wings 
to  the  fuselage  is  a  distinctive  feature.  In  most  monoplanes  the  ends 
of  the  spars  are  let  into  the  fuselage,  but  in  this  case  they  are  attached 
to  the  body  by  means  of  joints.  This  prevents  the  portions  of  the 
wings  near  the  fuselage  from  having  to  endure  abnormal  stresses  due 
to  their  attachment  in  case  the  supporting  stays  should  become 
slack.  This  arrangement  also  permits  the  dihedral  angle  between 
the  wings  to  be  varied  slightly.  The  lower  stays  of  the  rear  spar  are 
attached  to  an  oscillating  lever  mounted  on  ball  bearings  and  con- 
trolled by  the  wing-Warping  lever,  while  the  lower  stays  attached  to 
the  front  spar  and  supporting  the  wings  in  flight  are  steel  cables 
covered  with  cloth.  The  tail  fins,  elevator,  and  rudder  are  demount- 
able, being  composed  simply  of  steel  tubing  covered  with  fabric. 
The  well-developed  horizontal  tail  fins,  being  distant  from  the  center 
of  gravity,  give  great  longitudinal  stability  to  the  machine.  The 
elevator,  which  forms  the  prolongation  of  the  horizontal  empennage 
or  tail,  is  divided  into  two  parts  by  the  rudder,  forward  of  which  is 
the  vertical  keel.  . 

Pfitzner.  The  Pfitzner  machine,  Fig.  39,  represents  a  radical 
departure  from  all  other  aeroplanes  in  some  of  its  features,  while  it 
differs  from  other  monoplanes  in  the  placing  of  the  aviator,  motor, 
and  rudders.  It  was  built  in  the  early  part  of  January,  1910,  by 
A.  L.  Pfitzner  at  the  Curtiss  factory  in  Hammondsport,  New  York. 


257 


62 


TYPES   OF   AEROPLANES 


It  was  the  first  to  employ  the  comparatively  simple  and  efficient 
method  of  transverse  control  by  means  of  sliding  surfaces,  and  while 


S/DE  ELEVAT/ON 


ELEVATION    U 

Fig.  39.     Details  of  Pfitzner  Monoplane 


the  first  flights  were  short,  largely  due  to  the  inexperience  of  the 
aviator,  it  is  considered  by^many  to  be  a  very  promising  type,  par- 


258 


TYPES   OF   AEROPLANES  63 

ticularly  as  it  does  not  conflict  with  the  Wright  system  in  any  way. 

Frame.  The  framework  is  largely  a  combination  of  numerous 
king-post  trusses  with  spruce  compression  members  and  wire  tension 
members.  The  framework  is  open  throughout,  enabling  quick 
inspection  and  easy  repairs.  At  the  center,  the  chassis  is  mainly 
composed  of  steel  tubing. 

Supporting  Plane.  The  main  supporting  plane,  a  5-degree 
dihedral  angle,  consists  of  two  main  beams,  across  which  are  placed 
spruce  ribs.  The  surface  is  made  of  Baldwin  vulcanized  silk  of  jet- 
black  color  tacked  to  the  top  of  the  ribs  and  laced  to  the  frame.  The 
curvature  of  the  surface  is  slight  and  is  designed  for  high  speed. 
The  spread  is  31  feet,  depth  6  feet,  and  surface  area  186  square  feet. 

Direction  Rudder.  The  direction  rudder  is  a  rectangular  surface 
of  but  6  square  feet  in  area  and  is  placed  at  the  front.  It  is  operated 
by  wires  leading  to  the  bracket  underneath  the  controlling  column. 
Turning  this  column  to  either  side  causes  the  machine  to  turn  to 
that  side. 

Elevation  Rudder.  The  elevation  rudder  is  likewise  placed  at 
the  front  and  is  also  a  single  surface  of  17  square  feet  in  area.  It  is 
operated  by  wires  leading  to  a  lever  at  the  side  of  the  controlling 
column.  Moving  the  column  forward  or  backward  causes  the  eleva- 
tion rudder  to  turn  down  or  up,  respectively. 

Transverse  Control.  The  framework  of  the  main  plane  is  carried 
out  30  inches  beyond  the  end  of  the  surface  on  either  side  and  affords 
a  place  for  a  rail  on  which  the  auxiliary  sliding  surfaces  move.  These 
sliding  surfaces,  or  equalizers,  are  each  12 J  square  feet  in  area  and 
when  "normal"  project  15  inches  beyond  the  end  of  the  fixed  surface 
on  either  side.  They  are  interconnected  by  wires,  and  a  long  cable 
running  to  each  end  through  a  pulley  connects  them  to  the  steering 
wheel.  The  control  is  as  follows:  If  the  right  end  of  the  aeroplane 
is  tipped  down,  the  wheel  supported  on  the  controlling  column 
is  turned  away  from  the  lowered  side.  This  causes  the  equalizer  on 
the  raised  end  to  be  pulled  in  under  the  main  surface,  or  "reefed," 
while  at  the  same  time  the  one  on  the  other  end  is  pulled  out.  This 
action  merely  decreases  the  surface  on  the  raised  end  and  increases 
it  on  the  lowered  end,  thus  righting  the  machine. 

Keels.  A  horizontal  surface  placed  at  the  rear  acts  as  a  longi- 
tudinal stabilizer.  It  is  10.5  square  feet  in  area  and  is  fixed  firmly 


359 


64  TYPES   OF   AEROPLANES 

to  the  supporting  framework,  10  feet  to  the  rear  of  the  main  surface. 

Power  Plant.  The  power  plant  consists  of  a  four-cylinder,  air- 
cooled,  25-horse-power  Curtiss  motor  placed  on  the  framework 
above  the  plane  and  to  the  rear  of  it.  The  motor  drives  direct  a 
two-bladed  wood  propeller  6  feet  in  diameter  by  4.5  feet  pitch  at 
1,200  r.  p.  m.  This  propeller  is  of  original  design  and  is  said  to  be 
very  efficient. 

General.  The  machine  is  mounted  on  four  small,  rubber-tired 
wheels  placed  at  the  lower  ends  of  the  four  main  vertical  posts  of 
the  chassis.  They  are  spaced  by  steel  tubing  and  are  fitted  with 
brakes,  but  have  no  springs.  The  seat  for  the  aviator  is  placed  out 
in  front  of  the  main  plane  and  directly  in  the  center  line.  The  total 
weight  in  flight  is  from  560  to  600  pounds,  while  the  speed  is  esti- 
mated at  42  miles  per  hour;  24  pounds  are  lifted  per  horse-power,  and 
3.2  pounds  carried  per  square  foot  of  surface.  The  aspect  ratio  is 
5.7  to  1. 

COMPARISON  OF  STANDARD  TYPES 

From  the  foregoing  description  of  what  has  been  termed  stand- 
ard types,  it  will  be  apparent  that,  while  all  have  many  features 
in  common,  no  two  are  exactly  alike  in  either  design,  constructional 
detail,  or  efficiency.  Some  that  are  less  desirable  from  certain  points 
of  view  than  other  types  belonging  to  the  same  class,  show  an  unus- 
ually high  degree  of  efficiency;  others  have  advantages  of  greater 
stability.  All,  however,  have  proved  successful  in  operation  and 
some  to  a  far  greater  degree  than  others.  It  will  accordingly  be 
both  interesting  and  profitable  to  note  the  contrasts  and  distinc- 
tions that  may  be  drawn.  From  these  it  will  be  possible  to  arrive 
at  conclusions  as  to  what  particular  features  are  most  desirable  at 
present,  as  well  as  to  note  what  the  trend  of  the  future  may  be.  For 
this  purpose  the  aeroplanes  already  described  are  compared  accord- 
ing to  the  following  essential  features,  which  are  given  as  nearly  as 
possible  in  the  order  of  their  importance,  where  their  influence  on 
the  result  aimed  at — flight — is  concerned:  (1)  transverse  control; 
(2)  aspect  ratio;  (3)  incident  angle;  (4)  propellers;  (5)  rudders;  (6) 
keels;  (7)  mounting;  (8)  speed;  (9)  flight;  (10)  efficiency. 

The  object  of  placing  the  factor  of  efficiency  last  in  order  of 
importance  is  not  to  indicate  that  as  its  actual  position  from  the 


260 


TYPES   OF   AEROPLANES  65 

practical  viewpoint,  as  this  is  the  one  thing  that  designers  are  now 
striving  hardest  to  attain,  but  more  because  it  represents  the  best 
opportunity  to  sum  up  generally  the  performances  of  the  different 
machines.  Motors  are  compared  at  the  conclusion  of  the  chapter 
on  that  subject. 

Transverse  Control.  In  practice,  the  lateral  stability  of  aero- 
planes is  maintained  by  four  different  methods:  (1)  automatically; 
(2)  by  warping;  (3)  by  balancing  planes,  i.  e.,  wing  tips  or  ailerons; 
(4)  by  "reefing,"  or  the  employment  of  supplementary  sliding  planes 
or  equalizers. 

At  present,  warping  the  planes  is  the  most  generally  employed 
and  most  practical  method,  but  it  is  expected  that  a  simple  method 
of  automatically  preserving  the  lateral  equilibrium  will  be  the  ulti- 
mate development,  and  many  designers,  including  the  Wright  Broth- 
ers, are  striving  for  that  end,  so  that  it  is  given  precedence  here. 

The  Voisin  is  the  only  type  for  which  automatic  stability  has 
been  claimed,  but  it  is  noticeable  that  in  later  types  of  this  machine, 
wing  tips  have  been  employed.  The  rear  box-cell  and  the  vertical 
keels  or  partitions  between  the  surfaces  of  the  main  planes  exert  such 
a  forcible  "hold"  on  the  air  that  to  displace  the  machine  is  difficult  and, 
in  all  ordinary  turmoils  of  the  air,  it  displays  exceptional  stability. 
In  fact,  a  well-known  aviator  amusingly  stated  at  Rheims  that,  were 
a  Voisin  tipped  completely  over  on  one  end,  it  would  still  be  aero- 
dynamically  supported,  so  great  is  the  expanse  of  vertical  surface. 

Without  such  keels,  however,  the  lateral  balance  of  an  aeroplane 
is  so  precarious  that  some  form  of  control  is  absolutely  necessary. 
The  method  of  warping  the  planes  in  connection  with  the  operation 
of  the  vertical  or  direction  rudder  is  the  chief  claim  of  the  Wright 
patents,  and  all  machines  employing  it  are  essentially  the  same  as  the 
Wright  device,  even  though  the  operating  connections  do  not  con- 
trol the  main  planes  and  the  rudder  simultaneously.  In  addition 
to  the  biplanes  employing  it,  all  the  successful  monoplane  types, 
except  the  Pfitzner,  depend  upon  warping  the  main  planes  for  this 
control. 

Because  of  the  structural  difficulty  of  rigidly  bracing  the  surface 
of  a  monoplane,  warping  is  an  ideal  form  of  control.  But  the  rigid 
structure  of  the  biplane  permits  auxiliary  planes  to  be  more  easily 
provided.  This  is  done  in  the  Curtiss,  Farman,  Sommer,  the  recent 


261 


66  TYPES   OF    AEROPLANES 

Voisin,  and  the  Cody.  Both  these  methods  of  transverse  control 
are  very  efficacious,  but  the  additional  resistance,  unaccompanied 
by  any  increase  of  lift,  which  is  produced  by  balancing  planes,  ren- 
ders them  less  desirable  than  warping.  On  the  other  hand,  there 
are  objections  to  weakening  the  structure  of  the  main  surfaces  by 
making  them  movable. 

There  is  a  further  distinction  between  these  two  methods  of 
control,  which,  although  not  thoroughly  understood  in  a  general 
sense,  appears  to  be  borne  out  in  practice,  viz,  when  a  plane  is 
warped  the  action  tends  not  only  to  tip  the  machine  up  on  one  side 
but  also,  due  to  the  helical  form  thus  assumed,  to  turn,  which  can 
be  counteracted  only  by  the  vertical  rudder.  In  the  case  of  wing 
tips,  however,  due  to  the  equal  but  contrary  position  in  which  they 
are  placed,  both  sides  of  the  machine  are  equally  retarded  and,  in 
addition,  since  the  main  surfaces  preserve  the  same  shape  and  the 
same  angle  of  incidence,  this  tendency  to  turn  appears  to  be  absent. 
Curtiss  states  that  to  correct  for  tipping  alone,  he  makes  no  use  of 
the  vertical  rudder. 

Sliding  panels,  or  "equalizers,"  as  applied  to  the  Pfitzner  mono- 
plane, represent  one  of  the  recently-designed  methods  of  transverse 
control  which  are  considered  not  to  infringe  the  Wright  patents. 
This  system  has  not  been  adequately  tried  out  as  yet,  but  there 
appears  to  be  no  reason  why  it  should  not  be  as  effective  as  either 
the  system  of  warping  or  the  use  of  wing  tips.  There  are  many 
other  methods  designed  to  give  transverse  control  and  it  seems  at 
present  that  they  are  all  equally  reliable.  Structural  individualities 
of  the  types  of  aeroplanes  will  persist,  in  all  likelihood,  so  that  we 
can  not  picture  the  machine  of  the  future  with  any  one  form  of  trans- 
verse controlling  apparatus.  Balancing  planes  and  wTing  tips,  or 
ailerons,  are  widely  used  at  present,  but  further  progress  in  aerody- 
namics is  likely  to  show  that  warping  is  better,  particularly  as  the 
development  of  improved  forms  of  construction  and  more  suitable 
materials  eliminate  the  objection  of  weakening  the  main  structure 
as  now  built. 

Aspect  Ratio.  It  is  at  once  observable  from  the  values  given 
that  the  ratio  of  spread  to  depth  (aspect  ratio)  of  the  monoplanes  is 
generally  less  than  that  of  the  biplanes.  This  interesting  fact  is  due 
very  likely  to  the  structural  difficulty  of  making  the  wing  of  a  mono- 


263 


TYPES   OF   AEROPLANES  67 

plane  long  and  narrow,  and  at  the  same  time  providing  the  neces- 
sary strength  without  involving  undue  weight.  The  Antoinette 
monoplane  has  recently  shown  a  departure  from  this  standard  by 
decreasing  the  depth  and  increasing  the  spread,  thus  increasing  the 
aspect  ratio,  but  the  framework  had  to  be  greatly  strengthened.  The 
new  model  Voisin  has  the  highest  aspect  ratio  of  the  types  consid- 
ered here,  but  exhibits  no  remarkable  qualities  therefrom. 

Both  theoretically  and  experimentally  the  value  of  this  quality 
is  considered  to  have  much  to  do  with  the  ratio  of  lift  to  drift;  but 
whether  or  not  in  actual  practice  those  machines  like  the  Santos- 
Dumont,  having  as  low  an  aspect  ratio  as  3  to  1,  are  really  inferior 
in  their  qualities  of  dynamic  support  to  a  machine  like  the  Cody 
with  as  high  an  aspect  ratio  as  7  to  1,  is  difficult  to  determine,  since 
so  many  other  factors,  such  as  the  loading  and  velocity,  are  involved. 
It  is  interesting  to  note  here  that  some  of  the  large  soaring  birds, 
such  as  the  albatross,  may  be  considered  as  aeroplanes  of  very  high 
aspect  ratio.  The  effect  of  aspect  ratio  upon  speed  is  not  discern- 
ible upon  comparing  the  types. 

Greater  stability,  however,  is  commonly  supposed  to  result 
from  a  high  aspect  ratio,  because  of  the  decreased  proportionate 
movement  of  the  center  of  pressure.  A  further  advantage  is  that 
the  higher  the  aspect  ratio  of  a  plane,  the  lower  is  the  angle  giving 
the  maximum  ratio  of  lift  to  drift,  and  consequently  for  given  speed 
and  loading  less  power  is  necessary.  There  appears  to  be  little 
question  but  that  the  development  of  aeroplane  construction  of  the 
near  future  will  tend  toward  an  increase  in  the  aspect  ratio  to  as 
high,  possibly,  as  12  to  1. 

Incident  Angle.  The  angle  that  the  main  supporting  surfaces 
of  an  aeroplane  make  with  the  horizontal  line  of  flight  is  termed 
the  incident  angle,  and  it  is  something  that  at  present  varies  greatly 
in  the  different  types.  The  Wright  biplane  is  notable  for  its  very 
low  angle  of  incidence  in  flight,  rarely  exceeding  two  degrees. 

Renard,  after  deductions  from  the  experiments  of  Borda,  Lang- 
ley,  and  other  investigators,  has  enunciated  the  principle  that,  as 
the  incident  angle  diminishes,  the  driving  power  expended  in  sustaining 
a  given  plane  in  the  air  also  diminishes.  Wilbur  Wright  states  that, 
the  angle  of  incidence  is  fi.xed  by  the  area,  weight,  and  speed  alone.  It 
varies  directly  as  ths  weight,  and  inversely  as  the  area  and  speed,  although 


263 


68  TYPES   OF   AEROPLANES 

not  in  exact  ratio.  Faraud  concludes  that  small  angles  are  the 
most  efficient  for  all  aeroplanes.  There  is  for  each  type  a  most 
efficient  angle  of  incidence,  or  point  where  the  power  expended  for 
flight  is  least.  In  flying,  the  incidence  should  be  kept  constant  at 
this  angle  in  order  to  obtain  the  highest  speed. 

The  Farman,  Voisin,  Bleriot  XI,  Grade,  and  Sommer  have  an 
angle  of  incidence  when  first  starting  much  greater  than  when  in 
flight.  Since  this  involves  greater  drift  resistance  and  consequently 
more  power  necessary  to  attain  the  velocity  of  levitation  and,  further- 
more, as  aeroplanes  with  as  heavy  a  loading  but  without  an  excessive 
angle  are  able  to  rise  after  a  reasonably  short  run,  it  would  appear 
as  if  this  provision  were  unnecessary. 

Recent  experiments  in  aerodynamics  indicate  that  the  ratio 
of  lift  to  drift,  with  a  surface  of  the  shape  now  so  generally  used,  varies 
little  between  the  values  of  2  degrees  and  6  degrees,  a  maximum 
value  being  reached  in  the  neighborhood  of  3  degrees.  This  explains 
in  a  measure  the  wide  variations  in  this  angle  as  observed  and  recorded 
for  the  different  types,  and  also  that  many  of  the  present  machines 
preserve  their  equilibrium  during  comparatively  large  changes  of 
their  longitudinal  inclination. 

In  general,  the  incident  angle  of  the  monoplanes  is  greater  than 
that  of  the  biplanes.  The  most  common  angle  is  in  the  neighbor- 
hood of  5  to  7  degrees.  But  in  the  Bleriot  XII,  an  incident  angle 
of  12  to  13  degrees  is  often  used  in  flight.  Incidence  will  very  likely 
be  established  purely  by  the  lift-drift  ratio  of  a  plane,  and  the 
angle  kept  as  constant  as  possible  to  give  this  its  highest  value. 

Propellers.  With  one  or  two  exceptions,  aeroplanes  of  all 
types  are  driven  by  a  single,  high-speed  screw.  The  Wright  and 
the  Cody  are  the  only  instances  of  machines  provided  with  two 
propellers  rotating  in  opposite  directions.  The  greater  efficiency 
of  a  propeller  of  large  diameter  revolving  at  a  slow  speed  over  one 
of  small  diameter  and  high  rotative  speed  has  attracted  much  atten- 
tion. This  seems  to  be  borne  out  especially  in  the  case  of  the  Wright 
machine,  in  which  more  thrust  is  obtained  per  unit  of  power  than 
in  any  other  type.  The  limit  of  rotative  speed  in  practice  is  approx- 
imately 1,500  r.  p.  m.,  and  in  all  types  excepting  the  Wright,  Cody, 
and  Bleriot  XII,  the  r.  p.  m.  rate  exceeds  1,000.  Many  of  the  aero- 
planes, more  particularly  those  of  foreign  design,  use  the  Chauviere 


264 


TYPES   OF   AEROPLANES  69 

wood  propellers,  for  which  an  efficiency  of  80  per  cent  is  claimed. 
The  Antoinette,  Grade,  and  Voisin,  use  metal  screws. 

The  thrust  and  efficiency  of  the  various  propellers  are  about 
the  same  for  equal  sizes,  and  although  the  theory  of  propeller  design 
is  very  little  understood  as  yet,  the  experimental  methods  used  have 
resulted  in  the  design  of  propellers  of  as  good  efficiency  or  higher 
efficiency  than  those  used  in  marine  practice.  The  position  of  the 
propeller  in  front  in  most  of  the  monoplanes  is  largely  a  matter  of 
convenience  of  design,  although  it  has  an  advantage  in  that  the 
swiftly  moving  mass  of  air  thrown  backward  by  the  screw  also 
exerts  an  added  lift  when  thrown  back  on  the  plane.  At  the  same 
time,  however,  this  action  also  increases  the  resistance,  but  as  the 
frame  resistance  of  the  monoplane  is  much  less  than  that  of  the 
biplane,  the  propeller  may  be  placed  in  front  without  any  very  seri- 
ous consequences.  The  Voisin  (tractor  type)  biplane  has  the  screw 
in  front,  but  the  results  obtained  indicate  that  this  is  detrimental  to 
the  speed. 

It  is  generally  believed  by  aviators  that  much  better  results 
could  be  obtained  by  the  use  of  propellers  15  to  20  feet  in  diameter, 
rotating  slowly.  But  there  are  two  disadvantages  involved  in  this 
feature  of  construction  which  make  its  adoption  in  the  machines  of 
the  future  rather  doubtful.  The  first  is  the  greatly  added  weight 
of  so  large  a  propeller  and  the  second  is  that  of  building  a  good 
chassis  high  enough  to  permit  of  the  propeller  rotating  freely. 

Rudders.  The  direction  rudder  in  all  types,  except  the  Pfitzner, 
is  placed  at  the  rear.  The  Cody  biplane  has  an  additional  direction 
rudder  in  front.  All  the  monoplanes,  with  the  exception  of  the  Pfitz- 
ner, have  their  elevating  rudders  at  the  rear,  while  in  all  the  biplanes, 
except  the  new  Wright  and  more  recent  Voisin  models,  this  rudder 
is  placed  out  in  front.  Rudders  placed  at  the  rear  are  advantageous 
in  that  they  act  at  the  same  time  as  keels.  But,  in  general,  the  plac- 
ing of  the  elevating  rudder  in  front  seems  to  offer  more  exact  con- 
trol of  the  longitudinal  stability. 

The  elevating  rudder  almost  always  exerts  some  supporting 
power.  Therefore,  when  placed  in  front  and  turned  up  for  ascent, 
the  support  is  increased,  as  it  naturally  should  be.  But  when  this 
rudder  is  placed  at  the  rear,  the  movement  for  ascent  is  such  that 
the  supporting  power  of  the  rudder  is  decreased,  making  it  of  nega- 


265 


70  TYPES   OF   AEROPLANES 

live  value,  so  that  instead  of  causing  the  front  of  the  machine  to 
rise,  it  causes  the  rear  to  sink.  Following  the  same  theory  shows 
that  when  the  elevating  rudder  is  out  in  front,  in  starting,  the  front 
of  the  machine  lifts  off  the  ground  and  is  strongly  followed  by  the 
body;  while  if  this  rudder  be  in  the  rear,  when  turned  to  give  ascent 
the  rear  merely  sinks  more,  and  not  only  is  the  run  greatly  increased, 
but  the  power  required  and  the  risks  incurred  ar^  greater.  That  it 
is  generally  so  used  on  the  monoplanes  is  the  result  of  necessity  due 
to  the  propeller  being  at  the  front. 

In  the  Wright  biplane  the  elevating  rudder  is  so  constructed 
that  when  elevated  it  is  automatically  warped  concavely  on  the 
under  side,  and  when  depressed,  curved  in  the  opposite  way.  This 
materially  adds  to  the  rudder's  force  due  to  the  peculiar  law  of 
aerodynamics  whereby  a  curved  surface,  under  the  same  conditions 
as  a  flat  surface,  has  a  greater  ratio  of  lift  to  drift.  The  reduction  in 
the  size  of  the  rudder  is  thus  made  possible  and  its  flat  shape  when 
normal  greatly  reduces  the  head  resistance.  In  so  far  as  a  biplane 
is  usually  supposed  to  cause  interference  of  the  two  surfaces  and 
greater  head  resistance,  it  would  appear  as  if  the  biplane  rudders 
as  used  on  the  Wright  and  the  Curtiss  were  not  as  efficient  as  single 
planes,  but  the  structural  advantages  of  this  arrangement  are  impor- 
tant. 

The  method  employed  by  Grade  of  merely  bending  flexible 
surfaces,  instead  of  turning  rigid  movable  planes,  has  a  great  advan- 
tage in  that  the  rudders,  after  being  used,  spring  back  to  their  normal 
position.  This  method  has  not  been  adopted  on  any  other  type, 
however,  although  it  has  many  considerations  of  safety  favoring  it. 

In  almost  all  of  the  successful  aeroplanes,  with  the  possible 
exception  of  the  Wright  and  Antoinette,  it  is  conceded  that  the 
size  of  the  rudders  is  much  too  great.  This  is  clearly  indicated  by 
the  remarkably  small  change  of  inclination  usually  necessary  for  a 
change  of  direction.  This  ultra  sensitiveness  where,  as  in  some 
machines,  a  movement  of  a  few  hundredths  of  an  inch  will  consider- 
ably alter  the  state  of  equilibrium  of  the  machine,  is  certainly  unde- 
sirable. To  begin  with,  it  need  hardly  be  pointed  out  that  over- 
sensitiveness  of  a  rudder  usually  invites  dangerous  situations.  Fur- 
thermore, if  a  rudder  be  extremely  sensitive,  it  is  a  good  indication 
that  it  is  too  large,  in  which  case  it  is  absorbing  considerable  power 


266 


TYPES   OF   AEROPLANES  71 

that  could  be  put  to  better  use  elsewhere.  It  is  quite  likely,  there- 
fore, that  a  great  decrease  in  the  size  of  the  rudders  will  be  a  develop- 
ment of  the  near  future. 

Keels.  Keels  on  aeroplanes,  like  keels  on  a  boat,  add  greatly 
to  the  stability.  But  on  an  aeroplane  they  are  "dead  surfaces" 
and,  as  such,  have  the  disadvantage  of  offering  greater  expanse  of 
surface  for  wind  disturbance  to  act  upon.  They  unquestionably 
decrease  the  speed.  Tapering  keels,  such  as  those  employed  on  the 
Antoinette,  the  Pelterie,  and  the  latest  Bleriot  XI,  offer  a  maximum 
of  "entering  edge"  with  a  minimum  of  area,  and  for  that  reason  are 
more  advantageous  than  those  of  rectangular  form.  Keels  are 
entirely  lacking  in  the  original  Wright,  Santos-Dumont,  and  Cody, 
but  in  the  later  "headless"  Wright  two  small,  vertical  keels  of  semi- 
circular form  are  placed  in  the  angles  made  by  the  meeting  of  the 
skids  with  the  braces  from  the  latter  to  the  upper  main  plane,  while 
a  horizontal  keel  of  considerable  area  is  employed  in  the  rear  of  the 
Short  Wright  (English  manufacture). 

In  the  Voisin,  use  is  made  of  several  vertical  keels  of  large  area, 
really  partitions,  placed  not  only  in  the  rear  cell  but  also  between 
the  main  planes  themselves.  That  these  have  not  proved  entirely 
satisfactory  is  indicated  by  the  adoption  of  ailerons  to  maintain 
transverse  stability  in  the  more  recent  Voisin  machines.  Keels  add 
greatly  to  the  resistance  of  a  machine,  the  head  resistance  and  skin 
friction  with  their  consequent  power  absorption  being  considerable. 
It  is  generally  conceded  now  that  control  by  rudders  is  becoming 
so  perfected  that  any  inherent  stability  to  be  obtained  by  the  use 
of  keels  at  the  expense  of  power  is  hardly  worth  while.  No  special 
form  or  combination  of  keels,  so  far  designed  and  tried,  have  really 
succeeded  in  giving  any  kind  of  complete  inherent  stability. 

Actual  practice,  however,  demonstrates  that  they  do  increase 
stability,  tending  to  hold  the  machine  to  its  course,  and  keels  at  the 
rear  of  a  machine  somewhat  on  the  order  of  a  bird's  tail  are  found 
advantageous,  so  that  it  is  quite  unlikely  that  they  will  disappear  as 
a  feature  of  aeroplane  design  for  years  to  come. 

Mounting.  This  is  the  only  remaining  detail  of  construction 
that  need  be  considered  in  this  connection.  There  is  probably  no 
other  single  feature  in  which  the  various  machines  differ  more  widely, 
nor  any  other  in  which  such  totally  different  provision,  or  the  absence 


867 


72  TYPES   OF   AEROPLANES 

of  it,  for  absorbing  the  shocks  of  landing,  proves  so  uniformly  suc- 
cessful. When  an  aeroplane  drops  as  a  dead  weight  for  even  a  short 
distance,  it  suffers  considerable  damage  regardless  of  the  presence 
of  shock  absorbers  or  otherwise,  whereas,  in  ordinary  use,  it  appears 
to  be  as  easy  to  land  lightly  with  a  machine  having  a  rigid  chassis, 
as  with  one  in  which  elaborate  precaution  is  taken  to  guard  against 
shocks. 

There  is  another  factor  to  be  guarded  against,  however,  and 
that  is  the  gyroscopic  action  developed  by  the  swiftly  revolving  pro- 
peller, which  tends  to  resist  a  sudden  change  of  its  plane  of  rotation, 
as  well  as  all  vibration.  If,  therefore,  when  running  over  the  ground 
the  machine  be  suddenly  jarred,  the  propeller  is  likely  to  snap  off. 
This  has  been  experienced  by  M.  Bleriot  on  more  than  one  occasion, 
and  he  emphasizes  the  necessity  of  providing  springs  on  a  heavy 
machine  mounted  on  wheels. 

Three  distinctive  methods  of  mounting  have  been  employed 
to  date: 

(1)  Using  skids  only,  as  in  the  original  Wright  machine.     This  is 
already   obsolete,  as  it  involved  the   use   of   special    starting 
apparatus. 

(2)  Wheels  only,  as  in  the  Curtiss,  Voisin  (both  types),  Bleriot  (both 
types),  Pelterie,  Grade,  and  Pfitzner. 

(3)  Wheels    and    skids    combined  —  Farman,    Antoinette,    Santos- 
Dumont,  Cody,  Sommer,  and  later  Wright  machines. 

Details  of  some  of  the  most  important  designs  are  given  in 
Fig.  40. 

The  relative  merits  of  mounting  on  wheels  only  or  skids  and 
wheels  constitute  a  subject  of  wide  discussion.  Where  the  former 
are  employed  independently,  the  addition  of  a  brake  is  almost  indis- 
pensable to  bring  the  machine  to  a  quick  stop  wThere  the  landing 
area  is  restricted;  whereas,  with  a  skid  forming  part  of  the  support, 
as  in  the  Antoinette,  the  latter  acts  as  a  brake.  Of  course,  it  per- 
forms the  same  office  in  starting,  to  the  detriment  of  a  quick  rise  from 
the  ground.  The  extra  power  required  on  that  account,  however, 
is  not  very  great,  as  the  skid,  supporting  only  the  tail,  does  not  carry 
any  great  weight.  It  is  consequently  not  very  efficient  as  a  brake 
either,  so  that  provision  of  the  latter  class  on  all  types  should  be  made. 


268 


TYPES   OF   AEROPLANES 


73 


Fig.  40.     Types  of  Landing  Skids  for  Aeroplanes 


269 


74  TYPES   OF   AEROPLANES 

A  number  of  combinations  of  skids  and  wheels  have  been  tried, 
such  as  that  of  the  new  Wright  which  starts  on  its  four  wheels,  and 
lands  on  the  skids  to  which  they  are  attached.  The  Sommer  and 
Farman  are  typical  examples  of  this  combined  form  of  mounting, 
and  experience  in  their  use  appears  to  demonstrate  that  they  are  the 
most  effective  for  heavy  machines.  On  light  aeroplanes,  such  as  the 
Curtiss  and  the  Grade,  where  the  loading  is  reasonably  light,  spring 
mountings  have  been  found  unnecessary,  the  wheels  alone  taking  the 
shock  of  landing.  No  skids  are  employed.  The  more  recent  Curtiss 
machines  are  provided  with  an  efficient  brake.  It  is  quite  likely, 
however,  that  the  high  speed  aeroplane  of  the  future  will  not  only 
be  provided  with  an  elastic  mounting,  but  when  regular  stations  are 
established,  means  will  be  employed  for  projecting  it  from  some 
ingenious  starting  device  at  high  velocity,  so  that  it  may  be  quickly 
launched  into  the  air. 

Speed.  It  is  generally  conceded  that  the  chief  object  of  the 
aeroplane  designer  at  present  is  to  increase  the  speed,  prophecies 
of  100  miles  per  hour,  and  considerably  more,  being  not  at  all  uncom- 
mon. Whether  this  can  be  attained  or  not  is  a  question  that  only 
the  future  can  solve,  but  a  comparison  of  the  speeds  prevailing  in 
January,  1910,  and  December,  1910,  shows  such  a  marked  increase 
for  the  development  of  a  single  year  that  this  does  not  appear  to  be 
beyond  the  possibilities  of  the  future,  by  any  means.  It  must  be 
borne  in  mind,  of  course,  that  while  resistance  increases  as  the  square 
of  the  speed,  the  power  to  overcome  it  must  increase  as  the  cube. 
This  would  seem  to  make  the  attainment  of  the  100-mile  mark 
something  that  would  involve  considerable  modification  of  the 
present  type  of  aeroplane,  in  order  to  attain  increased  efficiency, 
as  the  goal  in  view  is  not  to  be  won  by  a  mere  increase  of  power. 

The  speed  shows  no  direct  variation  with  aspect  ratio  or  load- 
ing, and  higher  speeds  seem  to  be  merely  attained  by  an  excess  of 
power,  a  decrease  of  head  resistance,  and  a  small  supporting  surface. 
In  Table  I  are  given  the  speeds  of  the  various  types  described, 
i.  e.,  those  of  which  they  had  been  shown  capable  up  to  January, 
1910. 

Flight.  In  the  manner  of  flight  of  the  different  types,  pro- 
nounced distinctions  may  be  drawn.  Probably  the  widest  variation 
in  this  respect  exists  between  the  Wright  and  the  earlier  Voisin 


270 


TYPES   OF   AEROPLANES 


75 


TABLE  I 
Speed   Data 


Type 

Miles 
per 
hour 

Type 

Miles 
per 
hour 

Bleriot  XI  (Racing  Type) 

63 

Farman  (Racing  Type) 

44 

Santos-Dumont 

55 

Sommer  (1910  Model) 

44 

Bleriot  XI  Bis(1910  Model) 

51 

Wright  (Rear  Control) 

43 

Antoinette  (1910  Model) 

50 

Wright  (19  10  Model) 

41 

Voisin  (Racing  Type) 

49 

Farman  (1910  Model) 

41 

Curtiss 

48 

Voisin  (1910  Model) 

40 

Bleriot  XII  (1910  Model) 

48 

Farman  (Passenger  Type) 

39 

Bleriot  XI  2  Bis 

48 

Pelterie 

39 

Pfitzner 

45 

Cody 

37 

Grade 

44 

with  numerous  vertical  keels.  The  flight  of  the  latter  may  be  best 
described  as  "sluggish."  The  enormous  resistance  of  this  machine 
appears  to  hold  it  back  very  perceptibly,  while  in  making  turns  its 
action  is  slow  and  "deadened."  In  sharp  contrast  to  this  is  the 
strikingly  active  flight  of  the  Wright  machine.  Its  resistance  is 
very  small  for  a  biplane  and  its  movement  through  the  air  is  quick 
and  precise,  particularly  when  compared  with  the  flight  of  the 
Farman  biplane,  the  sluggish  movements  of  which  at  the  Inter- 
national Meet  near  New  York  earned  for  it  the  sobriquet  of  "the 
ice- wagon."  In  changing  direction  or  warping  to  maintain  lateral 
stability,  the  action  of  the  Wright  is  precise  and  almost  instantane- 
ous, the  Wright  biprane  answering  its  helm  in  a  remarkably  quick 
and  effective  manner. 

In  grace  of  form  and  swiftness  of  flight  the  Antoinette  and 
Bleriot  monoplanes  are  a  delight  to  the  eye.  They  appear  to  move 
through  the  air  without  the  slightest  effort  and  at  the  distance  of 
a  mile  or  so  give  the  impression  of  being  huge,  soaring  birds,  so 
steady  and  perfectly  under  control  is  their  every  movement.  Due 
to  the  smooth  whirring  of  their  multi-cylindered  motors,  this  is 
accentuated  when  close  at  hand,  in  comparison  with  the  clattering 
exhaust  of  the  four-cylinder  Wright  engine,  which  many  uninitiated 
spectators  mistake  for  a  noise  made  by  the  propellers,  the  turning 
of  which  is  plainly  visible  owing  to  their  low  speed. 

The  Curtiss  in  flight  is  noticeable  for  its  constant  rising  and 


271 


76 


TYPES   OF   AEROPLANES 


TABLE  II 
Characteristics  of  Different  Types 


Machine 

Pounds  per 
h.  p. 

Pounds  per 
sq.  ft. 

Speed  in  Still 
Air,  m.  p.  h. 

Wright 

41 

2.05 

41 

Wright  (r.  c.) 

37 

2.50 

43 

Farman  (pssgr) 

34 

3.15 

39 

Bleriot  XI 

29 

4.50 

51 

Antoinette 

27 

3.33 

50 

Pelterie 

27 

4.40 

39 

Cody 

25 

2.57 

37 

Farman  ('10) 

24 

2.80 

41 

Pfitzner 

24 

3.20 

45 

Curtiss  (pssgr) 

22.6 

3.64 

Voisin  ('10) 

22.5 

3.14 

40 

Curtiss 

22 

2.50 

48 

Farman  (rcg) 

21 

3.00 

44 

Bleriot  XII 

21 

5.30 

48 

Bleriot  XI  2 

19.8 

3.68 

48 

Voisin  (rcg) 

19.5 

3.27 

49 

Voisin  (tractor) 

19 

2.36 

40 

Grade 

17 

2.00 

44 

Sommer 

16 

2.76 

44 

Sommer  (rcg) 

15 

3.25 

Santos-Dumont 

12 

3.10 

55 

Bleriot  XI  (rcg) 

7.5 

5.76 

63 

falling,  tracing  a  sinuous,  vertical  path  through  the  air,  in  contrast 
with  the  perfectly  even  and  level  keel  maintained  by  most  of  the 
other  machines.  In  making  any  comparison  of  flight,  however,  the 
personal  equation  also  must  be  considered,  as  the  action  of  the 
machine  is  largely  governed  by  the  skill  of  the  aviator.  In  the  present 
instance,  however,  the  impressions  recorded  were  of  the  different 
machines  in  the  hands  of  skillful  pilots,  all  of  whom  had  been  flying 
for  a  year  or  more  and  had  made  a  great  many  flights.  The  Santos- 
Dumont  was  early  dubbed  the  "clown"  of  the  International  Meet 
and  its  appearance  was  invariably  the  signal  for  a  roar  of  amused 
applause.  Despite  its  speed,  its  erratic  action  marked  by  continual 
dips  and  violent  rocking,  always  seemed  to  have  it  on  the  verge  of 
tumbling  to  the  ground.  Because  of  its  light  loading,  the  Grade 
seems  especially  buoyant  in  the  air.  The  other  types  mentioned 
show  characteristics  between  the  extreme  sluggishness  of  the  Voisin 
and  Farman  and  the  remarkable  preciseness  of  the  Wright. 


272 


TYPES   OF  AEROPLANES  77 

As  the  question  of  duration  of  flight  depends  much  more  upon 
the  skill  of  the  aviator,  the  endurance  of  the  motor,  and  the  amount 
of  fuel  carried  than  it  does  on  the  machine  itself,  a  comparison  of  the 
longest  flights  made  by  each  type  would  be  valueless. 

Efficiency.  One  of  the  best  indications  of  the  general  efficiency 
of  an  aeroplane  is  the  amount  of  weight  carried  per  horse-power, 
but  it  will  be  apparent  that  this  must  also  be  considered  in  connec- 
tion with  the  weight  lifted  per  square  foot  of  lifting  surface,  its  speed, 
and  similar  factors.  The  first  of  these  mentioned  is  usually  termed 
' 'pounds  per  horse-power"  and  is  obtained  by  dividing  the  total  weight 
of  the  machine  in  flight  by  the  horse-power  of  the  motor.  This  is 
a  variable  owing  to  the  different  weights  of  the  aviators,  but  not  one 
of  sufficient  importance  to  record  in  the  case  of  a  one-man  machine. 
At  the  time  Table  II  was  compiled  (January,  1910),  the  Bleriot  XI 
(racing  model)  appeared  to  be  the  most  wasteful  of  power,  while 
the  Wright  was  the  most  efficient,  this  still  being  true  of  the  latter. 
It  must  also  be  borne  in  mind  that  the  Bleriot  is  a  very  much 
faster  machine  than  the  Wright.  Table  II  summarizes  the  various 
characteristics  of  the  different  types. 


273 


TYPES  OF  AEROPLANES 

PART  II 


SPECIAL  TYPES 

As  explained  under  the  head  of  "Standard  Types/'  this  designa- 
tion is  not  intended  to  cover  aeroplanes  that  can  properly  be  regarded 
as  standardized  in  the  usual  acceptance  of  that  term,  although  with 
one  or  two  exceptions  they  are  built  along  essentially  the  same  lines 
in  their  respective  classes.  In  addition  to  the  machines  described 
in  that  category,  there  are  hundreds  of  others  which  do  not  differ 
sufficiently  from  these  types  to  merit  reference.  Besides  these,  how- 
ever, there  are  some  aeroplanes  which  are  distinguished  by  radical 
departures  from  the  accepted  standards  in  question,  or  which  have 
been  designed  for  some  special  form  of  service,  and  no  work  on  the 
the  subject  would  be  complete  without  at  least  a  brief  description 
of  their  distinctive  features.  All  of  these  machines  are  of  more 
recent  construction  and,  as  they  are  being  brought  out  in  rapid  suc- 
cession as  the  art  develops,  those  given  here  naturally  include  only 
a  limited  number. 

Paulhan  Trussed  Type.  The  most  radical  departure  noted  up 
to  the  present  writing  is  a  machine  constructed  for  Paulhan,  Fig.  41, 
in  which  by  reason  of  utilizing  tetrahedral  surfaces  similar  to  those 
of  the  well-known  kites  invented  by  Alexander  Graham  Bell,  neither 
warping  nor  ailerons  are  required  to  maintain  lateral  stability.  The 
planes  of  the  Paulhan  machine  are  built  upon  a  form  of  trussed  girder 
made  up  of  two  long,  thin  ash  planks  about  8  inches  wide  near 
their  central  section,  and  about  |  inch  thick,  the  general  plan  upon 
which  the  biplane  is  constructed  being  similar  to  the  Curtiss  machine. 
There  is  a  central  section  containing  the  motor  and  the  aviator's 
seat,  the  outer  sections  being  attached  to  this  central  section 
in  a  novel  manner.  The  planks  in  question  are  spaced  about 
8  inches  apart  and  the  lower  one  curves  upward  toward  its  ends  until 
it  meets  the  upper  one.  These  two  planks  are  tied  together  by  a 
series  of  flat,  steel  plates  forming  a  series  of  V's,  thus  forming  a  very 

Copyright,  1912,  by  American  School  of  Correspondence. 


275 


80  TYPES   OF   AEROPLANES 

rigid  trussed  girder  that  eliminates  the  necessity  of  using  the  numer- 
ous guy  wires  ordinarily  employed.  The  ribs  are  attached  to  the 
lower  members  of  these  main  girders  by  means  of  clamps  passing 
over  an  armored  wood  fillet  that  lies  within  the  base  of  every  other 
V.  The  ribs  are  cut  out  of  solid  wood  and  are  arched  to  the  proper 
curve.  The  cloth  is  provided  with  pockets  which  enable  it  to  be 
slipped  on  the  ribs  and  laced  in  place.  As  the  ribs  are  attached  to 
the  girders  at  their  front  ends  only,  they  have  a  certain  amount  of 
spring  or  flexibility  which,  it  is  claimed,  gives  the  machine  a  high 
degree  of  inherent  stability. 

Both  the  lower  and  upper  girders  are  divided  into  sections  and 
connected  by  uprights.  The  uprights  of  adjoining  sections  are 
placed  side  by  side  and  fastened  together  by  S-shaped  leather  straps 
which  wrap  around  them  and  are  drawn  taut  by  a  special  fastener. 


Fig.  41.     Paulhan-Fabre  Biplane  with  Tetrahedral  Cell  Girder  Framing 

Leather  straps  are  also  used  to  connect  the  uprights  of  the  center  cell 
to  the  chassis  as  well  as  in  most  other  parts  of  the  machine  where 
joints  must  be  made.  Except  for  its  tendency  to  stretch,  leather 
affords  a  very  strong  and  tough  material  for  this  purpose,  while  its 
use  avoids  the  necessity  of  piercing  holes  in  the  struts.  It  is  ideal  for 
a  machine  like  the  Paulhan  biplane  here  described  and  the  Fabre 
monoplane,  along  the  lines  of  which  the  former  is  constructed,  as  both 
are  intended  to  be  demountable  in  order  to  make  them  readily 
portable. 

There  are  two  long,  trussed  girders  running  from  the  front  of 
the  lower  plane  out  to  the  rear,  where  they  support  the  single-surface 


276 


TYPES   OF   AEROPLANES  81 

tail  and  the  vertical  rudder  in  front  of  it,  while  at  the  front  they 
carry  the  monoplane  horizontal  rudder,  or  elevator.  The  motor  is 
on  a  frame  back  of  the  pilot's  seat  which  is  located  in  a  torpedo- 
shaped  aluminum  car  secured  to  the  lower  plane  simply  by  crossed 
guy  wires  that  run  through  it  at  the  front.  The  car  and  frame  are 
one  and  besides  the  50-horse-power  Gnome  motor  they  carry  a  large 
tank  for  gasoline  just  behind  the  aviator  and  passenger's  seats  which 
are  in  tandem.  The  aluminum  car  is  employed  to  protect  the  aviator 
and  to  reduce  head  resistance,  the  fore-and-aft  girders  having  their 
sides  covered  with  cloth  for  the  same  purpose.  The  machine  is 
mounted  on  two  skids  placed  beneath  these  two  fore-and-aft  girders, 
each  skid  being  carried  on  a  pair  of  pneumatic-tired  wheels  connected 
by  a  short  axle  which  is  attached  to  the  skid  by  a  rubber  band  and 
is  guyed  fore  and  aft  to  keep  it  from  twisting. 

In  place  of  the  single-control  lever  to  which  he  has  become 
accustomed  in  piloting  the  Farman  machine,  Paulhan  uses  a  vertical 
steering  wheel  similar  to  that  originated  by  Curtiss.  Pushing  or 
pulling  on  this  wheel  turns  the  horizontal  rudder  downward  or  upward, 
while  turning  the  wheel  operates  the  vertical  rudder  at  the  rear.  No 
method  of  warping  the  wings  or  other  device  for  correcting  side  tip- 
ping was  shown  on  this  machine  when  it  was  exhibited  at  the  1910 
Paris  show,  and  it  is  claimed  that  the  flexible  ribs  in  connection  with 
the  zigzag-girder  construction  give  the  machine  sufficient  -transverse 
stability  to  make  any  provision  of  this  nature  unnecessary.  The 
machine  has  been  flown  successfully  and  proved  remarkably  steady 
in  flight,  from  which  it  is  evident  that  the  means  at  present  in  use  of 
maintaining  lateral  stability  mark  only  the  first  steps  toward  what 
may  be  eventually  accomplished  in  this  direction. 

In  addition  to  this  important  feature,  the  chief  claim  made  for 
the  machine  is  the  rapidity  with  which  it  may  be  assembled  or 
demounted.  The  end  cells  may  be  detached  by  taking  out  three 
bolts  at  the  top  and  bottom  of  the  uprights,  an  operation  that  requires 
only  a  minute  or  two  at  the  outside,  while  the  whole  machine  may  be 
taken  apart  and  packed  in  a  case  15|  feet  long  by  3J  feet  square, 
within  an  hour.  The  ready  detachability  of  the  end  cells  makes  it 
possible  to  store  the  machine  in  an  ordinary  shed,  as  the  total  spread 
of  38  feet  is  reduced  to  12  or  15  feet  when  these  sections  have  been 
removed.  The  fore-and-aft  length  of  this  new  biplane  is  25|  feet 


277 


82  TYPES   OF   AEROPLANES 

and,  including  the  horizontal  rudder  and  the  tail,  the  area  is  300 
square  feet.  The  total  weight  of  the  machine  itself  is  800  pounds, 
which  is  low,  considering  its  size  and  heavy  construction. 

M.  Fabre,  designer  of  the  hydroaeroplane  described  later,  is 
also  responsible  for  the  construction  of  this  Paulhan  biplane,  and 
makes  the  following  claims  for  his  system:  Great  strength  and 
rigidity;  small  head  resistance;  absence  of  trussing  wires  with  their 
liability  to  loosen  or  break  and  their  considerable  head  resistance; 
automatic  transverse  stability  due  to  the  zigzag  girders  resembling 
tetrahedral  cells — the  most  stable  form  of  supporting  surface;  and 
its  ready  portability. 

In  view  of  the  supporting  power  and  stabilizing  effect  of  the 
trussed  girders,  it  is  interesting  to  note  that,  assuming  the  machine's 
critical  speed  to  be  45  miles  an  hour  with  the  cloth  planes  in  place, 
the  girders  would  support  its  800  pounds  of  weight  alone  were  the 
speed  increased  to  120  miles  an  hour.  If  it  were  possible  to  reef  the 
cloth  of  the  wings  while  in  flight,  it  would,  therefore,  be  possible  to 
keep  diminishing  the  supporting  surface  until  this  consisted  of  the 
girders  alone,  while  the  speed  would  increase  to  120  miles  an  hour, 
or  more. 

Three  years  ago,  Santos-Dumont  constructed  a  small  biplane 
having  its  supporting  surfaces  set  at  a  sharp  dihedral  angle.  Wood 
was  used  for  the  aeroplane  surfaces,  and  it  was  thought  the  machine 
would  be  very  speedy.  However,  the  supporting  surface  was  so 
small  in  proportion  to  the  weight  that  it  was  difficult  to  attain  suf- 
ficient speed  for  a  sustained  flight,  and  almost  at  the  first  attempt 
the  machine  was  smashed  and  abandoned.  The  Paulhan  biplane 
with  reefed  surfaces  would  be  an  almost  direct  descendant  of  Santos- 
Dumont's  wood-surfaced  flyer,  and  the  possibility  of  a  machine  flying 
under  bare  poles,  so  to  speak,  would  give  an  idea  of  what  might  be 
accomplished  in  the  future.  The  promise  of  the  "reefing  aeroplane," 
as  it  may  be  termed,  is  being  seriously  considered  and  will  be  treated 
later  in  this  article. 

Nieuport  Monoplane.  More  than  ordinary  interest  attaches 
to  the  Xieuport  monoplane,  as,  while  it  does  not  differ  radically  in 
design  from  the  majority  of  French  monoplanes,  it  is  not  only  the 
simplest  but  likewise  the  most  efficient  type  thus  far  produced  and 
it  is  to  be  greatly  regretted  that  its  creator,  Edouard  Nieuport,  should 


378 


TYPES   OF   AEROPLANES  83 

have  met  an  untimely  death  in  an  accident,  as  the  great  success  of 
his  efforts  in  the  two  years  that  he  devoted  himself  to  aviation  pre- 
saged greater  and  more  important  developments.  During  1911, 
the  Nieuport  monoplane  earned  for  itself  the  title  of  the  "fastest 
aeroplane."  Weyman's  100-horse-power  Nieuport  made  an  average 
of  78  miles  per  hour  in  the  Gordon-Bennett,  winning  the  trophy  for 
America,  while  a  30-horse-power  machine  of  the  same  make  made 
58.9  miles  per  hour  in  the  same  event.  What  this  means  may  best 
be  realized  from  the  fact  that  the  original  Wright  biplane  with  a  motor 
of  the  same  rating  could  not  do  better  than  40  miles  per  hour.  A 
70-horse-power  Nieuport  has  mads  74.8  miles  per  hour,  as  com- 
pared with  the  speed  of  61  miles  per  hour  made  with  the  100-horse- 
power  Bleriot  which  won  the  1910  Gordon-Bennett.  In  the  French 
military  competition,  Weyman's  100-horse-power  Nieuport  averaged 
72.6  miles  per  hour  for  186  miles  with  three  people. 

The  construction  of  the  Nieuport  type  for  two  persons,  fitted 
with  a  Gnome  50-horse-power  revolving  motor  is  as  follows: 

The  wings  are  built  up  on  two  main  spars  of  ash,  while  be- 
tween these  spars  are  run  three  light  battens  merely  to  tie  the 
ribs  together.  The  ribs,  of  which  there  are  13,  are  of  l-section,  built 
in  the  usual  manner  and  with  the  webs  perforated  to  save  weight, 
while  the  box  ribs  are  built  up  by  using  two  webs  and  larger  top  and 
bottom  flanges.  The  rib  curve  varies  in  each  rib,  decreasing  toward 
the  wing  tips  and  going  down  to  a  flat  bow.  The  wing  section  given 
in  the  sketch,  Fig.  42i  might  be  taken  as  the  standard  curve,  allow- 
ance being  made  for  the  different  chord  at  various  places,  and  also 
for  the  different  thicknesses  of  the  spar,  which  tapers  both  ways 
from  a  straight  central  portion.  It  will  be  noted  that  there  is  a  slight 
reverse  curve  on  the  under  surface  at  the  trailing  edge,  while  it  is  very 
pronounced  on  the  upper  surface.  Each  wing  is  trussed  with  two 
heavy  standard  cables,  top  and  bottom,  to  each  spar,  and  they  are 
set  at  a  slight  dihedral  angle.  The  fuselage  longitudinals  are  also  of 
ash,  rectangular  in  section,  and  channeled  out  between  the  struts  to 
achieve  lightness.  Rectangular  ash  struts  are  also  employed,  except 
those  for  the  skids,  which  are  steel  tubing.  Connection  between 
struts  and  longitudinal  members  is  made  by  aluminum  castings  to 
which  the  wire  bracing  is  anchored.  The  entire  structure  is  covered 

rwith  fabric. 

j 


279 


Fig.  42.     Details  of  Nicuport  Monoplane 


280 


TYPES   OF  AEROPLANES  85 

Control  is  by  means  of  a  single  hand  lever,  operating  the  rudder 
and  elevating  plane,  while  a  bar  for  the  feet  works  the  warping 
mechanism.  This  single  hand  lever  is  mounted  by  a  swivel  joint 
on  a  short  shaft  lying  along  the  floor  inside  the  body.  A  forward 
and  backward  movement  of  this  lever  operates  the  elevator  by  wires 
passing  around  pulleys  mounted  at  the  ends  of  the  rocking  shaft, 
while  a  lateral  movement  of  the  lever  actuates  the  rudder  wires 
through  a  crank  formed  by  an  extension  of  the  rear  pulley  sheave 
which  is  fixed  to  the  rock  shaft.  The  elevators  are  semicircular 
in  plan,  and  are  constructed  of  steel  tubing  frames  covered  with 
fabric  on  both  sides,  the  tail  or  fixed  plane  also  being  built  of  steel 
tubing,  while  nothing  but  steel  is  employed  in  the  construction  of 
the  running  gear,  the  central  skid,  the  axle  which  is  made  of  a  single, 


Fig.  43.      Mieuport  Running  Gear 
I 

five-leaf  s  pring,  and  the  oval  skid  struts.  The  V-members  are  made 
up  as  a  unit  and  can  be  slipped  over  the  skid  and  put  in  place  in  a 
short  time  should  repairs  be  necessary.  The  extreme  simplicity  of 
this  running  gear  is  apparent  at  a  glance,  Fig.  43.  The  power  plant 
is  a  50-horse-power  Gnome  motor,  driving  a  two-bladed  propeller 
8  feet  4  inches  in  diameter.  The  span  is  36  feet,  the  wings  having 
an  extreme  width  of  8  feet  If  inches,  where  they  are  joined  to  the 
fuselage,  and  tapering  to  5  feet  5J  inches  at  their  outer  ends,  the 
total  area  of  the  main  planes  being  221  square  feet,  while  the  tail  or 
fixed  rear  plane  of  semicircular  form,  placed  8  feet  7|  inches  back 
of  the  wings,  has  an  area  of  30  feet,  and  the  elevators,  which  are 
practically  part  of  the  tail,  being  hinged  to  it,  have  a  spread  of  13J 
square  feet.  This  makes  a  total  area  of  274J  square  feet,  which  on  a 


281 


86  TYPES   OF   AEROPLANES 

total  weight  of  715  pounds,  exclusive  of  the  aviator,  gives  a  loading 
of  2J  pounds,  or  of  3i  pounds  with  the  pilot,  assuming  the  latter's 
weight  to  be  170  pounds,  as  is  customary.  The  overall  length,  exclu- 
sive of  the  propeller  shaft,  is  25  feet  4  inches. 

Bleriot  Limousine.  The  Bleriot  Limousine,  Fig.  44,  is  a  novel 
aeroplane  that  marks  an  advance  in  development,  as  it  is  the,  first 
to  appear  with  a  closed  body  for  the  passengers.  The  aviator  sits 
forward  and  outside  of  the  body,  the  resemblance  to  a  cab  thus  caused 
having  also  earned  for  it  the  name  of  the  "aerial  taxi."  This  machine 
was  built  by  Bleriot  to  the  order  of  M.  Henri  Deutsch,  who  has 
probably  done  more  for  aviation  in  France  than  any  other  single 
individual.  In  general  design,  this  machine  somewhat  resembles 


Fig.  44.     Bleriot  Limousine  or  Aerial  Taxicab 

the  original  Bleriot  XII  and,  like  the  first  passenger-carrying  machines 
turned  out  by  this  maker,  the  passengers  are  seated  in  the  center 
below  the  main  plane.  In  all  other  respects,  however,  it  is  different, 
and  appears  to  constitute  more  or  less  of  a  reversion  to  the  original 
Wright  type,  the  horizontal  being  placed  some  distance  out  in  front, 
while  a  stabilizing  plane  and  the  direction  rudder  mounted  over  it, 
are  carried  some  distance  behind  the  main  planes.  The  power  plant 
is  a  100-horse-power,  fourteen-cylinder  Gnome  revolving  motor, 
and  it  is  mounted  at  the  rear  of  the  main  plane,  instead  of  at  the 
front,  the  fuel  being  carried  in  a  torpedo-shaped  tank  above  the  roof 
of  the  cab  and  just  in  front  of  the  motor.  Control  is  by  the  usual 
Bleriot  method,  consisting  of  a  universally-mounted  post  having 
an  aluminum  bell  at  the  bottom  to  which  the  control  cables  are 


882 


TYPES   OF   AEROPLANES  87 

fastened.  Complete,  but  without  any  passengers  or  the  aviator, 
the  machine  weighs  1,540  pounds,  and  it  has  a  supporting  surface 
of  430J  square  feet,  triple  heavy  rubber  bands  being  employed 
as  shock  absorbers  on  the  chassis,  to  sustain  the  unusual  weight. 
The  spread  of  the  main  plane  is  43  feet,  and  the  overall  length  of 
the  machine  is  46  feet.  Although  it  would  seem  that  the  twenty  odd 
square  feet  of  surface  presented  head  to  the  wind  by  the  front  wall 
of  the  body  would  cause  a  seriously  detrimental  head  resistance,  the 
machine  has  flown  very  successfully,  showing  itself  to  be  capable  of 
carrying  two  passengers,  besides  the  aviator,  at  a  rate  of  50  miles 
per  hour.  The  seats  in  the  body  are  fitted  with  pneumatic  cushions 
to  take  up  the  shock  in  case  the  machine  alights  heavily.  A  speaking 
tube  is  provided,  so  that  the  passengers  can  communicate  with  the 
aviator.  This  is  the  first  time  that  a  machine  has  been  built  and 
flown  in  which  special  care  wTas  taken  to  construct  it  with  a  comfort- 
able body  for  the  carrying  of  passengers,  and  it  is  doubtless  the  fore- 
runner of  many  more  of  a  similar  type  that  will  make  their  appear- 
ance in  the  next  few  years. 

Tatin=Paulhan  Aerial  Torpedo.  M.  Victor  Tatin,  who  is 
responsible  for  the  design  of  this  extremely  novel-looking  aeroplane, 
has  waited  twenty  years  to  see  his  ideals  realized.  He  originally 
designed  the  machine  about  1890,  and  has  argued  for  the  correctness 
of  its  lines  in  several  brochures  and  books  published  in  the  interval, 
though  the  machine  itself  was  not  built  until  the  latter  part  of  1911. 
The  body  is  completely  enclosed  from  end  to  end  and  reveals  a  fine 
example  of  the  pisciform  shape  recommended  by  Renard  for  the 
dirigible.  The  propeller  is  placed  at  the  extreme  rear  and  the 
direction  rudder  is  placed  just  above  the  elevator,  a  few  feet  forward 
of  the  propeller,  so  that  without  the  wings  the  resemblance  to  a  fish 
is  striking,  while  the  upturned  outer  ends  of  the  main  planes  give  it 
the  appearance  of  a  large  soaring  bird.  This  upcurving  of  the  wings 
is  said  to  provide  stability  to  an  extent  that  makes  wing  warping 
unnecessary,  while  the  torpedo-shaped  body  cuts  the  head  resistance 
down  to  a  minimum.  The  machine  is  provided  with  a  flat  tail,  the 
rear  part  of  which  is  movable  and  forms  the  horizontal  rudder.  The 
pilot's  seat  is  located  in  the  body  just  forward  of  the  wings,  and  the 
50-horse-power  Gnome  motor  is  placed  just  back  of  the  pilot  in  a 
special  compartment.  The  chief  peculiarity  of  the  design  is  the 


283 


88  TYPES   OF  AEROPLANES 

placing  of  the  propeller  at  the  extreme  rear,  instead  of  forward  as  is 
usual  in  monoplanes.  Drive  is  by  means  of  a  long,  universally- 
jointed  shaft  running  back  from  the  motor  and  carried  in  five 
bearings  supported  by  piano-wire  guys.  The  chassis  consists  of  two 
wood  beams  bent  in  semi-elliptic  form  and  connected  at  the  lower 
part  by  an  axle  fitted  with  shock  absorbers  and  carrying  two  pneu- 
matic-tired wheels. 

Bleriot  Racer.  That  increased  speed  is  largely  a  matter  of 
refinement  of  detail  based  upon  experience  is  evident  from  the  1911 
Bleriot  racer,  which  has  developed  a  speed  of  81  miles  per  hour  with 
50  horse-power,  its  designer  having  taken  advantage  of  the  lessons 
taught  by  the  several  long-distance  European  aeroplane  races,  most 
of  which  were  won  by  Bleriot  machines.  To  reduce  head  resistance, 
the  upper  flat  cross  member  of  the  usual  Bleriot  chassis  has  been 
placed  below  instead  of  on  top  of  the  body.  This  results  in  short- 
ening the  steel  tube  uprights.  The  body  has  been  made  extremely 
narrow  at  the  front,  while  at  the  rear  it  flattens  completely,  termi- 
nating in  an  absolutely  flat  horizontal  rudder.  The  extreme  front 
end  narrows  down  to  not  quite  a  foot  in  width,  though  ample  space 
is  allowed  for  the  aviator,  while  a  long  aluminum  hood  covers  the 
tanks  and  motor  and  prevents  the  usual  spray  of  oil  in  the  aviator's 
face.  The  usual  running  gear  and  shock  absorbers  are  placed  forward, 
while  the  bamboo  skid  is  at  the  extreme  rear  end  of  the  fuselage. 
Beside  the  usual  simple  V-shaped  support  for  attaching  the  bracing 
wires  of  the  wings,  the  bracing  tubes  below  are  employed  and  they 
have  been  made  considerably  longer  besides  being  well  guyed  to  the 
body.  They  carry  the  warping  mechanism  at  their  lower  ends  and 
this  has  been  modified  in  some  ways.  The  vertical  rudder  has  the 
outline  of  a  shark's  fin  and  is  carried  on  top  of  the  tail,  as  in  the 
Bleriot  XII. 

This  is  the  twenty-seventh  different  model  that  Bleriot  has 
constructed.  It  has  a  span  of  23  feet,  an  overall  length  of  29  feet, 
and  a  supporting  surface  of  only  129  square  feet,  while  its  weight 
complete  is  948  pounds,  which  gives  the  unusually  high  loading  of 
7  pounds  per  square  foot. 

Bleriot  Canard.  In  contrast  with  the  Voisin  canard,  or  duck, 
as  an  aeroplane  with  the  aviator  in  front  in  a  covered  body  and  the 
motor  behind  has  come  to  be  known  in  France,  this  machine  is  a 


284 


TYPES   OF   AEROPLANES  89 

monoplane,  Fig.  45,  and  instead  of  being  new  is  a  revival  of  one 
of  Bleriot's  earliest  attempts.  Santos-Dumont  was  really  the  inventor 
of  this  type  of  machine  and  with  its  aid  he  was'  the  first  man  to  leave 
the  ground  in  a  power-driven  aeroplane  in  Europe.  The  new  Bleriot 
canard  is  much  shorter  than  the  Voisin,  its  thick,  short  body  pro- 
jecting forward  of  the  monoplane  wings  but  a  small  distance,  the 
horizontal  rudder  being  placed  at  the  tip  end  of  the  bow,  while  two 
tiny  vertical  rudders  on  top  of  the  main  plane  at  each  end  serve  to 
steer.  The  wings  are  guyed  to  an  inclined  rod  beneath,  which  extends 
forward  from  a  shoe  on  the  bottom  of  a  vertical  post.  Generous-sized, 
hinged  ailerons  are  employed  instead  of  warping  the  wings.  The 
running  gear  is  the  same  as  that  of  the  Nieuport,  while  the  span 
and  area  of  the  machine  are  identical  with  those  of  the  Bleriot  racer 


M 


Fig.  45.     Bleriot  Canard  Showing  Unique  Position  of  Engine  and  Propeller 

just  described,  the  total  overall  length  being  but  18  feet,  while  the 
weight  complete  with  a  50-horse-power  Gnome  motor  is  only  882 
pounds.  The  aviator's  seat  is  so  far  forward  that  it  would  seem  as 
if  he  ran  very  little  risk  of  being  injured  by  the  motor  in  case  of  a 
fall,  since  there  are  five  or  six  feet  of  stout  framing  between  the 
engine  and  the  pilot.  A  peculiarity  of  this  type  of  machine  is  that 
in  night  it  appears  to  be  going  backward. 

Antoinette  Armored  Monoplane.  Excess  weight  appears  to  have 
lost  all  its  terrors  for  the  designer  of  aeroplanes,  as  where  every  effort 
has  been  made  previously  to  reduce  this  to  the  absolute  working 
minimum,  the  builders  of  the  Antoinette  have  brought  out  a  machine 


285 


90  TYPES   OF   AEROPLANES 

in  which  the  most  vulnerable  parts,  such  as  the  motor  and  chassis, 
are  protected  by  armor  plate.  This  machine  was  designed  especially 
to  take  part  in  the  French  military  competition,  and  by  far  its  most 
important  feature  is  the  total  elimination  of  all  cross  wires,  struts, 
and  the  like.  Every  part  is  enclosed,  even  the  wheels  and  the  skids, 
with  the  result  that  the  head  resistance  is  greatly  decreased,  but  the 
weight  increased  still  further,  at  the  same  time  giving  the  machine 
a  most  peculiar  appearance.  In  addition,  a  peculiar  wing  section  is 
used,  flat  on  the  under  side  and  curved  on  the  upper.  Aerodynamical 
experiments  have  shown  this  type  of  wing  section  to  have  a  very 
bad  drift  resistance  at  low  angles  of  incidence  and  a  very  uniform 
rate  of  change  of  the  ratio  of  lift  to  drift  under  the  same  conditions. 
The  center  of  pressure  does  not  move  back  as  rapidly  as  on  other 
shapes,  as  the  angle  of  incidence  decreases  below  10  degrees.  This 
type  of  wing  is,  therefore,  more  stable  and  of  smaller  resistance.  The 
distribution  of  pressure,  however,  is  very  uneven,  but  because  of 
the  great  strength  of  the  planes  themselves  at  all  points,  this  is  not 
a  disadvantage.  The  wings  are  immensely  thick,  being  braced 
entirely  from  the  inside  and  measuring  over  two  feet  in  section 
where  they  join  the  body — something  altogether  without  precedent 
in  aeroplane  design.  Their  section  decreases  to  8  inches  at  the  wing 
tips.  The  shape  of  each  wing  is  trapezoidal  and  they  are  placed  at 
an  extreme  dihedral  angle.  This  adds  to  the  stability  of  the  machine 
in  a  calm,  but  in  gusty  winds  conditions  arise  where  a  large  dihedral 
angle  is  considered  by  many  to  be  extremely  dangerous.  The  boat- 
like  body  is  completely  enclosed  and  is  very  capacious.  The  motor 
of  the  regular  eight-cylinder  Antoinette  V-type,  of  100  horse-power, 
direct  connected  to  a  Normale  two-bladed  propeller,  is  placed  at  the 
extreme  forward  end,  while  the  aviator's  seat  is  in  the  body  at  a 
point  between  the  wings.  Though  equipped  with  a  100-horse-power 
motor,  the  machine  is  said  to  be  capable  of  flying  with  but  GO  horse- 
power. The  oddest  feature  of  this  type  is  the  landing  gear,  which  is 
entirely  enclosed  to  within  a  few  inches  of  the  ground.  There  are 
six  landing  wheels  forward,  three  on  each  side  of  the  center  and 
enclosed  in  what  is  termed  a  "skirt."  Two  smaller  wheels  are  placed 
at  the  rear.  The  dimensions  are:  Spread  52  J  feet,  length  overall  36 
feet,  width  of  wings  at  body  13  feet,  at  tips  9  feet,  area  of  supporting 
surface  602  square  feet,  total  weight,  including  aviator  and  fuel, 


286 


TYPES   OF   AEROPLANES  91 

2,400  pounds.  The  aviator  obtains  a  view  below  the  machine  through 
the  glass  floor  of  the  body  under  his  seat.  To  reduce  resistance  to  a 
minimum,  even  the  exhaust  pipes  of  the  motor  are  covered  with  a 
stream-line  design  shield.  This  type  is  of  an  immense  size  as  com- 
pared with  its  predecessors  and  is  very  bird-like  in  flight,  several 
successful  trials  having  been  made  with  it.  But  whether  the  great 
sacrifices  made  to  eliminate  projecting  spars  and  wires  are  wise, 
remains  to  be  seen.  The  machine  has  an  unusually  large  expanse 
of  vertical  surface  which  makes  it  difficult  to  handle  in  a  gusty  wind. 

Short  Two=Motor  Biplane.  Although  the  Gould  Scientific 
American  prize  of  $15,000  for  a  successful  two-motor  aeroplane  in 
which  either  motor  can  be  used  independently,  and  the  second 
started  in  mid  air  in  case  of  the  accidental  stoppage  of  the  other, 
has  now  been  open  for  almost  two  years,  there  have  been  few  attempts 
to  win  it.  A  Queen  monoplane  was  built  during  the  summer  of  1911 
for  this  purpose  and  fitted  with  two  50-horse-power  Gnome  motors, 
but  on  the  occasion  of  its  first  trial  it  came  to  grief.  M.  Legrand, 
the  French  engineer,  has  brought  out  a  racing  biplane  equipped  with 
two  100-horse-power,  fourteen-cy Under  Gnome  motors,  and  this 
machine  was  flown  successfully  by  Guillaume  at  Juvisy  in  October, 
1911.  The  Coanda  biplane,  entered  in  the  French  military  compe- 
tition, was  also  provided  with  two  motors  driving  the  propellers 
through  shafts  and  bevel  gearing.  The  Short  biplane,  equipped 
with  two  motors,  has  made  duration  flights  exceeding  one  hour,  so 
that  it  is  capable  of  ifulfilling  the  conditions  of  the  Gould  prize, 
though  not  eligible  for  the  latter  as  it  is  a  foreign  built  machine. 

In  general  outline  it  is  a  biplane  of  the  Farman  1910  type, 
equipped  with  two  50-horse-power  Gnome  revolving  motors,  placed 
centrally  and  one  in  front  of  the  other  in  the  rear  of  the  lower  main 
plane  at  either  end  of  a  nacelle  or  enclosed  body.  The  front  motor 
drives  two  propellers  in  opposite  directions  by  means  of  chains, 
precisely  as  on  the  Wright  biplane.  The  propellers  are  of  high  pitch, 
similar  to  the  Wright  type,  but  are  placed  in  front  of  the  main  cell, 
instead  of  behind  it.  The  rear  motor  drives  a  single  low-pitch  pro- 
peller at  high  speed  as  on  the  Farman  machines.  It  is  possible  to 
operate  either  motor  separately  or  both  together,  and  the  feasibility 
of  the  arrangement  has  been  well  proved  in  actual  flights.  The  rud- 
der and  aileron  controls  are  of  the  usual  Farman  type,  the  landing 


287 


92  TYPES   OF   AEROPLANES 

chassis  and  all  details  of  the  construction  having  been  made  specially 
strong  owing  to  the  extra  weight.  The  aviator  sits  in  the  enclosed 
body  and  there  is  a  seat  for  a  passenger  beside  him.  With  the 
immense  extra  power  available,  one  motor  sufficing  for  flight,  this 
type  has  the  ability  to  go  fast  or  slow,  and  with  its  full  100  horse- 
power can  climb  very  rapidly.  The  axes  of  the  front  propellers  and  the 
rear  one  are  not  on  the  same  level,  this  being  done  to  counterbalanca 
the  effect  on  the  tail  caused  by  the  draft  from  the  rear  propeller. 
As  soon  as  the  latter  ceases  to  operate  the  lifting  tail  sinks,  but  the 
higher  position  of  the  axis  of  thrust  of  the  forward  propellers  at  once 
overcomes  this.  The  dimensions  are:  Spread  34  feet,  chord  GJ  feet, 
supporting  area  435  square  feet,  weight  in  flight  2,000  pounds.  The 
speeds  are  said  to  range  from  35  to  50  miles  an  hour  depending  on 
whether  one  or  both  motors  are  operated. 

Dunne  Biplane.  This  is  a  machine  of  unusually  novel  type 
for  which  a  great  deal  is  claimed,  but  unlike  the  thousand  and  one 
machines  that  are  built  around  claims  and  do  not  get  much  further, 
the  Dunne  has  given  evidence  of  its  ability  to  do  what  its  inventor 
claims  for  it.  However,  it  is  put  forward  as  a  machine  in  which 
automatic  stability  has  been  achieved,  where,  as  a  matter  of  fact, 
the  design  is  one  possessed  of  an  unusually  high  degree  of  inherent 
stability,  there  being  no  devices  or  mechanism  to  give  automatic 
stability  in  the  sense  that  that  term  has  come  to  be  understood. 
Instead  of  having  the  main  planes  in  a  line  with  one  another,  they 
are  in  the  form  of  a  large  V  with  its  apex  forward,  so  that  while  the 
machine  is  tailless  in  that  there  are  no  supplementary  surfaces  of  the 
class  termed  tails  or  stabilizers,  the  ends  of  the  V  extend  so  far  back 
that  it  actually  has  two  tails  instead  of  one,  and  upon  this  fact  is 
based  much  of  its  ability  to  maintain  equilibrium.  The  official 
report  of  a  test  of  the  Dunne  witnessed  by  Orville  Wright  and  Griffith 
Brewer  in  December,  1911,  is  in  substance  as  follows: 

The  first  flight  was  over  a  distance  of  about  three  miles,  the  machine  being 
turned  at  a  height  of  about  100  feet  and  making  a  good  landing  near  the  start- 
ing point.  During  the  second  flight  of  2  minutes  29  seconds,  Mr.  Dunne 
made  notes  on  a  piece  of  paper  (involving  use  of  both  hands).  In  both  cases, 
the  engine  was  cut  off  in  the  air  before  landing  and  the  machine  came  down 
without  materially  altering  its  angle  of  incidence. 

A  resume  of  Dunne's  patent  will  serve  to  show  most  clearly  what 


288 


TYPES   OF   AEROPLANES  93 

his  aims  are  and  how  he  achieved  them,  reading  ''inherent"  instead 
of  "automatic"  stability.  The  patent  was  granted  early  in  1910 
in  England  and  covers  the  "curvature  and  shape  of  surfaces." 

The  object  of  the  invention  is  to  obtain  a  form  of  aeroplane  which  shall 
possess,  solely  by  the  form  and  arrangement  of  its  surfaces,  automatic  stability 
in  still  and  agitated  air,  and  freedom  from  oscillation.  The  inventor  has  found 
that  twisting  the  wings  of  an  aeroplane  involves  the  disadvantage  that  sections, 
either  longitudinal  or  transverse,  taken  across  the  wing  tip,  give  curves  that  are 
more  or  less  concave  on  their  upper  sides,  thus  failing  to  give  large  pressure 
reactions,  and  that  when  such  wings  are  twisted,  the  changes  brought  about 
in  the  pressures  by  the  concave  portions  are  so  abrupt  as  to  produce  unsteadi- 
ness, and  that  the  similar  concavity  on  the  transverse  section  produces  lateral 
instability.  The  two  essential  conditions  to  be  observed  are  to  decrease  grad- 
ually the  angles  of  the  fore-and-aft  cross  sections  of  the  wings  from  root  to  tip, 
without  producing  points  of  inflection  in  the  surfaces;  and  secondly,  to  main- 
tain considerable  differences  in  the  angles  of  the  inner  and  outer  portions  with- 
out too  much  loss  of  pressure  under  the  outer  portions.  The  present  invention 
consists  in  constructing  each  of  the  main  surfaces  as  a  rearwardly  projecting 
wing  whose  angle  of  incidence  decreases  from  the  root  to  the  tip,  and  by  shap- 
ing the  wings  so  as  to  compress  air  between  the  positively-inclined  portion  of 
the  wing  near  the  root  to  the  negatively-inclined  portion  near  the  tip.  The 
wings  must  be  so  sloped  backward  along  their  leading  edges  that  the  wing 
tip's  lie  behind  the  center  of  gravity  of  the  whole  aeroplane.  Further,  each 
wing  is  so  constructed  that  its  upper  face  is  formed  as  a  portion  of  a  cone  or  a 
cylinder,  the  angle  of  incidence  of  the  wings  decreasing  toward  the  tips,  and 
in  some  cases  changing  sign,  i.  e.,  negative  to  positive  angle,  or  vice  versa. 

The  principle  is  applicable  to  the  monoplane  quite  as  readily  as 
the  biplane,  one  of  the  former  type  of  Dunne  machines  having  been 
exhibited  at  the  Olyinipia  show  in  1911.  Like  its  prototype,  it  is 
designed  to  possess  natural  stability,  and  it  is  tailless  in  the  ordinary 
sense  of  the  term.  In  principle,  however,  the  V-plan  of  its  wings 
gives  it  two  tails  instead  of  one,  and  the  hinged  flaps  on  the  trailing 
extremities  of  its  wings  give  it  two  elevators  instead  of  one.  These 
flaps  are  under  independent  control,  and  serve  the  purpose  of  steer- 
ing the  machine  horizontally  and  vertically.  The  special  formation 
of  the  wings  already  referred  to  in  the  case  of  the  biplane,  is  likewise 
generated  on  the  surface  of  a  cone,  but  the  apex  of  the  cone  is  an 
entirely  different  place,  being  situated,  on  the  monoplane,  a  short 
distance  behind  the  trailing  extremity  of  the  wing  and  more  or  less 
directly  in  line  with  the  outside  edge.  This  formation  of  the  wing 
gives  a  variable  angle  of  incidence  from  shoulder  to  tip,  which,  in  con- 
junction with  the  V-plan  form,  confers  on  the  machine  the  principles 


289 


94  TYPES   OF   AEROPLANES 

of  the  fore-and-aft  dihedral  angle,  which  is  one  of  the  accepted  methods 
of  obtaining  natural  stability  and  is  a  characteristic  feature  in  the 
design  of  all  successful  aeroplanes.  Owing  to  the  wung  extremities 
being  situated  in  an  exposed  region  and  not  sheltered  behind  the  mid- 
dle portion  of  the  plane,  as  is  more  or  less  the  case  with  the  tail  of 
an  ordinary  aeroplane,  Dunne  claims  that  their  tail  effect  is  enhanced. 
Also  the  same  argument  applies  to  the  efficacy  of  the  dihedral  angle, 
because,  owing  to  the  formation  and  continuity  of  the  wings,  it  is 
impossible  to  define  what  part  constitutes  main  plane  and  what  part 
tail.  In  fact  the  relative  functions  of  these  members  are  per- 
formed by  different  parts  of  the  wings  in  accordance  with  the  require- 
ments of  the  moment. 

Lateral  stability  in  the  Dunne  monoplane  is  somewhat  more 
difficult  to  explain,  but  the  most  significant  feature  of  the  design  is 
unquestionably  the  fact  that  the  wing  formation  provides  down- 
turned  wing  tips,  as  distinct  from  the  upturned  wring  tips  on  several 
other  monoplanes,  all  of  which  are  designed  more  or  less  with  a  view 
to  natural  stability.  It  will  be  noticed,  of  course,  that  it  is  the  lead- 
ing edge  of  the  Dunne  monoplane  that  is  turned  down,  whereas  in 
the  Hadley,  Page,  and  Weiss  monoplanes,  it  is  turned  up,  so  that  the 
relative  positions  of  the  leading  and  trailing  edges  in  all  three  machines 
are  identical.  On  the  other  hand,  there  is  a  very  material  and  funda- 
mental difference  in  principle  between  the  two  methods,  for  whereas 
the  upturned  trailing  edge  represents  the  lateral  dihedral  angle,  the 
down-turned  leading  edge  represents  the  gull's  wing,  which  is  an 
accepted  method  of  obtaining  lateral  stability  in  side  gusts.  The 
general  action  is  as  follows: 

A  side  gust  ordinarily  lifts  that  side  of  the  machine  against  which 
it  first  strikes,  because  of  the  aeroplane  action  of  the  planes  consid- 
ered in  their  attitude  toward  the  gust  and  the  consequent  travel  of 
the  center  of  pressure  toward  the  leading  edge  facing  the  gust, 
which  involves  an  actual  travel  of  the  center  of  pressure  laterally  from 
the  real  center  of  gravity  of  the  machine.  Thus  the  machine  cants 
over  and  the  upset  is  emphasized  with  the  dihedral  angle,  because 
the  upturned  wing  offers  an  increasing  surface  for  normal  pressure. 
In  the  gull's  wing  method,  the  remoter  down-turned  wing  tip  pre- 
sents the  more  effective  surface  to  the  gust  and  tends  to  counteract 
the  lift  due  to  the  travel  of  the  center  of  pressure  on  the  remainder 


290 


TYPES   OF   AEROPLANES  95 

of  the  plane.  It  is,  in  principle,  little  more  or  less  than  the  idea 
which  was  tried  by  the  Wright  Brothers  in  some  of  their  early  glid- 
ing experiments.  Like  most  things  of  this  kind,  however,  there  was 
all  the  difference  between  the  broad  principle,  and  the  detail  of  carry- 
ing it  into  effect  on  a  practical  machine.  It  is  the  latter  that  makes 
the  Dunne  monoplane  such  an  original  monoplane. 

De  Marcay=Mooney  Monoplane.  In  this  machine  there  has 
been  materialized,  for  the  first  time,  a  practical  form  of  folding-wing 
construction.  Taking  advantage  of  the  system  of  construction 
developed  by  Bleriot  and  other  French  designers  in  their  monoplanes, 
each  wing  has  been  made  integral  together  with  its  supports  and  brac- 
ing guys,  the  design  otherwise  being  the  same  as  the  Bleriot  except 
as  necessarily  modified  to  meet  the  purpose  in  view.  Each  wing  is 
pivoted  at  its  point  of  attachment  to  the  body,  to  an  outward-sloping 
metal  upright  that  serves  as  a  mast  or  strut  from  which  the  bracing 
wires  are  strung,  in  addition  to  its  functions  as  a  hinge.  A  wheel 
alongside  the  driver's  seat  controls  the  position  of  these  wings,  and 
by  turning  it  the  change  is  effected  from  the  usual  full  spread  for 
flying  to  the  closed  position  over  the  body,  in  which  form  the  machine 
bears  a  most  striking  resemblance  to  a  huge  beetle.  In  both  posi- 
tions, there  is  provision  for  securely  locking  the  wings  in  place.  No 
attempt  has  been  made  to  permit  of  altering  the  position  of  the  wings 
in  flight,  the  novel  design  having  for  its  sole  purpose  the  more  com- 
pact stowing  of  the  wings  while  the  machine  is  on  the  ground,  to 
facilitate  storage  and  to  permit  of  its  being  driven  along  narrow  roads 
or  across  other  than  tlear  fields.  To  facilitate  the  latter  operation, 
the  wheels  of  the  landing  chassis  are  movable  and  can  be  controlled 
by  a  steering  gear  provided  for  the  purpose.  This  running  gear 
suggests  that  of  the  Breguet,  which  is  similarly  steerable  on  the 
ground,  and,  in  fact,  apart  from  the  folding  wing  feature,  the  machine 
is  along  conventional  French  lines.  Lateral  stability  is  obtained  by 
warping  the  wings  in  the  usual  manner,  while  the  tail  is  apparently 
a  blending  of  the  Xieuport  and  Bleriot  fan-tailed  designs.  The  fusel- 
age is  a  characteristic  four-car,  tapered-box  girder,  covered  with 
fabric  and  providing  seating  accommodation  for  the  driver  between 
the  wings.  Though  there  has  been  no  attempt  on  the  part  of  its 
makers  to  embody  this  improvement  in  the  present  machine,  it  has 
been  pointed  out  by  several  authorities  that  folding  the  wings  in  this 


291 


96  TYPES   OF   AEROPLANES 

manner  undoubtedly  approximates  the  means  employed  by  the  birds 
for  varying  speed,  and  that  when  it  is  discovered  how  to  apply  these 
in  a  practical  way,  without  longitudinal  shifting  of  the  center  of 
gravity,  the  long-desired  variable  speed  aeroplane  will  have  become 
a  reality. 

Variable  Speed  Aeroplanes.  As  at  present  designed,  every 
aeroplane  has  what  is  termed  its  critical  speed,  i.  e.,  the  rate  of  its 
travel  through  the  air  at  which  it  sustains  and  propels  itself  most 
efficiently.  In  many  designs  this  is  almost  a  fixed  factor,  i.  e.,  the 
aeroplane  can  not  sustain  itself  in  the  air  in  case  its  speed' falls  to 
any  extent  below  this  critical  point.  Take  the  old  type  Wright  biplane 
as  an  example.  This  had  a  speed  of  40  miles  per  hour,  but  its  stability 
became  precarious  at  35  miles  per  hour,  or  a  drop  of  slightly  over  10 
per  cent,  while  at  30  miles  per  hour,  it  probably  could  not  keep  to  the 
air  except  by  making  dives  and  thus  taking  advantage  of  the  accelera- 
tion of  gravity.  With  the  greatly-increased  speeds  that  have  been 
obtained  with  the  aeroplane,  a  variable-speed  type  is  more  to  be 
desired  than  ever,  as  a  landing,  to  be  safe,  must  be  made  at  low  speed. 
Probably  one  of  the  greatest  variations  in  speed  shown  by  an  aero- 
plane thus  far  is  that  of  Bleriot's  100-horse-power  racer  which  won 
the  Gordon-Bennett  trophy  at  Belmont  Park  in  1910,  at  an  average 
speed  of  practically  70  miles  per  hour,  but  which  started  and  alighted 
at  50  miles  per  hour.  It  is  not  always  possible  to  select  safe  land- 
ing places,  particularly  when  compelled  to  alight,  and  the  danger  of 
landing  increases  with  the  velocity.  A  substantial  prize  has  accord- 
ingly been  offered  by  the  Marquis  de  Dion,  through  L' Auto  (Paris) 
for  aeroplanes  which  can  travel  over  a  given  course  with  the  greatest 
variation  in  speed.  To  a  degree,  the  Breguet  monoplane  meets 
these  conditions,  as  it  can  vary  its  speed  greatly  by  changing  the 
angle  of  incidence  of  its  sustaining  surfaces.  As  yet,  however,  this 
has  not  been  developed  to  a  point  where  the  change  can  be  made 
during  a  flight,  so  that  unless  the  Breguet  is  permitted  to  change  its 
angle  of  incidence  between  trials,  it  will  not  possess  any  advantage 
over  the  machines  with  fixed  wings.  According  to  aeroplane  con- 
structors, the  minimum  speed  on  striking  the  ground  with  the  motor 
stopped,  is  three  fourths  of  the  starting  velocity.  For  the  Bleriot 
this  would  be  37  miles  per  hour.-  The  disastrous  effects  of  striking 
a  slight  elevation  of  ground  at  such  a  speed  and  with  a  vertical  velocity 


292 


TYPES   OF   AEROPLANES  97 

of  10  or  12  feet  per  second,  may  easily  be  imagined,  and  the  danger 
increases  with  the  size  of  the  machine.  The  further  development  of 
the  aeroplane  depends  largely  upon  the  successful  provision  of  a 
factor  of  safety  in  this  respect.  There  is,  of  course,  a  great  tempta- 
tion to  employ  a  water  surface  for  landing,  if  possible,  as  this  is  not 
only  level  but  it  forms  an  admirable  buffer  against  shocks.  More- 
over, a  large  aeroplane  can  be  mounted  more  conveniently  on  rigidly 
connected  floats  than  on  wheels  and  springs.  But  with  this  construc- 
tion it  would  be  also  necessary  to  rise  from  the  water,  starting  at  the 
low  speed  at  which  the  propeller  could  drive  the  craft  when  afloat. 

In  order  to  combine  high  maximum  speed  with  low  speed  in 
starting  and  landing,  and  for  emergencies,  the  inclination  of  the 
sustaining  surfaces  must  be  capable  of  variation,  so  that  the  speed 
can  be  varied  greatly  while  the  axis  of  the  machine  remains  horizontal, 
and  the  propeller  must  be  designed  to  work  with  maximum  power 
and  efficiency,  using  the  full  power  of  the  motor  at  all  speeds  of  the 
aeroplane,  for  in  starting,  especially  from  the  water,  full  power  must 
be  employed.  An  aeroplane  propeller  driven  by  a  constant  speed 
motor  exerts  a  maximum  thrust  when  its  blades  have  a  definite 
inclination,  which  varies  with  the  speed  of  the  aeroplane.  For  the 
purpose  of  automatically  adjusting  the  propeller  blades  to  the  angle 
of  maximum  thrust  at  every  speed,  flexible  blades  are  employed  by 
Breguet,  a  centrifugal  governor  by  Capon,  and  an  electric  regulator 
by  Reister-Picard.  The  devices  of  Breguet  and  Capon  are  simple, 
but  only  approximately  solve  the  problem;  while  that  of  Reister- 
Picard  is  perfect  in  theory,  but  complicated  and  delicate  in  practice. 

Breguet.  Breguet's  original  flexible  blade  was  formed  of  rubber 
cloth  stretched  over  a  series  of  flat  steel  springs,  which  were  attached 
at  one  end  to  the  rigid  front  edge  of  the  blade,  but  the  construction 
was  afterward  simplified  by  adopting  a  rigid  blade,  capable  of  motion 
around  its  edge,  and  controlled  by  a  single  spring.  Breguet  has 
carried  six  persons  in  an  aeroplane  fitted  with  a  propeller  of  this  type, 
driven  by  a  50-horse-power  motor,  and  has  since  developed  a  three- 
bladed,  flexible  type  which  promises  even  better  results.  In  this, 
each  blade  is  attached  to  the  shaft  by  an  arm,  and  is  free  to  oscillate, 
under  the  control  of  springs,  about  three  axes.  At  starting  the  blade 
turns  on  its  axis  so  as  to  strike  the  air  at  a  very  small  angle  and  pro- 
duce a  maximum  thrust.  As  the  aeroplane  gains  speed  the  blade 


293 


98  TYPES   OF   AEROPLANES 

returns  toward  its  normal  position,  and  thereafter  automatically 
adapts  its  inclination  approximately  to  the  speed  of  the  aeroplane. 
The  blade  protects  itself  against  the  irregularities  of  the  motor  by 
turning  slightly  in  its  plane  of  rotation  about  its  point  of  attachment 
to  the  arm,  and  also  by  rocking  backward  and  forward. 

Capon.  Capon's  system  of  regulating  the  inclination  of  the 
propeller  blades  by  means  of  a  centrifugal  governor  is  very  simple 
in  theory  and  construction ;  but  the  inclination  of  the  blades  is  con- 
trolled entirely  by  the  speed  of  the  motor,  and  is-  not  affected  by  the 
speed  of  the  aeroplane,  unless  the  former  is  made  to  depend  upon 
the  latter  by  another  regulator.  This  is  not  the  usual  practice,  nor 
is  it  desirable,  as  the  efficiency  of  the  internal  combustion  motor  is 
impaired  by  alterations  of  its  normal  speed. 

Reister-Picard.  In  Reister-Picard's  system,  each  of  the  two 
blades  of  the  propeller  is  attached  to  an  arm  which  can  be  turned 
on  its  axis  by  a  crank  connected  through  a  linkage  to  a  spring- 
controlled  sliding  collar  on  the  propeller  shaft.  This  collar  is  in  turn 
connected  to  a  hand  lever  by  means  of  which  the  pilot  can  alter  the 
angle  of  inclination  of  the  propeller  blades  to  give  the  maximum 
thrust,  as  determined  by  the  reading  of  a  pressure  gauge  in  front  of 
him.  This  gauge  communicates  with  a  small  annular  vessel  filled  with 
lubricating  oil  and  fitted  with  a  piston  so  as  to  put  pressure  on  the 
oil.  This  vessel  is  directly  back  of  a  bearing  next  to  the  collar,  so 
that  it  gives  a  visible  indication  of  what  the  propeller  is  doing  at 
any  moment.  The  same  result  can  also  be  obtained  automatically 
by  means  of  an  electric  solenoid  and  plunger,  the  circuit  of  which  is 
made  and  broken  by  a  spring  piston  in  a  small  oil  cylinder  communi- 
cating with  the  main  oil  chamber  already  referred  to.  In  action,  the 
coil  of  the  solenoid  would  be  intermittently  energized  by  currents 
traversing  it  first  in  one  direction  and  then  the  other,  which  would 
tend  to  maintain  the  thrust  at  its  maximum  value,  but,  like  auto- 
matic stability  devices  of  a  similar  nature,  the  apparatus  is  too  delicate 
to  form  a  practical  adjunct  to  the  aeroplane  in  its  present  state  of 
development.  Reister-Picard  has  also  designed  an  aeroplane  in  which 
the  inclination  of  the  sustaining  surfaces  can  be  varied.  This  is 
practically  a  double  biplane,  Fig.  46,  having  a  biplane  elevator  E 
forward  and  a  vertical  rudder  G  at  the  stern.  The  two  biplanes 
are  connected  by  a  braced  girder  P,  which  serves  to  support  the 


294 


TYPES   OF   AEROPLANES 


99 


power  plant  and  its  accessories.  The  four  slightly  arched  sustaining 
surfaces  X  are  capable  of  rotation  on  transverse  horizontal  axes  Y. 
M  is  the  motor,  R  the  fuel  tank,  and  C  the  mechanic's  seat,  L  being 
the  lever  by  which  he  can  control  the  inclination  of  the  propeller 
blades  if  their  automatic  regulation  becomes  deranged.  S  is  the  seat 
of  the  pilot  who  operates  the  rudders  and  also  varies  the  inclination 
cf  the  sustaining  surfaces  by  turning  the  wheel  T.  The  mean  incli- 
nation of  these  surfaces  to  the  horizon,  as  they  are  drawn  in  the 
figure,  is  about  15  degrees,  but  their  inclination  can  be  diminished 
to  5  degrees  as  indicated  by  the  dotted  line  w,  for  soaring  at  very 
high  speed,  and  increased  to  30  degrees,  as  indicated  by  K,  for 
landing.  In  starting  from  rest  on  the  ground  or  water,  the  surfaces 
are  set  as  nearly  level  as  possible.  When  sufficient  velocity  has  been 
attained,  the  angle  is  suddenly  shifted  to  15  degrees,  and  the  aero- 


Fig.  46.     Reister-Picard    Double    Biplane   with    Provision   for   Inclining   the 
Supporting  Planes 

plane  rises  without  falling  upon  the  full  power  of  its  motor,  as  is 
the  usual  practice.  The  inclination  of  the  sustaining  surfaces  is  then 
gradually  diminished  and  the  power  increased  by  operating  the 
throttle  until  the  maximum  power  is  being  developed.  At  this  time, 
the  inclination  of  the  sustaining  surfaces  is  about  7  degrees  and  the 
aeroplane  has  attained  its  normal  speed.  In  landing,  the  inclination 
is  gradually  increased  to  15  degrees,  while  the  power  is  diminished, 
the  motor  being  stopped  just  before  the  ground  is  struck  and  the 
inclination  is  then  suddenly  increased  to  the  full  30  degrees,  enor- 
mously increasing  the  head  resistance  and  bringing  the  aeroplane  to 
a  stop  in  a  very  short  distance. 

Etrich  Bird=Wing  Monoplane.     The  Etrich  monoplane  is  the 
result  of  a  lengthy  study  of  bird-wing  structure,  Etrich  beginning 


295 


100  TYPES   OF   AEROPLANES 

his  experiments  in  1898  by  acquiring  the  Lilienthal  glider.  He  made 
extensive  studies  of  the  propulsive  organs  of  every  form  of  flying 
animal,  birds,  insects,  bats,  the  flying  fish,  even  extending  his  investi- 
gations to  the  vegetable  kingdom  by  studying  the  various  forms  of 
flying  seeds,  such  as  those  of  the  sycamore  and  the  pine. 

The  wings  of  the  Etrich  monoplane  are  what  he  terms  of  the 
"zanonia"  form,  and  were  previously  tried  out  very  thoroughly  in 
a  glider,  the  experiments  with  the  latter  dating  from  1904.  As  will 
be  apparent  in  Fig.  47,  the  front  part  of  each  wing  is  rigidly  con- 
structed of  webbed  ribs,  built  over  three  longitudinal  spars,  of  w'  ich 
the  forward  one  forms  the  leading  edge.  These  sections  are  double 
surfaced,  i.  e.,  covered  on  both  sides  with  a  rubberized  fabric.  Behind 
the  rear  beam  extend  bamboo  continuations  of  the  ribs  which  are 
covered  with  a  single  surface  of  fabric  and  form  a  flexible  trailing 
edge.  The  flexible  wing  tips  are  turned  up  at  the  rear  within  and 
so  give  both  wings  an  effective  negative  angle  of  incidence.  It  is  to 
this  feature  that  the  Etrich  owres  its  pronounced  degree  of  inherent 
stability.  Lateral  balance  is  maintained  by  raising  either  wing  tip 
by  means  of  a  cable,  which,  passing  over  a  pulley  situated  at  the 
top  of  the  king  post,  divides  up  into  eight  wires  connected  to  the 
flexible  extremities  of  the  wing.  A  cable  passing  over  the  lower  end 
of  the  king-post  lowers  the  opposite*  tip  a  corresponding  amount. 
Enormous  strength  is  imparted  to  the  wing  by  a  bridge-like  structure 
of  steel  tubing,  which  embraces  the  middle- wing  spar  and  is  attached 
below  the  under  surface,  which  renders  the  wings  capable  of  with- 
standing strains  many  times  in  excess  of  those  they  are  likely  to  be 
called  upon  to  bear  in  flight. 

A  small  wheel  mounted  at  the  lower  extremity  of  the  king-post 
protects  the  wing  tip  from  contact  with  the  ground.  The  bird  tail 
pivots  in  one  unit  about  a  horizontal  axis,  the  rear  portion  of  this 
tail  forming  the  elevator,  which  is  controlled  by  warping  the  horizontal 
tail  plane.  Two  small,  triangular  vertical  rudders,  one  above  and  the 
other  below  the  horizontal  tail  plane,  are  hinged  to  the  rear  edges  of 
two  triangular  stabilizing  fins  and  are  operated  by  pedals  in  front  of 
the  pilot's  seat,  these  being  plainly  apparent  in  the  plan  view  of  the 
machine,  Fig.  47.  Elevation  and  lateral  balance  are  controlled  by 
a  rotable  hand  wheel  placed  on  the  top  of  a  vertical  column.  The 
chassis  is  similar  to  that  of  the  Bleriot  with  the  addition  of  a  movable, 


296 


TYPES   OF   AEROPLANES 


101 


Fig.  47.      Diagram  of  Etrich  Bird- Wing  Monoplane 


297 


102  TYPES   OF   AEROPLANES 

central,  ash  skid  which  is  controlled  simultaneously  with  the  rudder 
by  a  pedal.  The  wheels  are  pivoted  so  that  the  machine  may  be 
steered  when  on  the  ground. 

The  body  is  a  fish-shaped  structure  of  four  wood  longitudinal 
spars,  cross  braced  by  wire  guys.  From  the  engine  bed,  which  is 
mounted  at  the  forward  end,  the  body  deepens  and  widens  in  the 
vicinity  of  the  pilot's  seat,  from  which  point  it  gradually  tapers,  still 
preserving  its  triangular  section,  until  the  tail  is  reached,  where  it 
terminates  in  a  vertical  line.  To  avoid  internal  disturbance  in  the 
air  discharge,  the  body  is  covered  forward  with  aluminum  sheeting 
and  aft  with  fabric.  The  radiator  is  an  inverted  V  suspended  above 
the  passenger's  seat,  its  height  above  the  motor  securing  effective 
thermo-siphon  circulation  in  case  the  centrifugal  pump  becomes 
deranged.  The  Etrich  machine  illustrated  is  fitted  with  a  60-horse- 
power,  four-cylinder  motor,  while  other  types  of  the  same  are  a 
120-horse-power,  three-passenger  monoplane  and -a  racing  machine 
of  60  horse-power.  Etrich  has  also  built  another  novel  type  with 
bird-form  wings  termed  the  "swallow." 

Queen=Martin  Biplane.  The  Queen-Martin  biplane,  Fig.  48, 
is  an  American  machine  and  is  a  representative  of  a  type  that  is  now 
becoming  numerous.  It  is  really  a  cross  between  a  monoplane  and 
a  biplane,  the  main  structure  being  patterned  after  the  Wright  sys- 
tem, while  the  placing  of  the  motor  and  the  arrangement  of  stabiliz- 
ing and  controlling  surfaces  are  similar  to  the  Bleriot,  being  carried 
on  the  end  of  a  long  fuselage.  The  spread  is  30  feet,  with  a  chord  of 
5  feet  1  inch,  the  planes  being  single-surfaced  and  having  the  ribs 
slipped  into  pockets  sewed  in  the  fabric.  The  planes  are  spaced 
5  feet  apart  vertically  and  the  struts  are  held  in  brazed  steel  sockets, 
double  guyed  with  nickel-plated,  flexible  cable.  The  main  beams  are 
of  ash  and  of  square  section,  with  simply  enough  rounding  of  the 
edges  to  prevent  cutting  the  fabric,  the  ribs  being  screwed  to  the  top 
of  the  forward  beam  and  to  the  under  side  of  »the  rear  one.  There  are 
three  sections  to  each  plane,  the  ribs  at  the  junction  points  being 
of  square  box  construction  with  intervening  solid  ribs  of  rectangular 
section.  Near  the  center  is  a  T-rib  of  the  Farman  type,  while  the 
outermost  ones  at  the  extremities  of  the  planes  are  of  the  usual  L 
design.  Spruce  is  used  for  the  struts,  except  in  the  center  section, 
and  also  for  the  small  ribs,  the  box  ribs  being  elm.  The  sections  are 


TYPES   OF   AEROPLANES 


103 


joined  by  lengths  of  square  steel  tubing  fitting  over  the  ends  of  the 
beams  and  bolted.     The  fuselage  is  in  two  sections  joined  by  square 


steel  sleeves,  the  aviator's  seat  being  in  the  forward  section  just  at 
the  trailing  edge  of  the  lower  plane.     Under  this  seat  is  placed  a 


299 


104  TYPES   OF   AEROPLANES 

large  supplementary  gasoline  tank,  from  which  fuel  can  be  trans- 
ferred by  the  aviator  to  the  gravity  tank  in  front  of  him.  The  avia- 
tor has  to  look  over  the  gravity  tank  as  is  the  case  in  a  monoplane. 
Lateral  control  is  by  means  of  positive  acting  ailerons  hinged  to  the 
rear  upper  beam  operated  through  a  gate  control  of  the  Burgess 
type,  as  shown  in  the  longitudinal  elevation,  Fig.  48.  Either  hand 
may  be  used  when  it  is  desired  to  rest  the  other. 

The  elevator  is  in  two  parts  and  each  half  operates  in  conjunc- 
tion with  the  ailerons  on  the  same  side,  though  in  the  proportion  of 
but  1  to  6.  The  aileron  cables  have  a  certain  amount  of  slack  to 
avoid  any  turning  movement  of  the  aeroplane,  also  to  avoid  unequal 
pressures  on  the  ailerons.  The  vertical  members  of  this  gate  con- 
trol are  universally  pivoted  to  permit  of  working  the  elevator  in 
that  capacity  alone. 

The  tail  or  rear  stabilizing  surface  is  a  perfectly  flat,  semicircular 
plane  fixed  in  place.  Hinged  to  the  rear  edge  of  this  are  the  two 
elevators  which  are  also  semicircular  in  shape.  They  are  operated 
simultaneously  by  a  fore-and-aft  motion  of  the  gate  control  through 
crossed  cables.  Both  of  the  elevators  are  double  surfaced  and  they 
are  separated  by  the  width  of  the  fuselage.  The  rudder  is  of  semi- 
circular form,  double  surfaced,  and  is  hinged  directly  to  the  rear  end 
of  the  fuselage.  It  is  operated  by  a  foot  yoke  through  cables  running 
in  guides  fastened  to  the  struts  of  the  fuselage.  The  machine  is  said 
to  be  possessed  of  such  a  high  degrees  of  inherent  stability  that  the 
ailerons  do  not  have  to  be  used  in  ordinary  weather,  and  by  stopping 
the  motor  it  immediately  assumes  its  gliding  angle  of  5  degrees.  The 
power  plant  is  a  100-horse-power  Gnome,  fourteen-cylinder  revolv- 
ing motor  driving  a  propeller  8  feet  3  inches  in  diameter  by  7  feet  G 
inches  in  pitch,  the  ignition  wiring  of  the  motor  being  so  arranged 
that  the  aviator  may  short-circuit  seven  of  the  cylinders  when  it  is 
desired  to  cut  down  the  power.  A  second  switch  cuts  out  the  second 
set  of  seven  cylinders.  The  large,  horizontal  tank  is  divided  into  two 
equal  compartments,  one  for  gasoline,  and  the  other  for  castor  oil, 
the  latter  being  fed  directly  with  the  fuel  to  a  Gnome  motor  in  the 
proportion  of  about  1  to  5.  Ash  skids  are  used  in  connection  with 
the  usual  rubber,  spring-mounted  wheels  on  the  running  gear,  a 
hickory  skid  being  placed  under  the  tail.  The  weight  with  fuel  and 
oil  is  950  pounds,  sufficient  of  the  latter  being  carried  for  a  5-hour 


300 


TYPES   OF   AEROPLANES  105 

flight.  Instead  of  being  designed  to  fly  at  a  certain  angle  of  inci- 
dence, the  Queen-Martin  biplane  depends  entirely  upon  the  camber 
of  its  surfaces  for  its  lift,  which  is  very  small,  not  exceeding  2J  inches. 

Albatross  Biplane.  As  its  name  indicates,  the  design  of  this 
machine  is  somewhat  similar  to  that  of  the  Etrich  monoplane,  in 
that  it  has  flexible  surfaces  patterned  after  a  bird's  wings,  but  the 
idea  is  carried  further  by  extending  the  same  principle  to  the  tail. 
Like  the  Queen-Martin,  it  has  a  monoplane  body  and  a  single  tractor 
screw  forward,  but  the  fuselage,  instead  of  taking  the  usual  form  of  a 
rearward-tapering  box  girder  of  lattice  construction,  is  flattened 
and  broadened  out  just  behind  the  lower  main  plane  to  form  a  sup- 
port for  the  tail  which  is  a  horizontal  triangle,  similar  to  that  of  a 
bird.  The  vertical  rudder,  in  the  shape  of  an  elongated  fin,  is  placed 
directly  above  the  center  of  the  tail,  while  the  flexible  rear  end  of 
the  latter  serves  as  an  elevator,  exactly  as  it  does  in  nature.  The 
use  of  a  flattened  fuselage  at  the  rear  with  a  rudder  above  the  tail 
and  the  elevator  at  its  extremity  was  inaugurated  by  Bleriot  in  his 
racing  machines  in  the  summer  of  1911.  It  has  proved  so  efficient 
that  it  has  since  been  adopted  by  a  number  of  the  leading  foreign 
manufacturers  and  is  a  feature  of  the  Bleriot  French  army  machines. 
In  the  Albatross,  which  is  of  German  manufacture,  the  lower  plane 
is  very  much  smaller  than  the  upper,  while  the  struts  between  them 
are  placed  diagonally,  thus  eliminating  the  use  of  the  usual  numerous 
stays  and  wire  braces.  The  ends  of  the  upper  main  plane  taper  to 
a  point  in  the  form  c^f  a  bird's  wing  and  for  several  feet  from  the  end 
they  are  flexible,  this  use  of  flexible  wing  and  tail  surfaces  doing 
away  with  all  supplementary  stabilizing  planes,  the  area  of  the  tail 
being  unusually  large,  while  its  supporting  effort,  instead  of  being 
utilized  merely  at  the  end  of  the  lever,  is  extended  to  a  point  just 
back  of  the  lower  main  plane.  More  than  twenty  of  the  Albatross 
biplanes  have  been  made  for  the  German  army. 

Breguet  Biplane.  Breguet  was  one  of  the  first  French  construct- 
ors to  adopt  the  arrangement  originated  by  the  Wrights  of  running 
a  large  diameter  propeller  at  low  speed,  and  he  was  also  a  pioneer 
in  the  introduction  of  the  biplane  with  a  monoplane  type  of  body 
and  placing  of  the  power  plant.  The  unusually  high  efficiency  gained 
is  evidenced  from  the  fact  that  with  an  ordinary  two-passenger 
biplane  he  has  carried  six  persons  of  a  total  weight  of  924  pounds, 


301 


106  TYPES   OF   AEROPLANES 

which  is  very  close  to  that  of  the  weight  of  the  machine  itself — 1,045 
pounds — while  his  racing  machines  have  also  proved  unusually 
speedy.  The  span  is  43.3  feet,  but  the  lower  plane  is  only  32.5  feet 
wide,  with  a  chord  of  5.6  feet.  A  five-cylinder,  semi-radial  R.  E.  P. 
motor  of  50  to  60  horse-power  drives  a  two-bladed  propeller  9.5  feet 
in  diameter  and  of  variable  pitch  through  reduction  gearing.  The 
entire  fuselage  is  enclosed  with  fabric,  and  the  combined  rudder  and 
elevating  plane  in  the  form  of  a  cross  are  hung  from  its  after  end  on 
a  universal  joint.  Control  is  by  means  of  a  wheel  placed  on  a  column, 
as  in  the  Curtiss,  revolving  the  wheel  causing  the  rudder  to  turn, 
while  pushing  or  pulling  on  it  moves  the  column  back  and  forth  and 
actuates  the  elevator.  Pushing  the  wheel  from  side  to  side  flexes 
the  wings,  thus  centering  the  control  on  a  single  lever.  With  the 
motor  in  question,  its  speed  is  53  miles  per  hour,  but  a  special  racing 
type  with  only  280  square  feet  of  supporting  surface  and  a  higher- 
powered  motor  is  also  made. 

Tubavion  Monoplane.  Very  radical  departures  from  accepted 
standards  of  monoplane  construction  are  found  in  this  machine.  A 
long  steel  tube  forms  the  backbone  and  replaces  the  usual  mono- 
plane body,  while  converging,  upward-curving  skids  are  attached 
to  this  tube  at  the  front  and  rear,  thus  making  what  is  practically  an 
"underslung"  type,  the  motor  being  placed  forward  under  a  bonnet 
closed  in  front  by  the  radiator,  as  on  an  automobile.  The  propeller 
is  mounted  on  the  main  steel  tube  forming  the  backbone,  just  back 
of  the  main  plane,  and  is  chain  driven  from  an  extension  of  the 
engine  shaft  which  runs  back  beneath  the  pilot's  seat,  thus  giving 
an  arrangement  of  the  motor  in  front  and  the  propeller  at  the  rear. 
In  fact,  the  power  plant  has  been  brought  right  up  to  date  by  pro- 
viding the  motor  with  a  self-starter,  so  that  it  may  be  re-started  in 
the  air  in  case  of  accidental  stoppage.  The  pilot  sits  directly  behind 
the  motor.  Several  machines  built  on  this  general  principle,  i.  e., 
monoplanes  with  a  small  underslung  car  in  place  of  the  usual  mono- 
plane body,  made  their  appearance  at  the  Paris  aeroplane  show  late 
in  the  winter  of  1911. 

Morane  Monoplane.  While  this  machine  is  in  general  based 
upon  Bleriot  lines,  Morane  having  been  an  associate  of  Bleriot's  for 
some  time,  it  is  noticeable  for  the  entire  suppression  of  the  dihedral 
angle  between  the  two  wings  and  their  flatness  on  the  under  side, 


302 


TYPES   OF   AEROPLANES  107 

this  having  been  planned  to  increase  the  speed.  The  shape  of  the 
ends  of  the  wings  has  also  been  radically  altered  and  their  point  of 
maximum  camber  placed  very  close  to  the  leading  edge.  The  mast 
carrying  the  upper  wing  stays  is  pyramidal  and  is  so  arranged  that 
the  support  at  the  front  is  more  at  right  angles  to  the  wings  and  so 
better  protects  the  spars  from  over  stress.  The  rudder  is  divided 
into  two  sections  by  the  stabilizing  tail,  just  forward  of  which  is  a 
light  double  skid.  The  pilot  sits  behind  a  long  bonnet  enclosing  the 
tanks  and-  extending  over  the  engine,  in  the  type  employed  in  the 
long-distance  races  in  the  summer  of  1911,  but  at  the  Paris  salon  in 
December  of  the  same  year,  Morane  exhibited  a  strikingly  novel 
machine  of  all  steel  construction.  The  body  is  made  of  pressed  steel 
in  torpedo  shape,  i.  e.,  ovoid  forward  and  tapering  to  a  sharp  point 
aft  with  a  perfectly  smooth  finish  outside,  and  as  bracing  is  done  on 
the  interior  this  cuts  the  head  resistance  to  the  minimum.  The 
Gnome  revolving  motor  is  completely  enclosed  with  a  comparatively 
small  number  of  openings  for  cooling  it,  the  propeller  being  the  only 
part  of  the  power  plant  that  is  visible  from  the  outside.  The  use  of 
steel  tubing  for  the  beams  and  ribs  of  the  wings  also  does  away  with 
practically  all  braces  and  guys,  so  that  the  machine  should  prove 
exceptionally  fast,  even  as  compared  with  its  immediate  predecessor, 
which  showed  an  average  of  70  miles  an  hour  on  a  closed  circuit  with 
a  50-horse-power  motor.  The  chief  dimensions  are:  Span  31  feet 
6  inches;  length  22  feet  6  inches;  supporting  area  188  square  feet,  of 
which  151  square  feet  are  in  the  wings  and  the  remainder  in  the 
stabilizing  tail.  Some  idea  of  the  care  that  has  been  taken  to  reduce 
weight  is  evident  from  the  fact  that  the  complete  machine  empty 
weighs  but  440  pounds,  and  this  has  not  been  attained  at  the  sacrifice 
of  strength,  as  the  machine  is  very  solid.  Among  the  speed  per- 
formances of  the  Morane  are  the  covering  of  210  miles  in  2:12,  or  at 
the  rate  of  90  miles  an  hour  with  a  20-mile  favoring  wind;  500  miles 
in  6:55,  or  72.28  miles  for  the  entire  distance,  and  the  winning  of  the 
Paris-Madrid  race,  the  start  of  which  was  marked  by  the  killing  of 
two  aviators  and  two  French  officials  of  prominence.  In  this  race 
the  Morane  driven  by  Vedrines  was  the  only  aeroplane  to  finish, 
capturing  the  prize  of  $20,000. 

Deperdussin  Monoplane.     While  apparently  a  small  machine, 
the  Deperdussin  has  unusual  carrying  capacity  and  high  speed  with 


303 


108  TYPES   OF   AEROPLANES 

heavy  loads,  holding  all  world's  records  up  to  the  end  of  1911  for  4 
and  5  passengers  for  distances  up  to  30  miles.  Two  of  these  mono- 
planes were  brought  to  this  country  in  the  summer  of  1911  and  have 
made  an  excellent  showing  at  various  aviation  meets.  It  is  said  to 
be  one  of  the  easiest  machines  for  the  beginner  in  which  to  master 
the  difficult  art  of  flying,  and  for  this  reason  they  have  been  employed 
to  a  great  extent  by  schools  on  the  other  side.  The  wings  are  similar' 
in  shape  to  those  of  the  Antoinette  and,  in  fact,  the  entire  machine 
resembles  the  latter  to  some  extent.  In  the  regular  passenger  and 
school  machines,  the  wings  are  set  at  a  slight  dihedral  angle  and 
there  is  a  perfectly  flat  triangular  tail  plane;  but  in  the  racing  machines 
the  planes  are  flat  and  the  tail  is  of  the  lifting  type.  As  there  is  every 
reason  to  believe  that  the  non-lifting  tail  is  the  more  efficient  for  a 
machine  of  this  kind,  the  precise  reason  for  the  employment  of  a 
lifting  tail  is  rather  obscure.  The  elevator  is  hinged  to  the  rear  of  the 
tail  plane,  while  forward  of  the  rudder  extends  a  small  stabilizing 
fin.  The  control  is  one  of  the  best  points  of  the  machine,  giving 
the  greatest  possible  amount  of  freedom  to  the  pilot.  Instead  of  the 
usual  arrangement  of  a  vertical  lever  between  the  pilot's  knees,  the 
Deperdussin  has  two  side  levers  connected  by  a  pinned  crosspiece 
on  which  is  mounted  a  hand  wheel.  The  rotation  of  this  wheel  cor- 
rects the  lateral  balance,  while  a  to-and-fro  movement  controls  the 
elevator,  steering  being  effected  by  a  foot  lever  in  the  manner  com- 
mon to  French  monoplanes.  The  cables  from  the  warping  control 
are  carried  down  to  a  T-shaped  lever  mounted  on  the  rear  cross- 
member  of  the  chassis  and,  after  passing  over  pulleys  on  the  skids, 
branch  out  into  two  wires  each  and  proceed  to  two  points  on  the 
spar  of  each  wing.  By  rotating  the  wheel  to  the  right,  therefore, 
the  whole  of  the  rear  spar  of  the  left  wing  is  pulled  down,  while  the 
similar  spar  on  the  right  wing  rises  a  corresponding  distance,  and 
vice  versa.  Very  little'  wire  bracing  is  used  on  the  landing  chassis, 
rigidity  being  given  to  the  structure  by  two  wood  diagonal  struts 
in  compression,  the  forward  portion  of  the  skids  being  an  extension 
of  these  struts,  and  is  connected  to  the  skid  proper  by  a  thin  band 
of  steel  to  prevent  the  upturned  front  part  of  the  skid  from  letting 
the  machine  down  too  heavily  in  the  event  of  a  sudden  landing. 
A  peculiar  feature  noticeable  on  the  racing  type  is  that  the  big  tractor 
screw  comes  below  the  skids  when  in  the  vertical  position,  so  that  it  is 


304 


TYPES   OF  AEROPLANES  109 

almost  certain  to  be  smashed  in  the  event  of  a  rough  landing.  Two 
Deperdussin  monoplanes  shared  the  honors  with  the  Nieuport  by 
being  the  only  three  monoplanes  to  meet  the  severe  conditions 
imposed  by  the  French  military  authorities  in  the  1911  competition. 

Valkyrie  Monoplane.  The  Valkyrie  is  one  of  the  few  English 
machines  of  this  type.  It  is  a  peculiar  combination  of  mono- 
plane and  biplane  features,  resembling  in  one  respect  the  Voisin 
canard  type,  by  having  the  elevator  and  a  pair  of  stabilizing  fins 
way  forward  of  the  main  planes,  and  in  another,  the  original  Wright 
machine,  in  that  the  elevator  is  forward  and  the  vertical  rudder  aft 
of  the  main  planes,  though  structurally  it  does  not  resemble  either 
of  these  types  particularly.  The  main  planes  are  in  three  sections, 
the  center  one  being  given  a  shorter  chord  than  the  other  to  allow 
room  for  the  propeller,  while  the  two  outer  sections  are  set  at  a 
pronounced  dihedral  angle.  There  is  also  a  longitudinal  dihedral 
angle  between  the  main  planes  and  the  forward  fixed  plane,  which 
is  placed  above  the  elevator  and  is  given  an  angle  of  incidence  of 
9  degrees,  while  that  of  the  wings  is  13  degrees.  The  front  fixed  plane 
is  placed  11  feet  9  inches  forward  of  the  main  planes  and  its  angle 
may  be  varied  to  compensate  for  changes  in  the  loading.  The  ele- 
vator, which  is  below  and  at  the  rear  of  the  forward  fixed  plane,  is 
characterized  by  a  slightly  upturned  trailing  edge.  All  planes  are  of 
the  single  surface  type  and  of  Farman  construction.  Lateral  stability 
is  secured  by  the  use  of  flaps  at  the  extremities  of  the  wings,  but 
warping  can  be  usec^.  Twin  vertical  rudders  some  distance  apart 
and  placed  three  feet  back  of  the  main  planes  are  employed.  It  has 
been  found  necessary  to  fit  "blinkers,"  or  small  vertical  fins  similar 
to  those  used  between  the  forward  braces  on  the  Wright,  as  without 
them,  when,  making  a  short  turn,  the  machine  was  likely  to  turn 
completely  about  its  radius  of  gyration  and  come  to  the  ground  in 
a  heap.  The  running  gear  is  of  the  Farman  type. 

Hanriot  Monoplane.  The  Hanriot  is  another  French  mono- 
plane that  has  made  such  a  favorable  name  for  itself  abroad 
that  plans  have  been  made  to  produce  it  in  this  country,  the  mono- 
plane being  a  type  that  has  not  been  particularly  developed  in 
America,  unfortunately.  There  are  many  points  of  distinct  origi- 
nality in  the  Hanriot  design  and  construction.  Chief  among  these  is 
the  wood,  boat-shaped  hull,  supported  on  three  A-frames  from  the 


305 


110  TYPES   OF   AEROPLANES 

chassis,  which  makes  a  remarkably  simple  and  strong  construction, 
while  the  boat-like  body  dispenses  with  the  usual  great  amount  of 
wire  necessary  to  brace  a  girder  or  box  frame.  This  body  is  almost 
a  replica  of  the  usual  racing  scull,  being  entirely  decked  in  except 
for  a  small  cockpit  to  accommodate  the  aviator  and  the  controls, 
this  deck  being  made  strong  enough  for  the  aviator  to  stand  upon. 
Three  steel  ribbons  form  a  support  for  the  body  on  the  A-type  chassis 
frame,  and  steel  tapes  are  also  employed  for  lashing  the  main  spars 
of  the  wings  to  the  body.  These  spars  are  laminated,  a  form  of 
construction  that  overcomes  the  usual  tendency  of  the  monoplane 
spars  to  buckle.  The  E.  N.  V.  eight-cylinder,  V-type,  40-horse-power 
motor  is  carried  well  forward  of  the  main  planes,  where  it  is  mounted 
on  the  bow  of  the  boat  body,  and  is  also  partly  supported  by  the 
struts  of  the  A-framing  of  the  chassis.  An  unusually  large  rear  sta- 
bilizing plane  is  employed,  measuring  9  feet  3  inches  in  depth  by  8 
feet  in  widthj  in  the  form  of  a  triangle.  Two  elevating  planes  are 
hinged  to  the  rear  edge  of  this  fixed  plane,  with  a  space  for  the  rudder 
between  them.  The  span  of  the  main  planes  is  30  feet  and  the  chord 
7  feet  and  they  are  set  at  a  dihedral  angle  of  1  in  25 ;  their  total  area 
is  184  square  feet.  This  fixed  tail  plane  is  quite  flat  and  consists  of  a 
single  surface  stretched  tightly  by  the  aid  of  two  transverse  spars. 
Its  rear  portion  is  deflected  a  little  below  the  line  of  the  leading 
edge,  to  which  it  has  a  relative  though  small  angle  of  inclination. 

Curtiss  Racing  Machine.  In  developing  a  racing  machine,  the 
Wright  Brothers  have  proceeded  along  exactly  the  same  lines  as  in 
their  regular  type  of  machine,  high  speed  being  obtained  by  cutting 
down  the  supporting  surface  and  increasing  the  power.  The  Curtiss 
racing  machine,  however,  is  a  special  type,  in  that  it  is  not  exactly 
either  a  biplane  or  a  monoplane.  As  will  be  apparent  from  the 
photograph,  Fig.  49,  it  is  a  cross  between  the  two  and  is  accordingly 
in  a  class  of  its  own.  So  far  as  its  main  supporting  surface  is  con- 
cerned, it  is  a  monoplane;  but,  placed  centrally  above  this  main 
plane,  is  another  but  very  much  smaller  plane  which  resembles  a 
canopy  more  than  anything  else.  This  small  upper  surface  is  not 
employed  merely  for  the  purpose  of  obtaining  additional  supporting 
area,  but  simply  to  take  advantage  of  the  support  afforded  by  the 
tubular,  vertical  struts  for  the  attachment  of  the  guy  wires.  The 
elevating  plane  is  placed  in  front  but  quite  close  to  the  main  plane, 


306 


TYPES   OF   AEROPLANES  111 

and  it  is  a  single  surface  instead  of  the  usual  biplane  cell  employed 
on  the  regular  Curtiss  machine.  There  is  also  a  rear  plane,  but 
instead  of  arranging  this  to  move,  its  rear  edge  is  made  flexible  and 
it  also  acts  as  an  elevator,  thus  providing  the  machine  with  an 
elevating  rudder  both  front  and  rear.  The  running  gear,  as  will  be 
apparent,  is  closely  modeled  after  the  customary  Curtiss  standards, 
but  the  framework,  instead  of  being  of  bamboo  or  light  wood,  is 
largely  composed  of  steel  tubing. 

The  usual  balanced  vertical  rudder  is  placed  at  the  rear  and 
small  vertical  keels  are  used  forward  to  offset  the  effect  of  side  winds 
on  the  rudder.  The  wings  are  rigid  and  are  fitted  with  hinged 
ailerons  as  in  the  Far  man  type.  These  ailerons  have  a  spread  of 
6  feet  2  inches  by  a  depth  of  20  inches  and  are  operated  by  means  of 
cables  attached  to  a  shoulder  brace  as  in  the  regular  Curtiss  machine. 


Fig.  49.      Curtiss^  Racing  Machine.      This  is  Practically  a  Monoplane 

The  main  planes  have  a  spread  of  29  feet  and  a  depth  of  4  feet  6 
inches,  giving  an  area  of  120.5  square  feet.  The  front  elevator 
measures  6  feet  2  inches  by  2  feet  8  inches,  while  the  rear  elevator 
has  a  spread  of  8  feet  2  inches  and  a  depth  of  2  feet  10  inches,  the 
rear  edge,  which  can  be  flexed,  having  a  depth  of  20  inches.  This 
makes  the  total  supporting  area  of  the  machine  1GO  square  feet, 
exclusive  of  the  small  upper  plane. 

The  mottor  is  an  eight-cylinder,  four-cycle  V-type,  water-  instead 
of  air-cooled,  the  valves  being  placed  in  the  heads  of  the  cylinders. 
The  cylinder  dimensions  are,  bore  4  inches,  stroke  4|  inches.  It 
weighs  250  pounds  all  told  and  develops  70  horse-power.  Lubrication 
is  by  means  of  a  rotating  vein  oil  pump,  the  supply  being  carried  in 


307 


112  TYPES   OF   AEROPLANES 

a  wedge-shaped  tank  below  the  motor.  The  radiator  is  placed  forward 
of  the  motor  and  just  behind  the  aviator.  Mounting  is  on  three 
12-inch  wheels  shod  with  heavy  pneumatic  tires,  while  instead  of  the 
spoon  brake  employed  on  the  front  wheel  of  the  regular  Curtiss 
machine,  two  sprags  are  attached  to  the  main  axle.  It  was  found 
that  the  front  wheel  bore  such  a  small  part  of  the  weight  that 
a  brake  was  not  effective.  These  sprags  are  brought  into  opera- 
tion by  an  extreme  forward  movement  of  the  vertical  steering  wheel, 
the  remainder  of  the  control  consisting  of  a  foot-operated  throttle  for 
the  motor,  and  the  working  of  the  ailerons  by  the  shoulder  braces, 
the  turning  of  the  steering  wheel  governing  the  vertical  rudder.  The 
propeller  is  of  laminated  spruce,  8  feet  in  diameter  by  a  6-foot  pitch, 
and  is  attached  directly  to  the  crank  shaft  of  the  motor. 

The  front  control  is  placed  8  feet  forward  of  the  main  plane, 
while  the  rear  control  is  14  feet  back  of  it,  giving  the  machine  a1 
total  depth  of  26  feet  overall.  Very  little  wood  is  used  in  the  con- 
struction of  the  framework,  thin  steel  tubing  predominating,  while 
the  surfaces  of  the  planes  are  composed  of  the  thinnest  racing  yacht 
sail  cloth.  This  is  the  Curtiss  machine  that  was  designed  and  built 
to  compete  in  the  Gordon-Bennett  contest  at  Belmont  Park  in  the 
fall  of  1910,  but  which  was  finally  not  entered. 

Multiplanes.  It  will  be  noted  that  neither  in  the  article  on 
"Standard  Types,"  nor  in  the  present  one,  has  any  mention  been  made 
of  machines  with  more  than  two  independent  surfaces.  In  fact,  all 
of  the  machines  that  have  been  successfully  flown  to  any  great  extent 
thus  far,  have  either  been  biplanes  or  monoplanes.  One  reason  for 
not  attempting  to  use  more  than  two  planes  is  to  be  found  in  the 
greater  complication  involved  in  the  construction,  as  well  as  the 
introduction  of  a  new  factor  brought  about  by  the  increase  in  the 
height  of  the  machine — that  of  vertical  stability.  With  good  control 
of  the  lateral  stability  by  warping  or  ailerons,  and  of  longitudinal 
stability  by  means  of  the  tail  and  elevating  rudder,  the  aviator  can 
safely  disregard  this  third  factor.  Unless  something  happens  to  the 
machine  it  is  in  no  danger  of  assuming  an  angle  of  inclination  to  the 
horizontal  that  would  tend  to  rob  it  of  supporting  power  to  an  extent 
that  would  make  a  fall  imminent  through  the  aeroplane  "standing  on 
its  head,"  or  the  reverse.  With  the  towering  structure  represented 
by  three  or  more  superimposed  planes,  it  appears  as  if  a  sudden  gust 


308 


TYPES   OF   AEROPLANES 


113 


of  wind — a  sharp  puff  that  happened  to  strike  the  upper  planes  and 
not  the  lower  ones,  as  is  quite  possible,  or  a  strong  slant  of  wind 
that  exerted  considerably  more  pressure  upon  the  upper  part  of  the 
machine  than  it  did  on  the  lower — would  be  quite  likely  to  cause 
this  result.  It  will  be  recalled  that  the  Wright  Brothers  give  it  as 
their  opinion  that  no  advantage  is  to  be  gained  by  increasing  the 
number  of  planes  above  two. 

Roe.  However,  so  many  obvious  theories  that  apparently  can 
not  fail  to  hold  good  in  practice  have  been  upset  by  the  results 
obtained  in  flights  with  various  types  of  machines,  that  it  is  difficult 
to  put  any  of  them  down  as  entirely  untenable  until  this  has  been 


Fig.  50.     Roe  Multiplane 

demonstrated  by  experiment.  Unfortunately,  most  of  the  experi- 
ments with  multiplanes  so  far  have  not  resulted  successfully.  Some, 
on  the  other  hand,  have  given  considerable  promise  but  have  been 
carried  out  only  on  a  small  scale.  The  first  public  appearance  of  a 
triplane  was  at  the  Harvard  Aviation  Meet,  in  September,  1910. 
The  machine  was  designed  and  built  by  A.  V.  Roe,  an  Englishman, 
who  also  attempted  to  fly  the  machine.  As  will  be  apparent  from  the 
photograph  of  this  machine,  Fig.  50,  it  is  practically  a  Farman  biplane, 
with  the  addition  of  a  third  plane  of  smaller  dimensions  placed  below 
the  other  two.  The  tail  is  likewise  a  triplane.  Control  of  lateral 
stability  is  attained  in  the  same  manner  as  in  the  Farman,  i.  e., 


309 


114 


TYPES   OF   AEROPLANES 


by  ailerons  or  wing  tips,  but  these  are  attached  to  the  rear  surfaces 
of  the  middle  plane  instead  of  to  the  upper  plane  as  in  the  French 
machine.  The  motor  is  mounted  at  the  forward  edge  of  this  central 
plane  with  the  direct-connected  propeller  placed  in  front,  while  the 
aviator's  seat  is  placed  in  the  framework  about  on  a  level  with  the 
third  or  lowest  plane.  The  construction  of  this  frame  is  somewhat 
similar  to  that  of  the  Bleriot.  The  machine  is  mounted  on  two  pairs 
of  pneumatic-tired  wheels  attached  to  long  skids,  as  in  the  Farman, 
while  a  third  small  skid  is  placed  under  the  elevating  rudder.  On 
the  only  occasion  on  which  the  Roe  triplane  was  used  at  the  Harvard 
Meet,  it  made  a  short  flight,  Fig.  51,  and  then  dove  to  the  ground, 


Fig.  51.     Roe  Multiplane  in  Flight 

wrecking  itself.  As  many  successful  machines  have  performed  in  a 
similar  manner  in  the  hands  of  unskilled  aviators,  this  does  not 
necessarily  imply  a  fault  in  the  design,  nor  for  that  matter  a  lack 
of  skill,  as  something  may  have  gone  wrong  with  the  control. 

Roe  has  been  a  persistent  experimenter  with  the  triplane  and 
worked  at  the  problem  for  a  long  while,  developing  his  first  machine 
in  which  he  succeeded  in  getting  off  the  ground.  This  was  practically 
a  Langley  aerodrome  in  triplicate  and  not  the  machine  used  at 
Boston.  The  three  planes  were  of  the  same  area  and  were  attached 
to  three  similar  but  smaller  planes,  forming  the  tail  by  means  of  a 
triangular  frame.  It  was  mounted  on  two  wheels  forward  under  the 


310 


TYPES   OF   AEROPLANES  115 

main  planes  and  a  skid  at  the  rear,  the  aviator  sitting  in  the  body 
or  enclosed  frame  about  midway  between  the  main  planes  and  the 
tail.  The  forward  or  main  supporting  surfaces  measured  20  feet  in 
spread  by  a  depth  of  3  feet  7  inches,  while  the  rear  planes  were  of 
the  same  depth  with  exactly  half  the  spread,  or  10  feet,  giving  a 
total  area  of  320  square  feet.  The  motor  of  but  10  horse-power  was 
mounted  originally  at  the  forward  end  of  the  framing  and  carried  a 
three-bladed  propeller  directly  on  its  crank  shaft.  With  this  motor 
the  total  weight  of  the  machine  itself  was  but  200  pounds,  or  with 
the  aviator,  about  350  pounds,  thus  lifting  35  pounds  per  horse- 
power. Subsequently,  a  20-horse-power  motor  was  installed  and  the 
weight  of  the  machine  considerably  increased.  The  body  is  con- 
structed of  deal  (spruce)  and  is  covered  with  oiled  paper  backed  with 
muslin.  Instead  of  the  usual  elevating  rudder,  the  machine  is  caused 
to  ascend  or  descend  by  altering  the  angle  of  incidence  of  the  main 
planes  themselves,  all  three  being  pivoted  for  this  purpose.  The 
transverse  control  consisted  of  warping  the  rear  edges  of  the  main 
planes  in  the  usual  manner  and  at  the  same  time  employing  the 
vertical  rudder  at  the  rear.  With  this  machine,  a  number  of  short 
flights  in  a  straight  line  were  made,  the  most  striking  feature  being 
the  low  power  necessary. 

Sellers.  From  similar  experiments  made  in  this  country,  the 
possibility  of  greatly  increasing  the  efficiency  as  represented  by  the 
present-day  standard  appears  to  be  the  chief  promise  held  out  by  the 
multiplane.  M.  B.  Sellers,  a  Kentuckian,  has  made  extended  experi- 
ments in  this  direction  with  a  quadruplane  and  has  made  a  number 
of  flights,  using  a  Bates  two-cylinder  opposed  motor  rated  at  but 
10  horse-power.  The  four  planes  are  not  placed  directly  above  one 
another,  but  are  joined  in  the  form  of  a  parallelogram  with  a  forward 
inclination  from  the  vertical  in  the  direction  of  the  machine's  flight, 
thus  bringing  each  surface  slightly  in  advance  of  the  one  below. 

Zerber.     Another  type,  the  Zerber,  is  shown  in  Fig.  52. 

Paulhan  Triplane.  Paulhan  has  brought  out  a  triplane  of  the 
same  construction  as  the  box-girder  type  already  described,  but 
trials  made  with  it  during  the  summer  of  1911  were  not  successful. 

Maxim.  A  machine  that  probably  conforms  less  to  the 
standards  already  set  forth  than  any  other  is  the  new  Maxim 
aeroplane,  about  the  construction  of  which  considerable  secrecy  has 


311 


116 


TYPES   OF   AEROPLANES 


been  maintained.  It  is,  in  fact,  the  Maxim  flying  machine  of  almost 
twenty  years  ago  brought  down  to  date,  every  part  of  it,  even 
including  the  motor  and  propellers,  being  made  by  the  inventor 
himself,  in  accordance  with  his  own  theories.  His  first  care  was  to 
reduce  the  proportions  of  the  machine  as  compared  with  the  gigantic 
apparatus  built  at  a  cost  of  §100.000  in  1S94.  The  spread  of  the 
new  aeroplane  is  but  44  feet — large  in  comparison  with  most  standard 


9 


Tut.  52.     Zerber  Multiplane 

machines,  but  not  when  compared  with  the  spread  of  over  100  feet 
of  the  original  Maxim.  Like  its  prototype,  the  new  aeroplane  is  of 
the  multiplane  type  and  is,  in  effect,  made  up  of  six  aeroplanes,  each 
being  6  feet  6  inches  in  depth,  giving  it  an  aspect  ratio  of  6.77.  The 
planes  are  noticeably  thin  and  consist  of  waterproof  silk,  very  tightly 
laced  on.  From  the  central  plane  spring  out  two  superposed  wings, 
raised  well  above  it,  and  so  curved  as  to  produce  inherent  lateral 
stability  to  a  very  high  degree. 

There  are  balanced  rudders  fore  and  aft  and  a  horizontal  steer- 
ing rudder,  the  Maxim  patent  device  for  altering  the  pitch  of  the 


312 


TYPES  OF  AEROPLANES  117 

planes  when  in  flight  being  utilized.  This  differs  from  the  Wright 
warping  device  in  that  the  wings  are  moved  in  one  direction  by  a 
lever  worked  by  hand,  while  a  spring  controls  them  in  the  reverse 
direction. 

The  engine  is  mounted  between  the  planes  and  behind  the  pilot, 
who  sits  in  a  low,  metal-covered  compartment,  with  the  steering  and 
control  levers  directly  in  front  of  him.  One  of  the  most  novel  features 
of  the  machine  is  its  power  plant  and  drive.  On  the  engine  shaft  is 
one  small  propeller,  mounted  at  the  rear  of  the  planes.  This  screw 
turns  at  the  same  rate  as  the  engine  shaft  and  also  serves  as  a  fly- 
wheel. In  addition,  there  are  two  large  propellers,  11  feet  in  diam- 
eter, mounted  higher  up  between  the  planes  and  driven  by  steel 
cables  kept  taut  by  idler  pulleys.  The  small  screw  and  one  of  the 
large  ones  rotate  in  the  same  direction,  while  the  other  large  one 
turns  in  the  opposite  direction.  This  screw  is  also  given  a  finer 
pitch  and  a  higher  velocity  than  its  companion  and  in  this  way  its 
gyroscopic  action  balances  the  joint  gyroscopic  action  of  the  other 
two  propellers,  rotating  in  the  reverse  direction. 

The  motor  is  a  four-cylinder,  vertical,  water-cooled  type  of  60 
horse-power,  built  throughout  of  a  special  grade  of  Vickers  steel, 
making  it  amply  strong  but  very  light.  Special  attention  has  been 
paid  to  the  valve  and  carbureter  design  and  a  greater  degree  of  relia- 
bility is  claimed  for  the  engine  than  those  usually  employed  in  avia- 
tion. An  ingenious  force-feed  system  of  lubrication  is  employed 
which  carries  oil  to  every  working  part  of  the  motor  in  a  very  effec- 
tive manner.  The  radiator  is  mounted  under  the  upper  plane  in  a 
manner  somewhat  similar  to  that  employed  on  Santos-Dumont's 
Demoiselle. 

The  whole  machine  is  mounted  on  wheels  and  shock  absorbers. 
There  is  a  noticeable  absence  of  the  complication  of  stays,  guy  wires, 
and  framework  common  to  the  usual  biplane  construction,  and  which 
causes  so  much  head  resistance.  The  grouping  of  the  various  mem- 
bers has  been  skillfully  carried  out,  those  parts  creating  the  greatest 
resistance  being  set  as  far  as  possible  in  line  behind  one  another. 
Like  its  predecessor,  it  has  also  been  experimented  with  in  a  captive 
state,  but  instead  of  the  tracks  on  which  the  first  Maxim  machine 
ran,  an  apparatus  similar  to  that  designed  by  Captain  Ferber  is 
employed.  This  consists  of  a  mast  with  a  huge  revolving  arm,  per- 


313 


118  TYPES   OF   AEROPLANES 

mitting  the  aeroplane  to  fly  in  a  circle  round  its  support.  When  so 
many  other  new  machines  are  experimented  with  in  free  flight  by- 
aviators  of  litt'e  or  no  experience,  the  Maxim  method  scarcely  appears 
necessary,  though  it  at  least  has  the  virtue  of  greater  safety. 

Steel  Tube  Construction.  That  there  is  likewise  ample  room 
for  improvement  in  constructional  details  will  be  obvious  upon  a 
consideration  of  the  methods  and  materials  employed  in  building 
the  standard  types  of  aeroplanes  already  described.  Crudity  was  to 
be  looked  for  at  first — many  successful  experimenters  had  neither 
the  means  nor  the  facilities  to  employ  special  materials  or  construc- 
tion. They  were  in  much  the  same  position  as  early  experimenters 


Fig.  53.     Fairchild  Monoplane  with  Frame  of  Steel-Tube  Construction 

in  the  automobile  field.  But  now  that  so  much  has  been  done  in  the 
development  of  steels  and  light  alloys  of  tremendous  strength  for 
automobile  construction,  there  appears  to  be  no  reason  why  they 
should  not  be  taken  advantage  of  to  replace  the  more  cumbrous  and 
none  too  safe  wood  or  bamboo  framing.  Two  instances  of  this 
are  shown  in  Figs.  53,  54,  and  55.  Many  of  the  new  machines  pro- 
duced during  1911  employ  steel  tubing  to  a  greater  or  less  extent. 

Fairchild  Monoplane.  The  Fairchild  (American)  is  one  of  the 
few  types  of  monoplanes  extant,  employing  two  propellers.  It  is, 
in  fact,  a  model  of  mechanical  construction,  and  if  its  flying  capabili- 


314 


TYPES   OF   AEROPLANES 


119 


ties  are  in  any  way  commensurate  with  the  intelligence  and  resource- 
fulness displayed  in  the  working  'out  of  its  design,  it  would  seem  to 
presage  the  advent  of  the  eminently  successful  American  monoplane. 


Fig.  '54. 


Henri  Farman  in  His  New  Monoplane. 
Tube  Construction 


The  Frame  is  of  Steel- 


The  frame  is  of  graduated  steel  tubing,  lightness  with  maximum 
strength  having  been  obtained  through  the  use  of  different  diameters 
and  thickness  of  tubes,  the  necessary  strength  of  each  part  having 
been  carefully  calculated  in  detail.  Wherever  special  strength  is 
required,  the  tubes  are  forced  over  elm  poles.  In  the  trussing  of 
the  frame,  steel  tape  and  cable  are  employed  in  place  of  the  usual 


Fig.  55.      Front  View  of  Farman  Monoplane 


piano  wire,  which,  though  very  strong,  is  an  uncertain  factor  and 
likely  to  give  way  unexpectedly. 

The  wings  are  of  the  usual  monoplane  type  and  are  built  up  of  14 
double,  ribs  over  transverse  1-inch  steel  tubes.     They  have  flexible 


315 


120  TYPES   OF  AEROPLANES 

curved  tips  which  are  balanced  for  a  certain  lifting  effect,  but  which 
can  not  be  controlled  by  the  aviator.  The  tail  is  similar  to  the  flat 
type  of  the  Antoinette  and  is  employed  solely  as  a  stabilizer,  its 
lifting  capacity  alone  being  equal  to  sustaining  itself  and  the 
weight  of  the  framework  attaching  it  to  the  body.  Vertical  and 
horizontal  changes  of  direction  are  obtained  through  rear  rudders  of 
the  Antoinette  type,  except  that  a  further  vertical  rudder  in  front 
of  the  hinge,  in  prolongation  of  the  rear  one,  occupies  the  position 
of  the  French  machine's  fixed,  vertical  fin.  Efficient  lateral  control 
is  expected  from  a  novel  and  very  radical  device,  the  construction  of 
which  the  builder  did  not  wish  to  reveal  at  the  time. 

Like  the  Bleriot  XII,  the  Demoiselle,  and  the  Grade,  the  Fair- 
child  monoplane  has  its  center  of  gravity  comparatively  low,  but 
unlike  these  machines,  the  aviator  sits  above.  It  is  anticipated  that 
any  tendency  toward  oscillation  produced  by  thus  placing  the  center 
of  gravity  low  will  be  overcome  by  a  large,  vertical  fin  placed  directly 
over  the  center  of  the  machine  between  the  main  planes,  as  well  as 
the  fact  that  two  propellers  are  employed  for  propulsion,  or  rather 
traction,  as  both  will  draw  the  machine,  and  both  are  designed  to 
revolve  in  the  same  direction — contrary  to  all  precedent  in  this  field. 
Fairchild  holds  that  if  the  gyroscopic  effect  of  a  single  propeller 
can  be  deemed  negligible  in  the  monoplane,  that  of  two  is  even  more 
so.  These  propellers  have  a  7-foot  diameter  and  a  6-foot  pitch. 

The  motor  is  a  six-cylinder,  two-cycle  Emerson  rated  at  100 
to  125  horse-power.  It  is  of  a  special  four-port  type  and  is  said  to 
show  great  efficiency,  having  developed  in  excess  of  134  horse-power 
on  a  brake  test.  It  is  mounted  at  the  lowest  point  of  the  main  frame 
below  the  center  of  the  wings  and  just  above  the  landing  chassis 
which  is  exceptionally  wide  and  strong.  A  pair  of  pneumatic-tired 
wheels  support  the  fore  part  of  the  machine  when  on  the  ground,  the 
supporting  columns,  which  are  double,  forming  part  of  the  frame; 
the  forks  carrying  the  wheels  are  hinged  to  the  lower  ends  of  the 
tubes  and  the  wheel  hubs  are  stayed  independently  to  loose  collars 
that  ride  upon  a  portion  of  the  upper  ends  of  the  columns.  These 
collars  are  anchored  to  the  lower  ends  of  the  columns  by  a  pair  of 
powerful  compression  springs.  Skids,  normally  3  inches  off  the 
ground,  are  depended  upon  to  absorb  any  excess  shock,  while  light 
double  skids  support  the  tail. 


316 


TYPES   OF  AEROPLANES  121 

The  wings  have  a  spread  of  37  feet  and  a  depth  of  8  feet  4  inches 
where  they  join  the  body,  giving  it  the  low  aspect  ratio  of  but  4.45 
to  1.  The  supporting  surface  measures  280  square  feet,  but  despite 
these  large  dimensions  the  total  weight  of  the  machine  scarcely  ex- 
ceeds 700  pounds,  which  is  a  tribute  to  its  construction.  The  curve 
of  the  wings  is  a  composite  one,  worked  out  from  calculations  by  the 
designer.  The  length  overall  of  the  machine  is  also  37  feet;  the  area 
of  the  fixed  tail  is  60  square  feet  and  that  of  the  horizontal  rudder,  or 
elevator,  22  square  feet.  The  greatest  care  has  been  taken  in  the 
construction  of  this  remarkable  monoplane  and  the  engineering  skill 
of  its  builder  is  discernible  in  the  many  ingenious  details  it  displays, 
many  of  them  never  having  been  employed  in  aeroplane  construction. 
This  machine  was  wrecked  through  an  unfortunate  accident  that 
had  no  bearing  on  its  design  or  construction.  It  was  rebuilt  late  in 
1911  with  numerous  detailed  improvements. 

H.  Farman  Monoplane.  A  radical  departure  from  current 
methods  of  construction  is  also  to  be  found  in  the  new  H.  Farman 
monoplane,  Figs.  54  and  55.  The  frame  is  a  triangular  structure 
united  at  the  forward  end  by  steel  girder  construction  in  the  form  of 
a  cross,  the  center  of  which  serves  as  the  support  for  the  shaft  of  the 
seven-cylinder  revolving  Gnome  motor.  The  four  main  frame  mem- 
bers are  connected  by  suitable  stanchions  and  are  trussed  with  piano 
wire;  they  are  not  joined  at  the  rear.  The  wings  are  not  mounted 
directly  on  this  framework  but  are  carried  almost  2  feet  above  it. 
This  places  the  power  plant  and  its  accessories,  as  well  as  the  aviator, 
on  a  lower  level  than  the  supporting  surface.  The  wings  are  mounted 
on  another  triangular  structure  which  also  serves  for  the  attachment 
of  the  running  gear-  At  right  angles  to  the  longitudinal  frame  mem- 
bers are  two  vertical  members,  attached  to  the  steel  girder  construc- 
tion on  the  forward  end  of  the  frame,  and  mounting  above  the  level 
of  the  wings  and  descending  considerably  below  the  level  of  the 
frame.  From  the  lowest  point  of  these  two  uprights  are  two  similar 
members  inclined  toward  the  rear,  attached  to  the  two  longitudinal 
members  of  the  frame  and  receiving  on  their  upper  extremities  the 
rear  transverse  girder  of  the  wing.  This,  as  can  be  seen  readily 
from  the  illustration,  forms  a  triangle,  or  really  two  triangles,  one  at 
each  side  of  the  frame,  the  apex  of  each  being  near  the  ground  and 
forming  the  support  for  the  axle  of  the  running  gear. 


317 


122  TYPES   OF  AEROPLANES 

The  rear  plane  is  mounted  directly  on  the  frame  with  the  rear 
portion  overhanging  to  allow  free  movement,  while  the  rudder  and 
vertical  fin  are  mounted  above  the  frame,  and  consequently  above 
the  horizontal  rudder.  There  are  neither  shock  absorbers  nor  main 
skids,  the  aeroplane  landing  on  two  small-diameter,  pneumatic-tired 
wheels  carried  on  a  rigid  steel  axle  passing  through  the  two  ends  of 
the  triangles  already  described.  A  simple  skid  is  used  at  the  rear  to 
prevent  the  tail  dragging  on  the  ground.  The  aviator's  seat  is  placed 
in  the  main  frame,  s  ightly  more  than  a  third  of  the  length  of  the 
machine  from  its  forward  end.  Placed  below  the  level  of  the  wings, 
the  pilot  is  more  advantageously  situated  to  correctly  estimate  his 
distances  for  landing  than  when  seated  above  the  wing  level.  This 
advantage  is  obtained  without  any  loss  of  protection  in  case  of  a  rough 
landing,  as  almost  half  the  machine  must  take  the  shock  before  the 
aviator  can  be  reached. 

Lateral  stability  is  obtained  by  the  usual  Farman  wing  tips,  or 
hinged  surfaces  attached  to  the  rear  outer  ends  of  the  main  planes, 
the  Farman  being  the  only  successful  French  monoplane  to  employ 
them.  The  Antoinette  was  originally  built  this  way,  but  later 
abandoned  wing  tips  in  favor  of  warping,  while  Bleriot,  Tellier,  and 
Hanriot  never  used  them.  The  spread  is  23  feet  6  inches;  depth, 
6  feet  6  inches;  aspect  ratio,  3.6  to  1,  which  is  extremely  low.  The  tail 
has  about  30  square  feet  of  surface,  making  the  total  about  190  square 
feet.  The  overall  length  is  26  feet  2  inches,  and  the  total  weight  of 
the  machine  alone,  660  pounds.  So  far  as  can  be  gathered  from  exam- 
ination, the  wing  curvature  is  the  same  as  for  the  standard  biplanes. 

Types  with  Fixed  Stabilizing  Plane.  Herring  Biplane.  As  is 
naturally  to  be  expected,  many  of  the  special  types  of  aeroplanes 
built  are  designed  with  a  view  to  providing  automatic  stability, 
thus  circumventing  the  Wright  patents.  In  the  Herring  machine, 
the  modification  takes  the  form  of  a  number  of  vertical,  triangular 
fins  mounted  on  the  upper  plane,  Fig.  56.  Each  of  these  vertical 
keels  has  about  2  square  feet  of  surface  and  there  are  six  of  them  all 
told,  two  being  equally  spaced  on  either  side  of  the  center  and  quite 
close  to  it,  wrhile  the  other  two  are  near  the  opposite  ends  of  the  upper 
main  plane.  When  an  aeroplane  tips  to  one  side,  it  has  a  tendency 
to  slide  to  the  ground  endwise,  but  as  the  weight  is  low  and  the  keels 
offer  resistance  to  this  sidewise  motion,  the  upper  part  of  the  machine 


318 


TYPES   OF   AEROPLANES 


123 


is  retarded,  while  the  lower  part  swings  over  like  a  pendulum  and 
equilibrium  is  regained. 


In  the  first  test,  made  in  the  spring  of  1910,  the  special  paraffine- 
coated  silk  surfaces  were  very  loose,  owing  to  the  dampness  and  fog, 


319 


124  TYPES   OF  AEROPLANES 

and  when  the  machine  was  in  the  air  it  was  necessary  for  the  aviator 
to  sit  well  to  the  left  to  counterbalance  a  difference  in  the  lifting 
power  of  the  two  sides  of  the  machine.  The  biplane  rose  readily 
after  a  run  of  85  feet  and  is  said  to  have  taken  to  the  air  at  a  speed  as 
low  as  22  miles  an  hour.  The  elevating  rudder  was  turned  too 
abruptly  and  the  machine  shot  40  feet  in  the  air  at  an  angle  of  almost 
30  degrees  from  the  horizontal.  After  flying  straightaway  about  300 
feet,  the  machine  made  a  successful  turn,  tilting  at  an  angle  of  about 
20  degrees,  and  making  a  40-degree  turn.  The  machine  weighed  only 
400  pounds,  while  the  aviator  weighed  190  pounds,  and  according 
to  the  inventor,  it  rose  with  a  propeller  thrust  of  only  140  pounds, 
while  he  believes  that  a  thrust  of  80  to  85  pounds  is  sufficient  to 
fly  it.  On  its  trial  flight,  the  motor  was  not  run  at  full  throttle  and 
was  thought  to  have  developed  only  9  horse-power,  which  would 
give  the  machine  as  a  whole  an  unusually  high  efficiency.  The  method 
of  maintaining  automatic  lateral  stability  appeared  to  work  fairly 
well  and  is  an  improvement  over  the  Voisin  in  that  the  head  resist- 
ance due  to  the  vertical  keels  is  reduced  to  a  minimum,  owing  to  their 
form  and  location. 

The  spread  of  this  Herring  biplane  is  only  28  feet;  depth, 
4  feet;  aspect  ratio,  7  to  1;  total  supporting  surface,  220  square  feet. 
A  25-horse-power,  four-cylinder  Curtiss,  air-cooled  motor  is  mounted 
on  the  lower  plane  at  the  rear  and  carries  on  its  crank  shaft  a  four- 
bladed,  6-foot  propeller  of  5-foot  pitch,  designed  especially  for  the 
machine  by  Mr.  Herring.  The  total  weight  is  about  400  pounds,  or 
with  its  inventor  590  pounds,  giving  it  a  pounds-per-horse-power 
factor  of  2.36,  and  a  loading  of  2.6  pounds  per  square  foot  of  surface. 
The  thrust  obtained  from  the  propeller  at  1,200  r.  p.  m.  is  said  to 
approximate  200  pounds.  A  double-surfaced  elevating  rudder  is 
carried  upon  hollow,  inclined  extensions  12  feet  in  front,  while  the 
single-surface  steering  rudder  is  similarly  placed  at  the  rear.  The 
machine  is  mounted  upon  a  central  runner  having  two  smaller  skids 
at  each  side,  there  also  being  another  skid  at  each  end  of  the  lower 
plane.  The  aviator  sits  in  a  small  seat  located  in  front  of  the  lower 
plane,  and  clings  to  two  inclined  braces  running  out  in  front  to  vertical 
struts  connecting  the  poles  that  support  the  elevating  rudder.  The 
latter  is  operated  by  a  foot  lever,  while  a  small  lever  at  the  right 
controls  the  steering  rudder. 


320 


TYPES   OF   AEROPLANES  125 

Baldwin  Biplane.  Another  modification  of  the  same  scheme 
is  incorporated  in  a  machine  built  by  Captain  Baldwin,  the  dean  of 
American  aviators.  This  consists  of  the  use  of  a  single,  rectangular 
stabilizing  plane  placed  vertically  at  the  center  and  above  the  upper 
main  plane,  as  the  Baldwin  is  also  a  biplane.  This  rudder  may  be 
turned  about  its  vertical  axis  by  means  of  a  yoke  fitting  around  the 
aviator's  shoulders  as  in  the  Curtiss  machine.  When  the  machine 
tips,  the  aviator  leans  to  the  high  side  and  sets  the  stabilizing  rudder 
at  an  angle  to  the  line  of  advance.  This  exerts  sufficient  force  to 
bring  the  machine  back  to  an  even  keel.  The  new  stabilizing  ruddar 
is  the  result  of  experiments  carried  out  by  the  Aerial  Experiment 
Association  several  years  ago  and  has  been  tried  by  Curtiss,  who 
claims  that  it  worked  satisfactorily  on  his  machine. 

The  Baldwin  biplane  has  a  spread  of  28  feet  and  a  depth  of  5 
feet;  aspect  ratio,  5.6  to  1;  total  area  of  main  planes,  280  square  feet. 
A  small,  horizontal  biplane  tail  is  carried  on  a  triangular  frame  extend- 
ing back  of  the  main  planes  and  mounted  on  a  skid.  The  vertical 
or  direction  rudder  is  placed  in  the  center  of  the  horizontal  rudder, 
or  tail.  The  arrangement  of  the  power  plant  and  aviator's  seat  is 
along  monoplane  lines,  the  motor  being  placed  at  the  front  edge 
of  the  lower  plane  and  the  aviator's  seat  above  the  rear  edge  of 
the  same  plane.  The  flywheel  of  the  motor  extends  above  and 
below  this  plane.  The  propeller  is  placed  half  way  between  the  main 
planes  and  is  driven  by  a  chain  and  sprockets.  It  is  about  8|  feet 
in  diameter  and  of  high  pitch.  The  regular  Curtiss  single  wheel  con- 
trol is  employed,  while  the  mounting  consists  of  a  pair  of  pneumatic- 
tired  wheels  in  front  and  a  single  skid  at  the  rear.  The  machine  has 
had  a  number  of  successful  tests  at  Hammondsport,  New  York. 

Waldon-Dyett  Monoplane.  Another  variation  of  the  idea  of 
utilizing  stationary  keels  to  attain  lateral  stability  is  found  in  the 
Waldon-Dyett  monoplane,  a  machine  of  American  design  and  con- 
struction. In  this  case,  the  keels  are  somewhat  similar  in  form  to  an 
old-time  kite — a  triangle  with  a  spherical  instead  of  a  flat  base.  These 
keels  are  about  18  to  20  inches  across  their  widest  part  and  taper 
back  sharply  to  a  point,  having  a  length  equivalent  to  the  depth  of 
the  main  plane  of  the  machine.  Two  of  them  are  employed,  one  at 
each  outer  edge  of  the  main  plane,  but  contrary  to  the  examples 
already  described,  they  are  set  at  an  angle  of  about  45  degrees  from 


321 


126  TYPES   OF   AEROPLANES 

the  "vertical  as  measured  from  the  tip  of  the  main  plane  to  the  keel. 
In  other  words,  they  both  lean  outward  at  the  same  angle.  It  will 
be  obvious  that  as  these  keels  are  rigidly  fixed  in  place,  they  form 
what  may  be  termed  "pockets"  at  each  end  of  the  main  supporting 
surface.  The  method  of  their  operation,  or  rather  the  role  they  are 
designed  to  play,  will  be  equally  apparent.  When  flying  straight 
ahead,  whether  on  an  even  keel,  ascending,  or  descending,  they  are 
neutral.  Should  the  machine  incline  to  the  right,  it  will  be  evident 
that  as  it  goes  downward  on  that  side  the  lower  surface  of  the  right 
keel  approaches  more  and  more  closely  to  the  horizontal  and  inter- 
poses a  correspondingly  increased  resistance  to  further  inclination. 
At  the  same  time  the  upper  surface  of  the  left  keel  presents  a  similarly 
increased  resistance,  tending  to  hold  that  end  down.  There  is  no 
manual  control  of  these  surfaces  by  the  aviator. 

HYDROAEROPLANES 

Advantages.  Ability  to  alight  upon  and  rise  from  the  water  as 
well  as  from  the  land  is  a  feature  that  the  aeroplane  must  possess 
before  it  can  be  said  to  completely  fulfill  its  mission.  Contrary  to  the 
general  impression,  water  is  quite  as  hard  and  unyielding  as  solid 
ground  when  struck  sharply  at  right  angles,  and  the  destructive 
effects  of  a  vertical  fall  from  any  height  would  scarcely  be  less  in 
striking  the  former  than  the  latter,  but  when  struck  at  an  angle  by 
a  properly-designed  surface  the  force  of  the  impact  is  very  greatly 
reduced  as  compared  with  a  ground  landing,  the  shock  of  which  must 
be  absorbed  by  the  springs  of  the  chassis.  It  is,  accordingly,  con- 
sidered much  safer  to  alight  upon  the  surface  of  the  water  than  it  is 
upon  the  ground.  But  the  ability  to  do  both  of  these  things  carries 
with  it  numerous  other  advantages.  There  are  few  parts  of  the 
country  where  flights  of  any  duration  would  not  carry  the  aviator 
over  lakes  and  streams,  and  in  making  long  flights  one  of  the  chief 
concerns  of  the  aviator  is  to  be  able  to  select  safe  landing  places,  so 
that  the  number  available  would  be  more  than  doubled.  Any  stretch 
of  water,  short  of  a  swift  running  slant  of  rapids,  affords  an  infinitely 
better  surface  than  the  most  carefully  leveled  field,  and  when  alight- 
ing in  strange  country,  the  aviator  always  can  be  certain  that  the 
surface  of  a  lake  does  not  hide  any  dangerous  pitfalls  in  the  form  of 
grass-covered  holes,  rocks,  and  ditches  that  are  seldom  lacking  in 


322 


TYPES   OF   AEROPLANES  127 

the  ordinary  field,  and  which  prove  so  destructive  to  the  chassis. 
Obstructions  of  a  serious  nature  all  appear  perfectly  flat  when  viewed 
from  above  so  that  a  field  which  may  have  the  appearance  of  a  velvety 
lawn  from  a  point  several  hundred  feet  over  it,  is  quite  the  reverse 
when  seen  from  the  ground,  and  quick  work  is  necessary  to  effect  a  safe 
landing  on  it.  Another  and  even  greater  advantage  is  to  be  found 
in  the  fact  that  the  wind  blowing  over  a  surface  of  water  is  much 
more  uniform,  usually  being  free  from  the  uncertain  puffs  and  gusts 
that  characterize  the  same  wind  blowing  over  the  adjacent  land. 
It  was  doubtless  for  this  reason  that  Langley  selected  the  Potomac 
River  as  the  site  of  the  first  flights  of  his  aerodrome. 

The  added  weight  of  both  a  landing  chassis  and  a  hydroplane 
float  for  alighting  on  the  water  naturally  forms  a  disadvantage,  but 
with  the  results  of  laboratory  experiments  now*  being  carried  out  at 
command  it  will  doubtless  be  possible  to  construct  an  aerocurve  or 
aerfoil,  as  it  is  variously  termed,  i.e.,  a  supporting  surface  that  will 
have  such  a  greatly  increased  efficiency  for  the  same  area,  that  the 
addition  of  a  hundred  pounds  or  more  will  call  for  no  appreciable 
increase  in  area.  Constructional  difficulties  are  also  involved  as  the 
hydroplane  floats  must  be  so  arranged  as  not  to  be  damaged  by  the 
yielding  of  the  springs  of  the  chassis  when  landing  on  the  ground. 
To  a  certain  extent,  there  always  will  be  a  demand  for  a  machine 
adapted  to  rise  from  and  alight  upon  the  water  alone,  such  as  the 
hydroaeroplanes  designed  for  naval  use,  and  the  experiments  of  the 
past  few  years  have  been  centered  on  the  development  of  a  machine 
for  this  purpose. 

Early  Attempts.  While  the  credit  for  constructing  the  first 
practical  hydroaeroplane  belongs  to  a  Frenchman,  M.  Fabre,  who 
brought  out  his  first  machine  only  a  few  years  ago,  the  subject  was 
investigated  in  this  country  several  years  previous.  This  was  at  a 
time  when  the  only  motors  available  were  unreliable  automobile 
types,  and  the  difficulty  encountered  in  keeping  the  engine  working 
for  any  length  of  time  caused  the  abandonment  of  the  experiments. 
Although  numerous  practical  flights  had  been  made  over  water 
prior  to  the  summer  of  1910,  some  of  them  of  quite  considerable 
distance,  the  precautions  taken  to  insure  the  floating  of  the  aeroplane 
in  case  it  should  drop  into  the  water,  were  always  of  a  makeshift 
nature,  intended  merely  for  the  particular  occasion.  For  instance, 


323 


128 


TYPES   OF   AEROPLANES 


Wilbur  Wright  in  preparing  for  his  flight  up  the  Hudson  from  Gov- 
ernor's Island,  lashed  a  canoe  beneath  the  biplane.  Curtiss  in  his  flight 
of  148  miles  down  the  Hudson  from  Albany  to  New  York,  made  use 
of  pontoons,  while  in  other  cases  air  cylinders  have  been  secured 
under  the  machine  to  insure  sufficient  buoyancy.  The  only  instance 
in  which  the  precautions  proved  necessary  was  in  the  case  of  Latham's 
first  attempt  to  cross  the  English  Channel  in  an  Antoinette  mono- 
plane. 

Fabre   Hydroaeroplane.    To  meet  conditions   of  this   nature, 
Fabre  designed  a  novel  monoplane,  Fig.  57,  capable  of  starting  from 


Fig.  57.     Fabre  Hydroaeroplane  in  Flight 

and  alighting  on  the  water.  It  can  also  navigate  the  surface  in  calm 
weather  in  case  of  damage  to  its  supporting  planes.  In  its  construc- 
tion, the  Fabre  hydroaeroplane  differs  radically  from  any  of  the  other 
designs,  in  fact,  it  is  thus  far  the  only  monoplane  of  its  kind.  The 
construction  consists  of  a  vertical  chassis,  analogous  to  that  of  a 
bicycle,  and  to  which  the  single  main  supporting  plane  is  fastened 
at  the  extreme  rear.  This  plane  is  in  two  sections  set  at  a  slight 
angle;  the  under  side  of  the  left-hand  section  being  shown  in  the 
figure.  The  motor  is  mounted  on  its  after  edge.  Forward  a  biplane 
elevating  rudder,  of  which  the  lower  plane  is  the  larger,  is  also  attached 
to  this  frame.  Immediately  above  the  biplane  rudder  forward  are 


334 


TYPES  OF  AEROPLANES  129 

two  twin  vertical  keels,  the  direction  rudder  being  placed  at  the 
center  of  the  main  plane,  just  where  the  sections  join  and  immediately 
forward  of  the  propeller,  where  its  leverage  is  greatly  increased  by 
the  rush  of  air  to  the  latter.  The  aviator's  seat  is  placed  directly  in 
the  center  of  the  frame.  The  cylindrical  gasoline  tank  is  placed 
directly  behind  the  aviator's  seat  and  is  suspended  between  the  guy 
wires  of  the  direction  rudder  aft  and  the  main  longitudinal  beam. 
Reference  to  the  figure  shows  that  there  is  less  framing  and  less  brac- 
ing on  this  monoplane  than  on  any  other  of  equal  size. 

The  complete  machine  rests  upon  three  hydroplane  floats,  one 
at  the  forward  end  of  the  chassis  and  the  two  others  under  the  main 
plane  half  way  between  the  center  and  the  two  ends.  These  hydro- 
planes are  of  the  Ricochet-Bonnemaison  type  in  which  the  bottom 
forms  a  hydroplane  surface.  But  while,  in  the  ricochet  boats  of 
Bonnemaison,  longitudinal  stability  is  obtained  by  placing  one  sur- 
face in  front  of  another,  and  joining  the  two  by  a  vertical  surface 
forming  a  notch,  in  this  case  the  front  plane  has  been  completely 
separated  from  the  rear  plane,  each  forming  the  bottom  of  a  separate 
float.  This  arrangement  has  the  advantage  of  giving  both  longitudinal 
and  lateral  stability,  while  the  fact  of  the  rear  plane  being  divided 
and  its  halves  placed  some  distance  apart  takes  them  out  of  the  dis- 
turbing influence  of  the  wake  of  the  forward  float.  In  addition,  as 
each  float  is  made  up  of  but  a  single  continuous  surface,  it  has  a  form 
offering  slight  resistance  to  the  air.  It  resembles  the  shape  of  the 
Antoinette  monoplane  wing.  The  resistance  to  the  air  that  the 
notch  would  give  is  thus  avoided,  and  the  float  performs  a  third 
function,  since  it  acts  as  an  auxiliary  supporting  surface  when  in  the 
air.  This  form  of  float  with  the  plane  surface  below  and  a  cylindrical 
surface  on  top  has  the  further  advantage  of  acting  like  a  hydroplane 
even  though  it  be  completely  submerged.  It  accordingly  does  not 
offer  any  great  resistance  when  engulfed  by  a  wave,  but  because  of  its 
speed  receives  a  more  energetic  upward  impulse  than  ever. 

The  chief  disadvantage  of  this  type  of  hydroplane  is  the  terrific 
pounding  it  receives  when  moving  rapidly  over  water  that  is  only 
slightly  disturbed.  The  portion  of  the  lifting  plane  in  contact  with 
the  water,  which  is  a  strip  of  only  a  few  square  inches  along  its  rear 
edge  when  the  plane  is  moving  rapidly,  is  instantly  increased  ten- 
fold the  moment  the  surface  is  no  longer  perfectly  smooth  and  level, 


325 


130  TYPES   OF   AEROPLANES 

because  of  the  slight  inclination  of  the  plane  to  the  horizontal.  The 
float  then  receives  upward  vertical  accelerations  equal  to  ten  times  its 
weight.  To  absorb  these  dangerous  shocks,  the  Fabre  hydroaeroplane 
floats  have  a  flexible  under  surface.  This  is  made  up  of  thin  veneered 
wood,  which  acts  in  the  same  way  as  the  head  of  a  drum.  By  this 
means,  even  the  framework  of  the  monoplane  is  protected  from  the 
shocks  of  the  waves,  in  the  same  manner  as  an  automobile  is  pro- 
tected from  jolting  of  the  road  through  its  pneumatic  tires.  More- 
over, very  great  flexibility  is  attained  between  the  body  of  the  float 
and  the  heavy  parts  of  the  apparatus.  As  may  be  seen  by  referring 
to  the  illustration,  Fig.  57,  the  elasticity  of  nearly  every  part  of  the 
machine  comes  into  play  to  absorb  the  upward  thrust  of  the  waves 
before  reaching  the  motor  or  the  aviator.  When  at  rest  on  the  surface, 
the  Fabre  hydroaeroplane  has  a  very  slight  draft,  not  exceeding 
25  centimeters  (9.8  inches),  decreasing  to  nothing  when  in  motion. 

The  tapering  form  of  the  bottom  of  the  floats  permits  them  to 
pass  over  wreeds,  ropes,  and  other  floating  bodies,  or  to  skim  over 
shoals  without  danger,  even  at  high  speed.  No  motor  boat  has  such 
ease  of  evolution  in  shallow  water  as  a  hydroplane  driven  by  an 
aerial  propeller.  This  is  true  to  an  extent  where  it  holds  good  even 
if  there  be  no  water.  If  the  Fabre  marine  aeroplane  should  land  on 
a  meadow  it  would  not  be  injured  as  the  floats  are  sufficiently  solid 
to  act  as  skids.  A  device  is  being  perfected  to  permit  it  to  land  or 
start  either  on  the  water  or  on  the  ground.  The  floats  are  capable 
of  resisting  the  action  of  salt  water,  as  a  test,  one  having  remained 
afloat  for  two  months  without  damage. 

The  wings  of  this  aeroplane  are  stretched  upon  a  special  steel 
truss  of  the  same  form  that  Fabre  has  employed  in  the  Paulhan 
biplane  just  described,  and  the  wings  themselves  are  capable  of  being 
reefed  or  folded  when  the  machine  is  at  rest  on  the  water  as  the 
machine  might  otherwise  be  damaged  by  the  wind.  The  wing  itself 
is  composed  of  four  parts,  somewhat  analogous  to  a  bird's  wing: 

(1)  A  trussed  longitudinal  girder  is  placed  along  the  front  edge  in 
the  position  which  the  bones  occupy  in  a  bird's  wing.  This  is  the 
only  longitudinal  support  of  the  wing  and  it  is  depended  upon  to 
give  rigidity  to  the  whole  construction  so  that  it  is  very  strongly 
reinforced.  The  uprights  to  which  the  floats  are  fastened  are  attached 
directly  to  it.  This  zigzag  form  of  girder,  which  is  a  newly  patented 


336 


TYPES   OF   AEROPLANES  131 

construction,  is  used  not  only  for  the  wings  and  horizontal  rudders, 
but  also  for  the  members  of  the  chassis,  and  for  the  framework  of 
the  hydroplanes;  in  a  word,  the  whole  apparatus  is  essentially  a 
Fabre  reinforced  beam. 

(2)  The  ribs  which  correspond  to  the  quill  feathers  of  a  bird's 
wing,  consist  of  thin  strips  of  wood  superposed  and  glued  together. 
They  fit  into  sockets  on  the  bottom  of  the  single  longitudinal  girder. 

(3)  The  covering  of  the  wing  consists  of  "simili-silk,"  such  as 
is  used  for  the  light  sails  of  racing  yachts.     This  is  hemmed  and 
reinforced  at  the  edges  and  provided  with  eyelets  and  grummets, 
permitting  it  to  be  laced  on,  so  that  it  may  be  quickly  removed  with- 
out dismounting  any  part  of  the  skeleton  of  the  wing.     Pockets 
corresponding  to  the  position  of  the  ribs  are  sewed  into  the  cloth  and 
the  latter  is  drawn  on  over  them  and  then  laced  to  the  main  girder, 
wood  eyelets  being  employed  for  this  purpose,  while  at  the  rear  it  is 
held  taut  by  ingenious  spring  clamps. 

(4)  Suitable  braces  are  provided  for  holding  the  main  beams  of 
the  wings  against  turning  in  their  sockets  when  the  machine  is  in 
flight.    Steel  cables  fastened  to  the  lower  ends  of  these  braces  serve 
to  regulate  the  angle  of  incidence  of  the  wings  or  to  warp  them.    The 
wings  themselves  are  also  trussed  with  similar  braces. 

The  spread  is  approximately  47  feet,  depth  6  feet,  aspect  ratio 
7.4  to  1,  total  area  about  280  square  feet,  pounds  per  horse-power 
5.6.  The  total  weight  in  flight  is  about  950  pounds,  giving  it  a  load- 
ing of  3.4  pounds  per  square  foot.  The  power  plant  consists  of  a 
50-horse-power,  seven-cylinder  revolving  Gnome  motor,  directly 
attached  to  an  8J-foot,  two-bladed  wood  propeller  which  it  drives 
at  1,100  r.p.m. 

The  Fabre  hydroaeroplane  made  its  first  flight  at  Martigues, 
France,  March  28,  1910.  It  attained  a  speed  of  34.2  miles  (55  kilo- 
meters) an  hour  on  the  surface,  and  then  flew  about  7  feet  above  the 
water  for  a  third  of  a  mile.  Later  it  made  a  longer  flight  at  a  height 
of  about  10  feet  above  the  surface.  On  May  17,  a  series  of  flights 
were  made  by  Henri  Fabre  before  Paulhan.  The  machine  rose 
easily  and  gracefully  from  the  water  and  made  a  splendid  flight  of 
about  4  miles  at  a  height  of  65  feet.  In  coming  down,  however,  the 
aviator  volplaned  at  too  great  an  angle  and  landed  with  a  terrific 
splash,  throwing  Fabre  head  first  out  of  his  seat  but  not  injuring  him. 


327 


132 


TYPES   OF   AEROPLANES 


Under  similar  conditions  on  land,  such  a  descent  would  have  meant 
not  only  the  total  wreck  of  the  machine  but  in  all  probability  the 
death  of  the  aviator.  As  it  was,  the  only  damage  suffered  was  a  duck- 
ing and  the  breakage  of  one  end  of  a  wing  and  one  of  the  floats. 

Curtiss  Hydroaeroplane.  The  most  persistent  as  well  as  the 
most  successful  experimenter  in  this  field  in  America  has  been  Glenn 
H.  Curtiss.  He  first  began  his  investigations  in  the  early  part  of  1910 
by  attaching  floats  to  one  of  his  standard  type  biplanes,  but  did  not 
find  it  possible  to  attain  a  speed  in  excess  of  20  miles  per  hour,  which 
was  not  sufficient  to  permit  the  machine  to  rise  from  the  surface. 
Winter  cut  short  these  experiments  which  were  carried  out  at  Ham- 
mondsport,  New  York,  the  site  of  the  Curtiss  factory,  and  they  were 
shortly  after  transferred  to  San  Diego,  where  he  was  engaged  at  the 
time  in  instructing  several  army  and  navy  officers  in  flying. 


<ELEVA7~M6   HYDROPLANE  %4//V  POrtTOOM 

Fig.  58.     Side  Elevation  of  Early  Curtiss  Hydroaeroplane 

First  Flights.  In  his  first  experiments  on  the  Pacific  Coast' 
Curtiss  followed  the  Fabre  design,  so  far  as  the  form  of  the  floats 
was  concerned.  One  large  float,  or  hydroplane,  6  feet  wide,  5  feet 
from  front  to  rear,  and  1  foot  thick  at  its  central  section,  was  con- 
structed and  placed  under  the  center  of  the  machine.  The  bottom 
of  this  float  was  perfectly  flat  and  was  fixed  at  an  angle  of  10  to  12 
degrees.  Some  distance  forward  of  the  main  float,  at  about  the  same 
position  as  the  front  wheel  of  the  chassis  of  the  land  machine,  another 
float  6  feet  wide,  1  foot  from  front  to  rear,  and  6  inches  deep,  was 
placed;  while  at  the  extreme  forward  end  of  the  biplane  there  was 
mounted  a  small  elevating  hydroplane  measuring  6  feet  wide  by  8 
inches  fore  and  aft  and  1|  inches  thick.  This  hydroplane  was  carried 
on  a  special  outrigger  and  was  fixed  at  an  angle  of  about  25  degrees, 
in  order  to  lift  the  forward  end  of  the  machine,  a  spray  shield  being 
fitted  just  behind  it  to  keep  the  aviator  dry  when  skimming  over 
the  surface.  The  location  of  these  three  hydroplanes,  as  well  as  their 


TYPES   OF   AEROPLANES 


133 


relative  angles  of  incidence,  are  plainly  shown  in  the  side  elevation, 
Fig.  58. 

It  was  found  that  while  these  floats  caused  considerable  disturb- 
ance of  the  water,  especially  at  low  speed,  there  was  no  difficulty  in 
attaining  a  speed  of  45  miles  an  hour  on  the  surface.  At  as  low  a 
rate  of  travel  as  10  miles  an  hour,  the  hydroplanes,  which  are  nor- 
mally submerged  when  the  machine  is  at  rest,  rose  to  the  surface, 
and  as  the  speed  increased,  only  the  rear  edges  of  the  two  main  floats 
were  required  to  support  the  machine.  The  aeroplane  readily  attained 
sufficient  speed  to  rise  in  the  air,  for,  as  the  speed  increased  and  the 
floats  emerged  from  the  water,  their  head  resistance  diminished, 


Fig.  59.     Diagram  of  Pontoon  on  Curtiss'  Latest  Hydroaeroplane 

and  there  were  only  the  skin  friction  of  the  water  on  a  very  small 
area,  plus  the  air  resistance,  to  be  overcome. 

At  the  first  try-out,  while  traveling  over  the  water  at  a  high  rate 
of  speed,  Curtiss  found  himself  approaching  the  land,  and  to  avoid 
running  ashore,  he  turned  the  horizontal  rudder  sharply  upward, 
with  the  result  that  the  machine  rose  from  the  water  with  perfect  ease. 
Succeeding  flights  demonstrated  that  there  was  no  difficulty  in  arising 
from  the  water  and  alighting  upon  it  as  often  as  desired.  The  machine 
developed  a  maximum  speed  of  50  miles  an  hour  in  the  air,  as  com- 
pared with  45  miles  per  hour  on  the  surface  of  the  bay.  But  the  great 
fuss  stirred  up  by  these  original  floats  as  the  machine  got  under  way 
preparatory  to  rising,  and  the  fact  that  they  were  not  suited  to  any- 
thing but  a  calm  surface,  caused  them  to  be  discarded  shortly  after- 


329 


134 


TYPES   OF   AEROPLANES 


ward.  They  were  replaced  by  a  large  single  float,  12  feet  long  by  2  feet 
wide  and  12  inches  deep,  Fig.  59.  This  was  built  entirely  of  wood  and 
resembles  a  common  flat-bottomed  boat  or  scow,  the  top  being 
covered  with  canvas  to  prevent  the  entrance  of  water.  Three  feet 
from  the  forward  end,  the  bottom  curved  upward  sharply,  forming  a 
smooth  bow  the  entire  width  of  the  float,  while  at  the  rear  it  was 
inclined  downward  in  a  similar  manner.  This  single  float  is  placed 
under  the  biplane  in  such  a  position  that  the  major  portion  of  the 
weight  of  the  machine  and  the  aviator  is  slightly  aft  of  the  center  of 


Fig.  00.      Curtiss  Hydroaeroplane  About  to  Rise  from  the  Water 

the  float,  which  causes  the  latter  to  rise  slightly  forward  when  resting 
normally  on  the  surface,  thus  providing  the  necessary  angle  for 
hydroplaning.  The  weight  of  the  new  float  is  but  50  pounds,  or  less 
than  half  that  of  the  two  large  floats  previously  employed.  Trials 
of  the  biplane  fitted  with  the  new  floats  showed  an  astonishing  differ- 
ence in  the  amount  of  disturbance,  practically  no  commotion  being 
caused  even  when  the  machine  was  just  getting  under  way,  while 
the  aeroplane  rose  from  the  surface  even  more  readily  than  before. 
Fig.  60  shows  one  of  this  type  just  getting  under  way.  Besides 
being  much  more  compact  and  creating  less  resistance,  this  new 
float  can  also  be  employed  for  carrying  articles  or  a  passenger. 


330 


TYPES   OF   AEROPLANES 


135 


In  order  to  prevent  the  aeroplane  from  listing,  or  tilting  to  one  side 
or  the  other,  an  inclined  brace  4  feet  long  by  3  inches  wide,  is  fastened 
to  the  front  edge  of  the  lower  plane  at  each  end.  Attached  to  each 
of  these  braces  is  an  inflated  rubber  tube  to  give  extra  buoyancy  to 
the  ends  of  the  machine,  should  it  be  tilted  sufficiently  to  submerge 
them  when  skimming  over  the  surface.  By  the  use  of  these  " water 
props"  the  aeroplane  is  prevented  from  wabbling  from  side  to  side, 
even  though  the  main  supporting  plane  is  but  two  feet  in  width.  A 
number  of  flights  made  with  this  arrangement  demonstrated  the 
necessity  of  altering  the  balance  of  the  biplane,  and  the  motor  and 


Fig.  61.      Latest  Model  of  Curtiss  Hydroaeroplane  Showing  Two  Propellers  and 
V  Engine  Ahead  of  Operator 

propeller  were  accordingly  placed  forward  while  the  aviator's  seat 
was  located  at  the  rear  of  the  main  plane,  just  the  reverse  of  the 
standard  Curtiss  machine. 

All  of  Curtiss'  experimenting  with  the  hydroaeroplane  was 
carried  out  with  what  was  practically  a  standard  biplane  of  his  own 
make,  mounted  upon  floats.  As  the  result  of  the  experience  thus 
gained,  he  subsequently  designed  a  machine  specially  for  this  service. 
This  is  shown  in  Fig.  61,  and  the  radical  departure  it  represents 
from  the  standard  Curtiss  type  will  be  apparent  at  a  glance.  Instead 
of  the  single  propeller  at  the  rear,  two  tractor  screws  are  employed. 
These  are  carried  in  bearings  mounted  on  twin  steel  tubular  struts 


331 


136  TYPES   OF  AEROPLANES 

and  are  driven  through  chains  running  in  steel  tubes  by  an  eight- 
cylinder,  V-type,  water-cooled  motor  placed  in  the  forward  part  of 
the  boat  or  hydroplane  float.  Twin  steel  tubular  struts  are  also 
employed  to  reinforce  the  structure  just  back  of  the  propeller  sup- 
ports. The  lower  plane  is  cut  away  at  the  center  and  the  aviator's 
seat  is  placed  in  the  boat,  bringing  the  center  of  gravity  of  the  biplane 
very  low.  Tubular  braces  are  run  from  each  side  of  the  boat  to  points 
on  the  under  side  of  the  lower  plane,  and  fastened  to  the  steel  plates 
holding  the  propeller  supporting  struts,  while  bamboo  braces  run 
from  the  upper  plane  to  the  bow  of  the  boat  on  either  side,  thus 
stiffening  the  entire  structure.  Both  the  elevator  and  the  direction 
rudder  are  placed  at  the  rear,  the  remainder  of  the  construction  not 
differing  particularly  from  the  standard  Curtiss  machine.  Some 
very  successful  flights  have  been  made  with  this  hydroaeroplane. 
Naval  Trials  with  Improved  Type.  A  great  many  very  successful 
flights  were  made  with  this  Curtiss  hydroaeroplane  as  redesigned, 
the  chief  of  these  being  the  flight  made  by  Curtiss  over  San  Diego 
Bay  from  North  Island  to  the  U.  S.  S.  Pennsylvania.  He  alighted 
upon  the  surface  alongside  the  cruiser  and  the  machine  was  hoisted 
aboard  by  means  of  one  of  the  launch  cranes.  In  addition  to  the 
reversed  positions  of  the  motor  and  aviator,  numerous  other  changes 
were  made,  so  that  the  machine  is  really  a  special  type  in  itself. 
The  front  horizontal  or  elevating  rudder  of  the  Curtiss  machine  was 
removed  entirely,  and  a  special  twin  V-finned  tail  with  a  vertical 
fin  in  the  center  placed  at  the  after  end  of  a  tail  frame,  similar  in 
appearance  to  the  fuselage  framing  of  the  French  monoplanes. 
Stabilizing  fins  running  from  the  lower  main  plane  to  the  props 
already  described,  were  also  added.  Special  balancing  planes  were 
also  placed  at  the  rear  of  the  main  planes,  half  way  between  them  and 
the  float  underneath.  The  removal  of  the  forward  elevating  rudder 
made  it  possible  to  hoist  the  aeroplane  aboard  the  vessel  so  that  the 
aviator  could  climb  on  the  deck,  the  modified  design  of  the  machine 
making  it  particularly  adaptable  for  naval  work,  though  Mr.  Curtiss 
did  not  like  the  arrangement  owing  to  the  blast  of  air  from  the  pro- 
peller constantly  striking  his  face  and  the  interference  with  his  view 
forward  caused  by  the  new  location  of  the  motor.  The  demonstra- 
tion so  favorably  impressed  the  naval  authorities  that  a  new  machine 
of  this  type  has  since  been  purchased  from  the  Curtiss  factory  and 


332 


TYPES   OF  AEROPLANES  137 

a  number  of  naval  officers  were  trained  in  its  handling  at  Hammonds- 
port  during  the  summer  of  1911.  On  one  trial  Lieutenant  Ellyson, 
the  navy's  first  qualified  aviator,  carried  Captain  Chambers,  in 
charge  af  the  aeronautical  work  of  the  navy,  on  a  flight  the  length  of 
Lake  Keuka,  a  distance  of  40  miles,  while  on  a  measured  course  the 
machine  covered  16  miles  in  18  minutes,  carrying  the  two  officers. 
Trials  were  later  transferred  to  the  Chesapeake,  where  Lieutenants 
Ellyson  and  Towers,  of  the  Naval  Aviation  Corps,  flew  140  miles 
from  Annapolis  to  Fortress  Monroe  in  two  hours  twenty-seven 
minutes,  or  at  the  rate  of  close  to  60  miles  an  hour.  For  most  of 
the  distance  an  elevation  of  1,000  feet  was  maintained.  The  machine 
was  fitted  with  a  new  device  brought  out  during  the  summer  of 
1911,  which  permits  either  the  pilot  or  the  aviator  to  assume  control 
of  the  machine  as  desired.  During  the  flight  in  question,  the  officers 
frequently  shifted  the  control  wheel  from  one  to  the  other,  demon- 
strating the  rapidity  and  effectiveness  with  which  the  change  could 
be  made. 

In  order  to  utilize  the  advantages  of  the  aeroplane  for  naval 
service  to  the  fullest  extent,  a  simple  and  rapid  method  of  launching 
the  machine  from  the  vessel,  without  the  necessity  of  encumbering 
the  deck  with  special  contrivances  for  that  purpose,  is  essential,  so 
that  the  later  experiments  carried  out  at  Hammondsport  with  this 
end  in  view  were  of  far  greater  importance  than  the  most  successful 
flights.  Lieutenant  Ellyson  has  devised  a  method  by  which  a  hydro- 
aeroplane may  be  launched  at  sea  directly  from  the  vessel,  without 
the  loss  of  time  necessary  to  put  it  overboard  and  permit  it  to  rise 
from  the  surface  of  the  water.  Heavy  seas  often  continue  for  some 
time  after  the  wind  occasioning  them  has  subsided,  and  under  such 
conditions,  it  would  not  be  safe  to  launch  an  aeroplane  from  the  side 
of  the  vessel,  though  it  might  be  quite  feasible  for  the  machine  to 
return  alongside  and  be  hoisted  aboard,  after  having  taken  flight 
directly  from  the  vessel  itself.  The  new  method  simply  calls  for  the 
use  of  cables  stretched  from  the  boat  deck  or  superstructure  of  the 
ship,  to  the  bow.  One  of  these  is  a  main  wire  cable  down  which 
the  aeroplane  slides  to  gather  momentum  for  rising,  while  the  others 
are  merely  auxiliary  wires  at  the  sides  and  parallel  to  the  main  cable, 
to  maintain  the  machine  in  balance  on  the  latter  during  its  down- 
ward slide.  These  auxiliary  wires  support  the  outer  ends  of  the  wings 


333 


138  TYPES   OF   AEROPLANES 

until  the  machine  acquires  sufficient  headway  to  maintain  its  own 
equilibrium  by  means  of  its  balancing  planes.  This  rigging  does  not 
interfere  in  any  way  with  the  working  of  the  armament  and  is 
arranged  so  that  it  can  either  be  left  permanently  in  place  ready 
for  immediate  use,  or  may  be  quickly  stowed  away,  the  cables 
simply  being  hooked  in  heavy  eye  bolts  and  stretched  taut 
to  make  them  ready  for  use.  This  system  enables  the  machine  to 
be  launched  when  a  high  sea  would  make  it  impossible  to  arise 
directly  from  the  surface  after  being  lowered  overboard.  The  experi- 
ments carried  out  at  San  Diego  in  connection  with  the  U.  S.  S. 
Pennsylvania  demonstrated  that  the  hydroaeroplane  could  be  landed 
alongside  and  hoisted  aboard  in  a  wind  of  10  knots  and  with  a  4-knot 
tide  running,  the  sea  conditions  being  too  rough  for  successful 
launching.  Ability  to  get  away  from  the  ship  at  the  crucial  moment 
is  regarded  as  being  by  far  the  most  important  point  in  the  prac- 
tical use  of  the  aeroplane  by  the  navy,  since  the  wrecking  or  even 
the  loss  of  the  machine  after  the  desired  information  had  been  obtained 
would  be  considered  of  minor  importance.  With  the  new  launching 
apparatus,  it  is  also  possible  for  the  ship  to  steam  head  into  the  wind 
at  any  desired  speed,  thus  securing  the  necessary  conditions  for 
quick  launching. 

To  thoroughly  test  this  method,  a  platform  was  erected  150 
feet  from  the  shore  of  Lake  Keuka  and  the  necessary  cables  stretched 
from  it  to  the  water.  The  main  cable  was  a  f-inch  steel  rope 
made  fast  to  a  pile  driven  in  the  lake  250  feet  distant  and 
submerged  so  that  the  aeroplane  could  pass  over  it  without  dam- 
age. The  machine  employed  was  the  regulation  navy  type  of 
Curtiss  hydroaeroplane,  equipped  with  a  75-horse-power  motor, 
fitted  with  the  new  Curtiss  double  control  system  and  capable  of 
carrying  two  persons  at  high  speed.  Its  total  weight  is  1,200  pounds. 
The  bottom  of  the  pontoon  under  the  hydroaeroplane  carries  a 
grooved  runner,  1  inch  wide  by  If  inches  deep,  lined  with  sheet  iron 
throughout  its  length  and  reinforced  with  iron  bands  at  each  end  to 
form  a  durable  bearing  surface,  while  the  outer  ends  of  each  lower 
plane  were  equipped  with  light  irons,  forming  a  bearing  surface  to 
engage  the  balancing  wires  strung  on  either  side  of  the  main  support- 
ing cable.  The  main  cable  was  passed  over  a  pair  of  shears  16  feet 
high,  and  fitted  with  a  small  platform  from  which  the  motor  of  the 


334 


TYPES   OF  AEROPLANES  139 

machine  could  be  started.  The  grade  was  about  10  per  cent.  A 
simple  releasing  device  was  provided  to  start  the  machine  on  its 
downward  slide,  this  consisting  of  a  short  length  of  rope  fastened  to 
the  bow  of  the  pontoon  (also  variously  termed  the  float  or  hydro- 
plane) and  fitted  with  an  eye  through  which  passes  a  toggle  pin  con- 
necting this  short  piece  with  a  rope  made  fast  to  the  legs  of  the  shears. 
A  sharp  jerk  on  this  rope  pulled  the  toggle  pin  and  released  the 
machine,  which  quickly  gathers  headway  under  the  combined  force 
of  gravity  and  the  thrust  of  the  propeller.  During  the  trials,  the 
machine  was  first  floated  on  the  lake  and  then  hauled  up  on  the 
cable.  The  prevailing  wind  was  about  10  miles  an  hour,  its  direction 
slightly  quartering  against  the  line  of  flight,  the  trial  apparatus  natur- 
ally not  possessing  the  mobility  of  a  vessel  at  sea,  as  the  latter  could 
always  be  headed  directly  into  the  wind.  In  the  first  trials,  two  men 
held  lines  running  to  the  outer  ends  of  each  wing  to  make  certain 
that  the  machine  would  maintain  its  balance  until  sufficient  head- 
way was  gained,  but  this  assistance  was  found  unnecessary.  The 
machine  rose  easily  from  the  cable  after  having  traveled  a  distance 
of  about  150  feet,  attaining  a  speed  of  30  miles  an  hour  just  before 
lifting.  Numerous  trials  were  carried  out  with  unvarying  success, 
demonstrating  that  the  length  of  cable  required  is  so  short  as  to  make 
the  fitting  of  the  new  launching  apparatus  possible  even  on  the 
smallest  cruisers,  as  with  the  advantage  of  the  head  wind  created  by 
the  speed  of  the  vessel,  the  aeroplane  could  rise  almost  directly  from 
the  cable  without  having  to  take  advantage  of  the  full  force  of  gravity 
by  gliding  down  ^its  entire  length  before  beginning  its  flight.  "  In  the 
opinion  of  Captain  Chambers,  another  year  will  see  the  hydro- 
aeroplane developed  to  such  an  extent  that  each  battleship  of  the 
American  navy  may  have  its  own  flying  machine. 

Combination  Land  and  Water  Type.  Since  bringing  out  the  type 
of  hydroaeroplane  purchased  by  the  navy,  Curtiss  has  been  experi- 
menting with  still  further  improvements,  the  new  machine  being 
equipped  with  wheels  in  addition  to  the  large  float.  There  are  only 
two  of  these  wheels,  one  at  either  side  of  the  float  about  under  the 
center  of  the  lower  main  plane,  the  forward  third  wheel  of  the  stand- 
ard machine  having  been  discarded.  These  wheels  are  pulled  up  out 
of  the  way  by  means  of  a  hinged  brace  which  runs  from  the  wheel 
hubs  to  the  front  beam.  The  elevating  rudder  has  been  placed 


335 


140  TYPES   OF   AEROPLANES 

extremely  low,  at  a  level  about  midway  between  the  lower  main 
plane  and  the  deck  of  the  pontoon,  while  there  is  also  a  small  auxiliary 
hydro-surface  just  forward  of  the  pontoon  and  under  its  bow.  A 
Curtiss  standard  eight-cylinder,  V-type,  50-horse-power  motor  sup- 
plies the  energy  and  drives  the  machine  at  a  speed  of  45  to  50  miles 
an  hour  over  the  water. 

Curtiss  Family  Hydroaeroplane.  As  the  result  of  his  success  in 
developing  the  hydroaeroplane  for  naval  use,  Mr.  Curtiss  has  brought 
out  a  type  designed  for  pleasure  flying.  Owing  to  the  fact  that  it  is 
intended  to  carry  several  passengers,  this  has  been  dubbed  the 
"family  hydro."  It  consists  of  a  standard  Curtiss  biplane  mounted 
directly  on  a  single  open  boat  of  unusual  size  without  any  inter- 
mediate framing,  so  that  the  lower  plane  rests  directly  on  top  of  the 
boat  amidships.  The  passengers  are  seated  in  the  bow  of  the  boat 
just  forward  of  the  main  lower  plane,  while  the  motor  is  mounted 
just  underneath  the  upper  plane,  so  as  to  allow  the  propeller  sufficient 
clearance  over  the  back  of  the  boat  and  keep  it  out  of  the  spray 
thrown  up  when  the  machine  is  skimming  the  surface  rapidly.  The 
side  floats,  or  inflated  tubes,  employed  on  the  previous  machines  to 
maintain  them  in  lateral  balance  when  skimming,  are  also  a  feature 
of  the  new  passenger-carrying  hydroaeroplane,  which  is  said  to 
handle  as  easily  and  safely  as  a  fast  motorboat,  while  having  the 
advantage  of  the  latter  in  that  its  lifting  ability  permits  it  to  travel 
over  rough  water  or  to  rise  above  it  entirely.  It  is  also  capable  of 
rising  from  and  alighting  upon  the  ground  as  well  as  on  the  water, 
as  it  is  equipped  with  the  folding  two-wheel  chassis  just  described 
in  connection  with  another  type  of  Curtiss  hydroaeroplane. 

Burgess  Hydroaeroplane.  It  was  only  natural  that  W.  S. 
Burgess,  the  well-known  yacht  designer,  who  some  time  ago  forsook 
that  field  to  take  up  the  building  of  the  Burgess- Wright  biplanes, 
should  also  devote  attention  to  the  development  of  the  hydroaeroplane. 
So  far  as  the  machine  itself  is  concerned,  it  is  of  the  usual  Burgess- 
Wright  two-propeller  headless  type,  driven  by  a  four-cylinder  motor. 
The  water  supporting  surface  consists  of  two  hydroaeroplanes  14 
feet  wide  by  2  feet  long  and  having  a  draft  of  10  inches  at  their  deepest 
point.  They  are  designed  to  meet  the  water  so  as  to  create  the 
minimum  of  head  resistance  or  disturbance  and  are  fastened  com- 
paratively close  together  under  the  center  of  the  machine.  They 


336 


TYPES   OF   AEROPLANES  141 

are  of  the  single-step  hydroplane  type  much  used  in  racing  motor- 
boat  design  and  are  heavily  trussed  and  reinforced  to  give  them  a 
high  factor  of  safety.  The  first  trials  of  the  new  machine  showed  it 
to  be  very  speedy  on  the  surface  and  with  ample  lifting  power  to 
raise  the  boats  from  the  water.  During  one  trial,  Mrs.  F.  G.  Macom- 
ber,  Jr.,  was  carried,  she  being  the  first  woman  to  make  a  flight  in  a 
hydroaeroplane  over  the  Atlantic.  Flights  were  made  under  varying 
conditions  ranging  from  a  perfect  calm  to  a  25-mile  wind,  and  it 
was  noticeable  that  the  winds  which  would  bother  a  skilled  aviator 
over  the  uneven  ground  gave  the  novice  no  concern  in  the  new  hydro- 
aeroplane over  the  water.  In  fact,  the  advantage  is  so  great  that 
doubtless  most  of  the  teaching  henceforth  at  the  Burgess  school 
will  take  the  form  of  over-water  flights,  as  one  of  the  greatest  diffi- 
culties that  both  the  manufacturer  and  the  instructor  have  had  to 
encounter  is  that  of  impressing  upon  the  untrained  novice,  the 
importance  of  attempting  to  fly  only  in  the  most  favorable  weather. 
Brown  Hydroaeroplane.  A  departure  from  either  of  the  fore- 
going types  is  found  in  the  Brown  hydroaeroplane  which  was  built 
on  the  Chesapeake  and  has  been  successfully  flown  there.  The 
aeroplane  itself  is  of  the  original  Henri  Farman  type,  having  ailerons 
attached  to  the  outer  rear  trailing  edges  of  both  main  planes,  direc- 
tion rudder  at  the  rear,  elevator  of  the  single-plane  type  in  front,  and 
the  propeller  at  the  rear  edge  of  the  lower  main  plane,  the  aviator 
sitting  just  forward  of  the  motor.  The  spread  is  32  feet  and  the 
length  31  feet,  the  planes  themselves  being  3J  feet  wide,  while  the 
distance  between^  them  is  4J  feet,  this  also  representing  the  chord. 
The  main  planes  are  constructed  in  five  sections  and  can  be  removed 
or  replaced  without  the  necessity  of  rebuilding  an  entirely  new  upper 
or  lower  main  plane,  as  is  usually  the  case.  The  camber  of  the  curve 
is  3  inches  and  it  is  located  one  third  of  the  distance  back  from  the 
forward  edge.  Power  is  supplied  by  a  45-horse-power  motor  directly 
driving  a  7-foot  6-inch  propeller  with  a  5.9-foot  pitch.  The  power 
plant,  fuel,  and  water  weigh  about  450  pounds,  and  the  hydroplanes 
and  their  braces  175  pounds,  the  complete  weight  being  1,000  pounds. 
There  are  three  supporting  hydroplanes  with  a  total  displacement  of 
27  cubic  feet.  They  are  designed  with  such  an  easy  bow  curve  that 
they  would  skim  the  surface  after  the  machine  had  not  gone  more 
than  50  feet,  and  would  leave  the  water  the  moment  the  machine 


337 


142  TYPES   OF   AEROPLANES 

attained  a  good  speed.  The  first  hydroplanes  employed  were  of 
sheet  metal  and  of  crude  construction,  but  in  spite  of  this  drawback 
the  machine  showed  itself  capable  of  40  to  50  miles  an  hour  on  the 
surface  and  52  miles  an  hour  in  the  air. 

Detroit  Flying  Fish.  A  type  of  machine  that  is  part  hydro- 
plane and  part  aeroplane  is  that  recently  placed  on  the  market  by  a 
Detroit  manufacturer,  Fig.  62.  It  is  aptly  termed  the  "flying  fish", 
as  it  is  designed  to  do  most  of  its  travel  by  skimming  over  the  water, 
seldom,  if  ever,  rising  more  than  8  or  10  feet  above  the  surface.  It 
consists  of  a  water-tight  steel  and  aluminum  tank,  2  feet  deep,  5 


Fig.  62.     Detroit  Flying  Fish 

feet  7  inches  wide,  and  7  feet  2  inches  long.  This  tank,  or  pontoon, 
has  a  sloping  bow,  but  is  otherwise  square.  Mounted  on  this  pon- 
toon on  steel  tubing  supports,  about  6  feet  high,  are  monoplane 
wings,  or  rather  a  single  plane  of  26  feet  spread  by  6  feet  6  inch 
depth.  The  supporting  surface  is  of  oil-treated  canvas.  The  hori- 
zontal and  vertical  rudders  are  combined,  the  four-vaned  plane  of 
canvas  being  mounted  at  the  end  of  a  steel  tube  frame.  This  is  the 
machine's  aerial  tail.  Extending  back  of  the  hull  and  connected  with 
the  frame  above  it  by  tubing,  is  the  marine  tail.  It  consists  of  two  steel 
arms  and  a  wood  transverse  member  a  foot  wide.  On  this  flat  board, 
5  feet  7  inches  in  length  by  1  foot  wide,  and  J  inch  thick,  the  machine 
is  expected  to  fly,  or  rather  travel.  When  the  speed  is  sufficient — 


338 


-TYPES   OF   AEROPLANES  143 

and  the  machine  is  expected  to  attain  a  rate  of  65  to  70  miles  an  hour 
—the  plane  is  designed  to  lift  the  hull  out  of  water  entirely,  only  the 
wood  and  steel  tail  touching  at  intervals  to  steady  the  flight.  A 
powerful  eight-cylinder,  V-type,  water-cooled  motor  drives  a  6-foot 
two-bladed  wood  propeller  through  a  chain.  At  the  rear  of  the  hull  is 
placed  a  cane  seat  with  a  high  back,  the  cockpit  being  directly  in 
front  of  it.  The  control  levers  are  mounted  at  either  side.  Complete, 
the  machine  weighs  only  750  pounds.  The  first  model  made  65  miles 
an  hour  over  the  ice  of  Lake  Michigan,  scarcely  touching  the  surface, 
although  equipped  with  a  much  smaller  motor.  Though  having 
every  appearance  of  being  a  marine  aeroplane,  the  machine  is  really 
more  a  hydroplane  equipped  with  wings. 

Transatlantic  Hydroaeroplane.  As  the  result  of  his  long- 
continued  and  successful  experiments  with  the  hydroaeroplane, 
Glenn  H.  Curtiss  who  believes  that  the  crossing  of  the  Atlantic  in 
one  of  these  machines  would  be  quite  possible  is  ready  to  build  a 
special  aeroplane  for  the  purpose,  and  Roger  K.  Wallace,  chairman 
of  the  Royal  Aero  Club,  London,  is  making  efforts  to  raise  £20,000 
($100,000)  as  a  prize  for  the  first  America-to-England  flight.  H.  X. 
Atwood,  who  made  the  first  long-distance,  cross-country  flight  in 
America — St.  Louis  to  Boston — in  1911,  has  seriously  proposed  the 
undertaking,  as  has  also  James  V.  Martin,  who  is  a  master  mariner, 
as  well  as  a  licensed  aviation  pilot.  Mr.  Martin  gives  the  following 
data  regarding  the  trip: 

The  two  chief  difficulties  are  the  carrying  of  sufficient  fuel  for 
the  2,000-mile  flight,  and  the  question  of  navigation;  the  latter  is 
more  serious  than  it  may  at  first  appear  as  no  great  error  would  be 
necessary  to  divert  the  aeroplane  from  its  course  to  such  an  extent 
as  to  largely  increase  the  distance  and  risk  a  shortage  of  fuel.  On 
this  point,  Prof.  R.  W.  Willson,  of  Harvard,  who  has  made  a  life 
study  of  the  problems  of  nautical  astronomy  and  aerial  navigation, 
is  authority  for  the  following: 

Given  an  engine  which  can  be  absolutely  relied  on,  a  properly  con- 
structed aeroplane,  and  favorable  weather,  I  see  no  reason  why  the  trans- 
atlantic passage  of  less  than  2,000  miles  might  not  be  successfully  made. 
Assuming  that  the  mechanical  difficulties  of  keeping  the  aeroplane  in  motion 
can  be  successfully  overcome,  the  navigating  officer  would  first  have  to  select 
the  course  to  be  followed,  and  by  taking  the  ocean  steamship  "lane,"  the 
chances  of  loss  in  case  of  disaster  would  be  materially  lessened.  The  distance 


339 


144 


TYPES   OF   AEROPLANES 


from  Newfoundland  to  England  is  the  minimum.  But  the  problem  of  navi- 
gating an  aeroplane  is  a  peculiar  one.  The  path  of  a  ship  through  the  water 
is  determined  with  considerable  accuracy  by  the  course  and  distance  sailed 
as  determined  by  the  compass  and  the  log,  while  astronomical  observations 
are  used  to  check  this  "dead  reckoning"  at  stated  intervals,  unless  prevented 
by  clouds  or  fog.  The  aeroplane,  on  the  contrary,  may  often  be  at  a  sufficient 
altitude  to  allow  of  an  accurate  determination  of  its  position  by  observation, 
when  a  low-lying  fog  would  cut  off  from  a  ship  below  the  sight  of  the  horizon 
necessary  for  the  usual  observation  of  the  sun's  altitude.  The  difficulty  with 
the  aeroplane  is  to  keep  account  of  its  speed  and  its  direction  of  motion,  which 
is,  of  course,  more  dependent  on  the  motion  of  the  body  of  air  in  which  it  flies 
than  the  course  of  the  ship  is  dependent  on  the  ocean  current  or  its  leeway 
caused  by  the  wind  and  sea.  Since  there  is  no  treatise  published  on  the  sub- 


Fig.  63.     Device  for  Determining  Direction  and  Speed  of  an  Aeroplane  in  Flight 

ject,  I  would  venture  the  following  suggestions,  which  should  naturally  be 
thoroughly  tested  on  the  preliminary  trials  that  should  certainly  precede  any 
well-advised  attempt  to  make  the  journey. 

In  the  first  place,  it  should  be  definitely  ascertained  if,  in  good  weather, 
the  sea  horizon  is  sufficiently  defined  for  sextant  observations  at  the  height 
at  which  the  passage  would  be  made,  remembering,  of  course,  that  the  height 
could  be  decreased,  if  desired,  merely  for  the  purpose  of  making  observations. 
On  the  occasions  on  which  I  have  had  an  opportunity  to  observe  the  horizon 
at  elevations  of  2,000  to  5,000  feet,  the  uncertainty  has  been  so  great  that  I 
should  estimate  the  error  at  20  miles.  Special  refraction  tables  might  be 
necessary  at  the  height  of  a  mile,  though  it  is  true  that  an  uncertainty  of  20 
miles  is  of  far  less  importance  to  the  airman  than  to  the  seaman,  and  that  his 
problem  of  a  land  fall  is  in  some  respects  simpler.  There  should  be  no  diffi- 


340 


TYPES   OF   AEROPLANES  145 

culty  in  making  observations  of  the  altitudes  of  the  heavenly  bodies  if  the 
development  of  the  science  of  aviation  makes  it  necessary.  For  determining 
the  course  and  distance,  it  would  be  possible  to  learn  something  at  any  time 
when  the  aeroplane  could  be  made  to  pass  nearly  over  some  well-marked 
point  in  the  water  beneath — how  conspicuous  such  objects  would  have  to  be 
and  how  frequently  they  would  be  visible  is  uncertain.  Patches  and  streaks 
of  smooth  water  and  perhaps  other  objects  easily  visible  at  a  mile  or  two 
away,  and  sufficiently  stationary  to  be  used  from  a  rapidly  moving  aeroplane 
for  the  observations  of  a  four-point  bearing,  are  not  uncommon.  By  observing 
the  time  when  the  object  D,  Fig.  63,  is  directly  beneath  and  again  when  it 
is  left  behind  and  depressed  45  degrees  below  the  horizon,  the  distance  trav- 
eled in  the  observed  interval  of  time  is  equal  to  the  height  of  the  aeroplane, 
hence  the  speed  may  be  determined  while  a  compass  bearing  of  the  object 
taken  at  the  same  observation  gives  the  course.  Of  course,  all  the  methods 
of  using  two  bearings  and  the  elapsed  time,  which  are  useful  at  sea,  may  be 
modified  in  a  similar  way,  the  problem  being  the  reverse  of  the  nautical,  the 
distance  of  the  aeroplane  from  the  water  being  used  to  find  the  speed,  instead 
of  the  speed  being  used  to  find  an  unknown  distance.  Of  course,  it  is  neces- 
sary to  know  the  height  and  for  this  purpose  a  reliable  barometer  should  be 
carried,  and  it  has  been  suggested  that  the  often  unreliable  aneroid  be  checked 
by  finding  the  dip  of  the  horizon  and  then  computing  the  height;  this  would 
be  possible  with  a  fair  degree  of  accuracy  at  moderate  heights  and  with  a  clear 
horizon  by  means  of  the  navigator's  prism.  As  proposed  by  Vaniman,  the 
white  caps  can  be  employed  as  points  of  observation,  while  a  steamer  might 
also  serve  for  this  purpose,  by  making  allowance  for  its  speed.  Doubtless, 
a  method  that  would  prove  of  great  assistance  involves  no  observations  at 
all:  This  would  be  simply  to  obtain  "positions"  by  wireless  from  passing 
steamers,  and  there  are  so  many  of  the  latter  in  the  transatlantic  lane  that 
communication  would  always  be  easy.  To  ascertain  direction  and  speed,  a 
light  line  N  with  a  float  might  be  trailed  in  the  water,  and  it  is  probable  that  only 
a  very  small  float  would  be  necessary,  the  large  amount  of  line  dragging  fur- 
nishing the  necessary  friction.  If  the  direction  and  force  of  the  wind  were 
constant  at  all  levels  from  the  aeroplane  to  the  water's  surface,  or  if  condi- 
tions were  such  th^t  all  points  of  the  line  lay  in  the  same  plane,  this  plane 
would  indicate  pretty  accurately  the  direction  of  flight,  while  conditions 
could  be  so  arranged  that  the  vertical  angle  at  which  the  line  left  the  aeroplane 
would  give  a  measure  of  the  speed.  The  latter  might  also  be  ascertained  by 
the  use  of  a  small  patent  log  at  the  end  of  a  line,  or  by  measuring  the  compara- 
tive tension  of  a  spring  inserted  in  the  line  where  it  left  the  aeroplane,  as  shown 
at  E,  Fig.  63.  This  line  would  be  about  2  miles  long  and  the  aeroplane 
would  be  maintained  at  a  height  of  3,000  feet  during  the  observation. 

Probable  Features  of  Design.  The  special  difficulty  in  such  an 
extended  trip  by  aeroplane  is  that  of  sustaining  the  weight  of  oil 
and  fuel  necessary  to  keep  the  engines  running  during  the  period 
required  for  the  aeroplane  to  travel  from  St.  Johns,  Newfoundland, 
to  the  coast  of  Ireland,  a  distance  of  approximately  1,800  miles. 
Opinion  varies  as  to  the  type  of  machine  best  adapted  to  make 


341 


146 


TYPES   OF   AEROPLANES 


such  a  trip,  some  believing  that  extreme  speed  should  be  the  chief 
consideration  in  the  design,  since  a  speedy  machine  would  lessen  the 
time  and  require  less  fuel  on  that  account.  Others  believe  that  a 
slow,  large-surface  machine  would  be  more  reliable,  since  it  would 
carry  more  weight  per  horse-power  than  the  fast  machine.  Doubtless, 
a  design  between  these  two  extremes  would  lend  itself  best  to  the 
purpose,  that  is,  a  machine  sufficiently  powerful,  relative  to  its  area, 
to  have  a  speed  of  50  miles  per  hour  in  order  to  afford  control  in  gusty 
winds.  In  attempting  to  increase  the  speed  beyond  this,  the  resist- 


PA33AGE 
MOTO/?j         MOTORj 


COC/f  P/T 


Fig.  G4.      Design  of  Transatlantic  Hydroaeroplane 

ance  increases  so  disproportionately  that  a  very  substantial  increase 
in  the  size  and  weight  of  every  part  of  the  aeroplane  would  be  neces- 
sary. On  the  other  hand,  a  large  surface  machine  may  be  relatively 
inefficient  by  reason  of  its  slowness  and  very  dangerous  on  account 
of  its  sluggishness  in  control.  The  machine  proposed  is  a  biplane 
with  a  span  of  100  feet  by  a  chord  of  10  feet,  or  an  aspect  ratio  of  10 
to  1,  and  it  could  be  propelled  by  five  50-horse-power  revolving 
motors,  geared  down  ,to  two  tractor  screws.  This  would  give  it  a 
speed  of  50  miles  an  hour  and  a  weight-carrying  capacity  of  7,500 
pounds,  4,500  pounds  of  which  would  be  useful  load,  an  allowance 
that  would  provide  for  the  carrying  of  two  pilots,  one  engineer,  and 


342 


TYPES   OF   AEROPLANES  147 

sufficient  fuel  and  oil  to  drive  the  aeroplane  at  50  miles  per  hour  for 
36  hours.  Each  of  the  engines  would  be  fitted  with  a  friction  clutch, 
enabling  it  to  be  cut  out  at  any  time  for  inspection  or  adjustment. 
All  five  motors  would  be  used  to  attain  the  necessary  altitude  and 
speed  with  full  load,  but  as  the  fuel  was  consumed  and  the  machine 
lightened,  one  after  the  other  could  be  stopped,  thus  utilizing  the  fuel 
and  oil  to  the  greatest  advantage.  It  might  be  possible  to  sustain 
the  machine  with  only  two  of  the  motors  running  after  most  of  the 
fuel  and  oil  had  been  consumed. 

The  sketch,  Fig.  64,  shows  a  portion  of  the  enclosed  fuselage 
which  is  directly  under  the  normal  center  of  pressure.  Sufficient 
fuel  and  oil  could  be  stored  here  in  tanks  so  arranged  as  to  leave  a 
2-foot  passage  fore  and  aft  from  the  cabin,  just  under  the  pilot's 
cockpit,  to  the  engine  room.  The  extreme  width  of  the  fuselage  is 
8  feet  and  it  affords  6  feet  clear  headroom,  the  Engines  being  placed 
on  both  sides  of  the  enclosed  central  passage,  making  every  one  of 
them  accessible.  They  would  all  be  working  in  free  air  and  would 
drive  to  a  central  transmission  shaft,  from  which  the  tractor  screws 
are  driven  by  encased  silent  chains.  The  clutches  would  permit  of 
throwing  any  one  of  the  engines  in  or  out  of  operation  at  will,  so  that 
the  cleaning  of  the  valves  and  spark  plugs  should  be  as  simple  a 
matter  during  the  passage  as  at  rest,  though  for  that  matter,  experi- 
ence has  shown  that  a  36-hour  run  of  a  Gnome  revolving  motor  that 
is  clean  and  otherwise  in  good  condition  does  not  involve  any  par- 
ticular need  for  inspection  or  adjustment.  In  a  machine  as  large  as 
that  proposed,  the,  passage  fore  and  aft  of  the  engine  attendant  would 
hardly  be  perceptible  to  the  control  of  the  operator.  The  resistance 
of  such  a  machine  should  be  quite  low,  since  it  has  an  enclosed  stream- 
line form  throughout  and  since  the  single  row  of  struts  in  the  normal 
center  of  pressure  of  the  planes  greatly  reduces  the  wire  and  strut 
resistance  common  to  most  biplanes.  Though  large,  the  controls 
are  all  of  the  balanced  type,  so  there  would  be  no  difficulty  in  their 
handling  by  one  man  in  gusty  winds.  Two  boats  would  be  employed 
as  floats,  the  flat-bottom  hydroplane  principle  being  superfluous 
where  the  aeroplane  has  excess  lifting  capacity  to  raise  them  from 
the  water.  While  light,  these  would  be  made  so  as  to  serve  as  life- 
boats in  case  of  emergency.  If  it  became  necessary  to  alight  on  the 
water  in  midocean,  this  could  be  accomplished  in  a  comparatively 


343 


148  TYPES   OF   AEROPLANES 

smooth  sea  without  great  risk,  and  unless  the  seas  were  new  and 
short,  the  aeroplane  could  take  to  the  air  again  with  little  trouble. 
It  is  practically  certain  that  were  this  aeroplane  to  travel  at 
its  normal  speed  in  the  right  direction  for  30  hours  at  an  altitude  of 
about  5,000  feet,  the  passage  of  the  Atlantic  would  be  accomplished. 
A  height  of  5,000  feet  would  furnish  an  atmosphere  comparatively 
free  from  the  gusty  surface  winds  and  clear  of  all  fog,  so  that,  with  a 
polaris  instrument  and  a  special  azimuth  table,  it  would  not  be  neces- 
sary to  depend  on  the  compass  for  direction.  This  height  would  also 
give  a  greatly  extended  horizon  (80-mile  radius  at  4,900  feet)  so  that 
there  would  hardly  be  a  time  on  the  passage  over  on  the  steamship 
route  to  Europe  when  some  vessel  would  not  be  within  the  160-mile 
range  of  vision.  Noting  the  course  followed  by  these  vessels  would 
also  afford  a  check  on  the  other  methods  of  navigation  employed. 
A  glance  at  the  pilot  chart  of  the  North  Atlantic  for  July  and  August 
shows  that  there  is  a  very  dependable  westerly  movement  of  the 
upper  air  currents,  so  that  it  would  be  possible  to  rely  upon  a  greatly 
increased  speed  of  the  aeroplane  due  solely  to  the  wind. 


344 


VIEW    OF    THE    R.    E.    P.    MOTOR    AND    LANDING    GEAR 

This  Machine  is  the  Work  of  One  of  the  Cleverest  Aeroplane  Designers  in  Europe, 


AERONAUTICAL  MOTOR 


Early  Types.  In  the  general  acclaim  that  has  greeted  man's 
final  conquest  of  the  air,  the  chief  contributing  factor  that  has  made 
it  possible  has  to  a  great  extent  been  overlooked.  Power  in  suf- 
ficiently concentrated  form  appears  to  have  been  the  only  thing 
lacking  for  at  least  half  a  century  past  to  have  made  possible  for 
two  or  three  generations  what  has  been  the  reality  of  less  than  a 
decade.  Not  that  a  perfected  light-weight  power  unit  was  sufficient 
in  itself,  as  there  are  numerous  principles  governing  flight  that 
have  been  discovered  only  in  recent  years,  but  it  was  the  one  thing 
needed  to  lift  a  heavier-than-air  machine  from  the  ground  and  to 
keep  it  in  the  air.  With  its  aid,  it  appears  to  be  more  than  probable 
that  the  problem  of  the  sustaining  plane  and  the  difficulties  of 
equilibrium  would  have  found  a  solution  at  a  much  earlier  date. 
That  at  least  one  far-sighted  investigator  had  realized  the  possi- 
bilities of  the  monoplane  is  shown  by  Henson's  machine  of  1843. 
Henson's  steam  engine  was  justly  considered  a  marvel  for  its  antici- 
pated numerous  features  that  are  generally  considered  as  the  develop- 
ment of  but  very  recent  years  in  this  form  of  prime  mover. 

But  despite  the  great  improvements  it  embodied  and  the  fact 
that  it  could  be  operated  continuously  on  but  20  gallons  of  water, 
its  output  was  but  20  horse-power  for  a  total  weight  of  600  pounds. 
Compare  this  low  limit  of  30  pounds  per  horse-power,  of  sixty  years 
ago,  with  the  1.75  pounds  per  horse-power  of  the  140-horse-power 
Gnome  motor  and  the  advance  that  has  been  achieved  will  be  appre- 
ciated. "Continuously"  in  this  connection  meant  just  what  it  does 
today — as  long  as  the  fuel  holds  out — and  as  coal  is  not  only  exces- 
sively heavy  but  likewise  very  inefficient  for  its  weight  when  burned 
under  a  boiler,  as  compared  with  gasoline  used  directly  in  an  internal 
combustion  motor,  it  is  evident  that  even  with  the  great  supporting 
power  afforded  by  the  4,500  square  feet  of  surface  of  the  main  planes, 
Henson's  craft  could  not  have  carried  sufficient  coal  to  permit  of 
much  of  a  flight. 

Copyright,  1912,  by  American  School  of  Correspondence. 


345 


2  AERONAUTICAL   MOTOR 

That  extremely  light  weight  was  not  the  only  desideratum 
is  shown  by  Maxim's  engine  of  1892,  which  totaled  only  600  pounds 
for  an  output  of  more  than  360  horse-power,  or  actually  less  than 
2  pounds  per  horse-power  by  an  ample  margin.  The  boiler  weighed 
in  the  neighborhood  of  1,800  pounds.  The  engines  were  compound 
and  by  an  ingenious  regulating  device  the  high-pressure  steam  passed 
direct  to  the  low-pressure  cylinders  when  the  boiler  pressure  exceeded 
300  pounds  per  square  inch,  for  which  it  was  designed.  This  increased 
the  output  to  400  horse-power,  the  piston  speed  being  750  feet  per 
minute,  or  more  than  a  third  less  than  what  is  now  common  prac- 
tice with  the  internal  combustion  motor.  While  Maxim's  engine, 
boiler  plant,  and  equipment  were  extremely  light  for  the  power 
output,  they  had  to  work  under  the  great  disadvantage  inseparable 
from  the  use  of  steam — that  is,  the  low  thermal  efficiency  of  burn- 
ing fuel  under  a  boiler  and  the  consequently  increased  amount  that 
has  to  be  carried.  While  ample  sustaining  area  had  been  provided 
for  this  and  similar  purposes  (4,500  square  feet)  the  weight  of  the 
fuel  necessary  for  a  comparatively  short  flight  would  easily  have 
exceeded  that  of  the  entire  power  plant.  Apart  from  this  the  space 
required  for  the  machinery  was  out  of  all  proportion  to  the  total 
space  available,  particularly  as  it  would  have  been  more  or  less  essen- 
tial to  be  able  to  get  at  the  various  parts  of  the  plant  during  a  flight. 

In  this  case,  the  saving  in  weight  was  accomplished  only  at 
the  expense  of  other  disadvantages  that  would  have  rendered  the 
final  result  immature  had  the  machine  been  developed  to  a  point 
where  it  could  be  actually  employed  in  flight.  But  in  looking  back 
over  the  history  of  attempts  at  power-driven  airships,  it  will  be 
apparent  that  weight  has  been  by  far  the  greatest  deterrent  to 
success.  For  instance,  Giffard's  steam  engine  and  boiler  employed 
for  driving  a  dirigible,  in  1852,  weighed  350  pounds,  including  coal 
and  water,  for  an  output  of  3  horse-power.  Dupuy  De  Lome's 
dirigible  of  about  twenty  years  later  was  a  step  backward  in  this 
respect,  in  that  human  power  was  employed.  This  meant  a  weight 
of  close  to  2,000  pounds  per  horse-power,  while  the  maximum  power 
would  naturally  be  available  only  for  short  periods.  The  Tissandier 
electric  power  plant  of  1882  had  inherent  limitations  of  so  serious  a 
nature  where  weight  and  restricted  traveling  radius  were  concerned 
that  it  can  scarcely  be  considered  as  more  than  a  freak.  No  one 


346 


AERONAUTICAL   MOTOR  3 

conversant  with  the  drawbacks  inseparable  from  electric  power 
for  this  purpose  would  have  made  the  attempt.  The  If -horse-power 
motor  and  its  battery  of  primary  cells  weighed  500  pounds  and 
the  type  employed  (bichromate  cells)  was  such  that  the  power  was 
available  only  for  a  very  limited  period.  Despite  these  disadvantages 
the  first  dirigible  to  attain  any  measure  of  success  was  driven  by 
electricity.  This  was  the  La  France  of  18S4,  equipped  with  an 
8-horse-power  motor,  which  has  been  referred  to  already  in  the  earlier 
part  of  the  work. 

To  Santos-Dumont  doubtless  belongs  the  credit  of  being  the 
first  to  realize  the  great  possibilities  of  the  gasoline  motor  for  aerial 
navigation.  How  he  derived  his  inspiration  from  the  motorcycle 
engine  and  the  numerous  attempts  he  made  with  dirigibles  have 
already  been  dwelt  upon.  His  first  motor  weighed  between  15  and 
20  pounds  to  the  horse-power  and,  like  everything  he  has  been 
responsible  for  in  connection  with  aeronautics,  was  designed  on  a 
very  small  scale,  its  total  output  not  exceeding  4  horse-power. 
Although  a  pioneer  in  the  field,  Santos-Dumont  has  not  been  respon- 
sible for  the  subsequent  development  of  the  gasoline  motor.  At 
the  time  he  took  it  up,  the  first  stages  of  its  evolution  for  automobile 
propulsion  were  being  passed  through  and  the  difficulties  encoun- 
tered were  so  numerous  and,  in  many  instances,  of  such  a  puzzling 
nature,  that  it  is  easy  to  realize  why  attention  was  concentrated 
on  perfecting  it  for  a  purpose  that  did  not  involve  the  further  prob- 
lems of  successful  flight.  The  history  of  the  past  twenty  years  shows 
that  the  development  of  the  automobile  motor  was  no  small  task 
in  itself.  With  this  fairly  accomplished,  the  next  step  was  principally 
one  of  refinement  and  adaptation. 

GENERAL  MOTOR  REQUIREMENTS 

To  bring  about  its  required  refinement  and  adaptation  in  the 
aeronautic  motor  seems  a  comparatively  simple  matter,  but  that 
it  has  not  proven  so  in  fact  will  be  realized  upon  reviewing  the 
innumerable  expedients  that  have  been  adopted  by  different  builders 
to  meet  the  conditions,  and  the  many  departures  that  these  have 
involved  from  what  may  be  termed  automobile  practice.  In  fact, 
in  the  few  years  devoted  to  its  design,  practically  a  new  type  of 
motor  has  been  evolved.  In  order  to  obtain  a  clear  understanding 


347 


4  AERONAUTICAL   MOTOR 

of  how  this  has  been  brought  about,  it  is  first  necessary  to  realize 
how  exacting  the  requirements  are  and  of  just  what  they  consist. 
Following  this  with  a  study  of  some  of  the  more  representative  types 
that  are  now  built  for  aeronautical  use  will  reveal  how  the  various 
principles  laid  down  have  been  applied  in  each  case.  Before  taking 
this  up  in  detail,  it  may  make  matters  a  little  clearer  to  briefly  com- 
pare the  automobile  and  the  aeronautic  motor. 

Automobile  vs.  Aeronautical  Motor.  Generally  speaking,  the 
trend  of  the  past  few  years,  where  the  automobile  motor  is  concerned, 
has  been  to  develop  a  power  unit  of  more  unifprm  torque  and  of 
increased  efficiency.  The  more  general  adoption  of  the  six-cylinder 
motor  and  the  increase  in  the  length  of  the  stroke,  as  compared  with 
the  bore,  afford  evidence  of  this.  Little  or  no  attention  is  now  given 
to  the  question  of  weight  saving,  apart  from  any  reduction  that  the 
use  of  integrally  cast  inlet  manifolds,  more  direct  water  circulation, 
'  and  similar  efforts  at  cutting  down  the  length  of  piping,  may  have 
been  responsible  for.  Weights  have  reached  a  point  where  any 
substantial  reduction  could  be  brought  about  only  by  a  more  or 
less  radical  change  in  methods  of  construction,  as  well  as  the  use  of 
much  more  expensive  materials.  There  would  be  little  to  warrant 
the  increased  cost  of  a  much  lighter  motor,  besides  which  it  would 
involve  the  use  of  a  higher  speed  to  develop  the  same  power  with 
less  weight.  More  important  than  any  of  these  considerations  is 
the  fact  that  reliability  suffers  as  the  weight  decreases. 

Consequently,  the  tendency  in  the  development  of  the  auto- 
mobile motor  during  the  past  few  years  has  been  mainly  along  the 
line  of  increased  efficiency  with  practically  no  regard  for  the  matter 
of  weight,  while  the  chief  aim  of  the  builder  of  aeronautical  motors 
has  been  to  get  the  latter  down  to  the  minimum.  But  that  weight 
saving  is  not  the  sole  governing  factor  in  the  design  of  a  successful 
motor  for  flying  is  amply  evidenced  by  the  fact  that  the  first  aero- 
plane ever  to  make  a  flight — that  of  the  Wright  Brothers — was 
equipped  with  a  comparatively  heavy  motor.  Nor  has  this  motor 
undergone  any  radical  changes  since  it  was  first  adopted  several 
years  ago.  Like  the  Wright  biplane  of  standard  type,  it  is  not  only 
heavier  but  develops  less  power  than  many  other  experimenters 
have  thought  necessary  for  the  purpose.  But  in  it  efficiency  and 
reliability  have  been  developed  to  a  high  degree  and  these  vastly 


348 


AERONAUTICAL   MOTOR  5 

important  qualities  are  very  largely  responsible  for  the  numerous 
successful  flights  and  for  the  high  standing  which  the  Wright  ma- 
chines enjoy  in  the  field  of  aviation. 

It  did  not  take  long,  however,  to  reach  a  point  in  the  develop- 
ment of  the  aeroplane  where  the  speed  of  40  miles  an  hour  of  which 
the  Wright  biplane  was  capable,  was  considered  slow.  The  demand 
was  accordingly  for  more  and  more  power — the  greater  the  driving 
force  available,  the  smaller  the  sustaining  surface  needed,  with  a 
consequent  reduction  in  the  wind  resistance.  To  meet  this  demand 
and  still  keep  the  weight  down,  every  imaginable  expedient  has 
been  resorted  to  by  designers. 

It  has  been  said  that  the  most  important  problem  in  the  design 
of  a  light  motor  is  the  correct  choice  of  type,  but  when  what  has 
already  been  accomplished  in  this  field  is  passed  in  review,  it  will  be 
found  that  there  are  aeronautical  motors  of  every  type  ever  tried 
on  the  automobile  and  many  for  which  the  latter  was  not  respon- 
sible. Not  all  of  them  are  successful,  of  course,  but  many  of  such 
widely  differing  types  have  attained  such  a  measure  of  success  that 
there  is  no  telling  what  the  advances  of  the  next  five  years  may  be. 

Fundamental  Features  of  Design.  Short  Stroke.  As  an  aero- 
nautical motor  of  small  bore  and  long  stroke  is  much  heavier  in  com- 
parison to  its  power  output  than  one  in  which  these  two  dimensions 
are  more  nearly  the  same,  design  in  this  field  has  naturally  gone 
back  to  automobile  standards  of  several  years  ago  when  it  was 
customary  to  build  what  are  known  as  square  motors,  i.  e.,  those  in 
which  the  bore  arid  stroke  are  the  same.  In  fact,  it  was  nothing 
unusual  for  the  bore  to  exceed  the  stroke.  The  advantages  of  a 
long  stroke  are  increased  efficiency  and  somewhat  smoother  running, 
the  greater  fuel  economy  and  reduced  vibration  compensating  for 
its  inferior  weight  efficiency  on  the  automobile.  The  majority  of 
aeronautical  motors  are  accordingly  of  the  short  stroke  type,  as  the 
weight  decreases  very  rapidly  with  a  reduction  in  the  length  of  the 
stroke.  This  was  strikingly  illustrated  in  the  case  of  a  large  motor 
built  for  the  Vanderbilt  Cup  race  a  few  years  ago.  Its  original 
dimensions  were  7-inch  bore  by  7-inch  stroke.  In  re-designing  this 
motor,  it  was  made  7  by  6  inches,  the  1-inch  reduction  in  the  stroke 
being  responsible  for  a  saving  of  almost  200  pounds.  The  short- 
stroke  motor  has  the  further  advantage  of  a  low  center  of  gravity. 


349 


6  '  AERONAUTICAL   MOTOR 

Cost  No  Object.  While  compelled  to  reconcile  numerous  con- 
flicting requirements,  such  as  that  of  maximum  reliability  with  the 
minimum  weight,  the  designer  of  the  aeronautical  motor  is  not 
hampered  so  much  by  questions  of  cost.  Consequently,  many 
refinements  of  construction  are  available  that  could  not  be  indulged 
in  on  the  automobile  motor.  For  instance,  pistons  are  finished  all 
over,  inside  and  outside,  and  in  some  cases,  the  cylinders  themselves 
are  machined  direct  from  a  bar  of  solid  steel  at  a  cost  many  times 
greater  than  that  of  casting  them  of  iron.  Pistons  in  some  cases  are 
made  of  steel  in  order  to  attain  the  minimum  thickness  of  wall, 
and  every  possible  opportunity  is  taken  advantage  of  to  reduce 
weight,  such  as  making  the  piston  extremely  short — even  shorter 
than  the  stroke  in  some  instances.  Pressed  steel  is  resorted  to  in 
the  making  of  the  connecting  rods,  or,  where  forgings  are  employed, 
they  are  simply  riddled  with  holes  to  get  rid  of  every  ounce  of  metal. 

Low  Weight  per  Horse-Power.  It  must  be  borne  in  mind  that, 
even  at  this  early  day,  there  are  radically  different  standards  among 
builders  of  aeroplanes.  Some  are  constructed  for  purely  sporting 
purposes.  There  are  racing  machines  and  touring  machines,  if  the 
latter  appellation  be  permissible.  In  the  case  of  the  former,  the 
motor  must  develop  a  great  amount  of  power  for  a  comparatively 
short  period.  The  fact  that  its  construction  is  not  particularly 
durable  makes  it  possible  to  practically  eliminate  the  question  of 
any  factor  of  safety  in  its  parts.  The  latter  are  shaved  down  to  the 
last  fraction  of  an  ounce  and  reliability  is  sacrificed  in  consequence, 
but  before  going  into  action  the  motor  will  be  tuned  up  to  its  highest 
pitch,  and  if  it  will  run  long  enough  to  cover  a  certain  distance,  that 
is  all  that  is  necessary. 

Even  aluminum  has  been  employed  for  cylinders  in  rare  instances, 
the  bearing  surface  for  the  piston  consisting  of  a  thin  cast-iron  bush- 
ing forced  into  the  aluminum  casting.  This  has  the  great  disad- 
vantage of  providing  an  aluminum  explosion  chamber  and  this 
metal  loses  its  strength  very  rapidly  as  the  temperature  increases 
above  a  certain  degree.  It  likewise  involves  the  most  expensive 
form  of  construction  in  that  harder  seats  must  also  be  employed  for 
the  valves,  aluminum  being  entirely  too  soft  for  this  purpose.  Alumi- 
num cylinder  heads  have  also  been  employed  with  cast-iron  or  steel 
cylinders,  but  considerable  trouble  has  been  experienced  with  them 


350 


AERONAUTICAL   MOTOR  7 

owing  to  the  great  difference  in  the  ratio  of  heat  expansion  between 
aluminum  and  cast  iron  or  steel.  Consequently,  aluminum  is  no 
longer  employed  for  such  important  parts.* 

In  addition  to  drilling  the  connecting  rods,  they  are  usually 
made  very  much  shorter  than  in  automobile  practice,  this  being 
as  low  as  1.5  to  1.75  times  the  length  of  the  stroke  in  motors  of  a 
type  which  are  inherently  v/ell  balanced  by  reason  of  their  design, 
such  as  the  six-cylinder  vertical  or  the  three-cylinder  radial.  It 
will  seldom  be  found  to  exceed  2  to  2.25  times  the  stroke,  the  evil 
of  increased  friction  of  the  piston  against  the  cylinder  walls  due  to 
the  greater  angularity  of  the  short  connecting  rod  being  partly  com- 
pensated for  by  offsetting  the  crank  shaft  with  respect  to  the  cylinder 
center.  By  this  means,  the  pressure  between  the  piston  and  cylinder 
wall  are  practically  equalized  on  the  compression  and  power  strokes. 
The  crank  shaft,  cam  shaft,  and  even  the  valve  lifters  are  drilled  to 
reduce  weight,  the  passages  thus  made  eliminating  every  bit  of 
unnecessary  material,  and  affording  convenient  means'of  lubrication. 

Automatically-Operated  Inlet  Valves.  In  this  connection,  a 
further  reversion  to  what  is  now  obsolete  in  the  automobile  motor 
is  to  be  considered.  This  is  the  employment  of  automatically- 
operated  inlet  valves.  In  view  of  the  fact  that  the  aeronautical 
motor  is  seldom  called  upon  in  service,  to  vary  its  speed  much,  the 
high  degree  of  flexibility  to  which  the  automobile  motor  has  been 
developed  is  of  no  particular  advantage  and  the  shortcomings  of 
the  automatic  type  of  valve  are  not  a  serious  drawback.  Probably 
no  better  instancy  of  the  employment  of  the  automatic  valve  could 
be  mentioned  than  the  Gnome  revolving-cylinder  motors. 

As  is  the  case  with  most  other  important  parts  of  the  aero- 
nautic motor,  experience  with  the  automobile  has  been  drawn  upon 


*In  general,  however,  aluminum  or  aluminum  alloys  have  been  used  wherever  it  is  pos- 
sible to  substitute  these  alloys  for  the  heavier  metals,  such  as  iron  or  steel.  The  attempt  to 
use  them  for  casting  the  cylinders  is  not  new,  but  aluminum  itself  is  not  suitable  and  difficulty 
has  been  found  in  making  a  proper  alloy.  But  within  the  past  year  (1911)  magnalium  has 
been  successfully  employed  for  this  purpose.  This  consists  of  pure  aluminum  with  a  slight 
percentage  of  the  metal  magnesium  and  the  resulting  alloy  is  not  only  denser  but  is  about  12? 
per  cent  lighter  than  No.  12  aluminum,  which  consists  of  93  per  cent  aluminum  and  7  per  cent 
copper,  and  has  a  specific  gravity  of  2.82.  Magnalium  accordingly  weighs  about  one  third  as 
much  as  cast  iron,  while  its  thermal  conductivity  is  seven  to  eight  times  greater,  which  greatly 
facilitates  the  cooling,  especially  of  air-cooled  engines.  Unlike  other  aluminum  alloys  that 
have  been  employed  for  cylinders,  tests  have  demonstrated  that  it  gives  better  service  than 
iron  under  the  same  conditions,  as  the  bore  of  a  magnalium  cylinder  takes  on  a  mirror  polish 
after  only  a  few  hours  running,  while  the  surface  becomes  very  hard,  as  has  been  shown  by  the 
piston  and  rings  of  a  poorly-bored  cylinder  becoming  scored  instead  of  the  cylinder  walls,  as 
would  usually  be  the  case.  Owing  to  its  greater  strength  as  well  as  reduced  weight,  it  is  also 
being  employed  for  crank  cases  and  other  motor  parts.  The  expense,  however,  would  be  pro- 
hibitive for  anything  but  an  aeronautical  motor. 


351 


8  AERONAUTICAL   MOTOR 

in  the  placing  of  the  valves.  The  high-speed  automobile  motor 
has  shown  that  the  most  advantageous  valve  arrangements  are 
those  in  which  the  valves  are  in  the  head,  and  the  so-called  De  Dion 
arrangement  in  which  the  valves  are  in  line  with  each  other.  The 
reasons  for  this  will  be  obvious  when  it  is  borne  in  mind  that  power 
is  obtainable  only  with  high  speed  where  the  valves  are  very  liberally 
proportioned  with  regard  to  the  cylinder  bore.  The  combined  inlet 
and  exhaust  valve,  as  developed  on  the  Franklin  air-cooled  motor, 
has  also  been  successfully  applied  to  the  aeronautic  motor.  Plac- 
ing the  valves  in  the  head  makes  possible  a  very  simple  form  of 
explosion  chamber  with  a  minimum  of  wall  surface,  with  conse- 
quently increased  thermal  efficiency  as  compared  with  a  form  of 
cylinder  head  involving  the  use  of  valve  pockets.  The  absence  of 
the  latter  prevents  the  retention  of  spent  gases,  which  gives  increased 
power  and  fuel  efficiency  by  reducing  the  tendency  to  premature 
ignition  and  by  the  use  of  higher  compression  pressures,  which  mean 
higher  temperatures.  The  importance  of  this  is  obvious  in  view  of 
the  close  weight  limitations,  and  it  is  accordingly  customary  to 
employ  higher  compression  pressures  and  speeds  than  in  the  auto- 
mobile motor.  Considerable  interest  at  present  attaches  to  the 
development  of  motors  with  rotary  valves,  or  sliding  sleeves  and 
ports  instead  of  valves,  as  in  the  Silent-Knight  motor.  So  far  little 
definite  progress  appears  to  have  been  made  with  the  adaptation  of 
this  type  of  motor  to  the  aeroplane,  but  numerous  attempts  are 
being  made  to  evolve  a  practical  form  of  rotary  valve.  The  Knight 
motor  itself  does  not  offer  any  advantages  of  either  simplicity  or  re- 
duced weight  so  that  the  solution  does  not  lie  in  that  direction. 
An  interesting  development  where  the  valves  are  concerned  is  found 
in  the  Adams-Farwell  rotary  motor  in  which  the  fuel  is  injected  di- 
rectly into  the  cylinder  so  that  only  one  valve  is  necessary  for  each 
cylinder,  and  this  can  accordingly  be  made  of  very  liberal  diameter. 
Standard  Forms.  The  foregoing  will  suffice  to  give  some  idea 
of  the  difference  in  design  and  requirements  between  the  aero- 
nautic and  the  automobile  motor,  as  well  as  those  features  of  the 
latter  which  have  been  found  advantageous  in  the  new  field.  But 
so  far,  merely  the  parts  themselves  have  been  touched  upon.  It  is 
in  their  assembly  that  the  greatest  divergence  between  the  two 
standards  is  found.  A  glance  over  the  numerous  types  that  are 


352 


AERONAUTICAL   MOTOR  9 

sufficiently  successful  to  remove  them  from  the  class  of  freaks,  or 
mere  proposed  forms  of  construction  that  have  not  yet  got  beyond 
the  paper  stage,  reveals  the  fact  that  every  form  of  automobile  motor 
that  has  ever  been  devised,  has  its  counterpart  among  the  new- 
comers, besides  many  which  were  never  thought  of  in  that  connec- 
tion. At  one  end  of  the  list,  there  is  the  single-cylinder,  air-cooled, 
motorcycle  engine  with  which  Santos-Dumont  made  his  first  attempts 
at  dirigible  propulsion,  and  at  the  other  the  highly  refined  and 
extremely  ingenious  fourteen-cylinder  revolving  Gnome  motor, 
and  the  sixteen-cylinder  V-shaped  Antoinette.  Between  these  two 
there  is  every  form  imaginable,  even  the  two-cylinder  horizontal 
opposed — that  hybrid  type  of  purely  American  origin  and  develop- 
ment, which  foreign  designers  have  always  affected  to  despise, 
now  being  built  by  some  French  makers. 

V-Form.  The  V-form,  or  90-degree  arrangement  in  which  each 
pair  of  cylinders  acts  upon  the  same  crank  pin  is  very  largely  em- 
ployed, both  the  Wright  Brothers  and  Curtiss  using  this  type  in 
their  more  powerful  machines.  This  arrangement  permits  of  using 
a  crank  shaft  of  practically  the  same  dimensions  as  a  four-cylinder 
motor  of  the  same  size  and  is  accordingly  a  great  saving  of  weight. 
It  also  makes  it  possible  to  actuate  all  the  valves  from  a  single  cam 
shaft,  placed  in  the  point  of  the  V.  From  this  arrangement,  develop- 
ments have  led  to  the  placing  of  three  cylinders  round  a  common 
crank  case  in  the  same  vertical  plane,  also  seven  cylinders,  three  in 
one  plane  and  four  in  another,  as  in  the  Esnault-Pelterie  motor. 
Motors  of  this  and  similar  arrangement  are  popularly  referred  to  as 
"fan"  and  "star"  types,  and  as  all  the  cylinders  act  on  the  same 
crank  pin,  and  the  valve  gear  is  reduced  to  its  very  simplest  form, 
the  saving  in  the  weight  of  the  crank  shaft  and  crank  case  thus 
effected  may  readily  be  appreciated.  When  first  attempted  such 
motors  did  not  give  much  promise  of  being  practical,  but  as  they 
have  proved  such  a  success  in  actual  use,  they  are  now  one  of  the 
most  popular  forms  of  light-weight  motors.  Their  chief  disadvan- 
tage lies  in  the  amount  of  space  occupied  in  the  direction  across  the 
cylinders,  making  them  awkward  for  use  in  a  dirigible  for  which  a 
specially  designed  basket  or  car  of  greater  weight  is  necessary. 

Revolving  Cylinder.  Of  even  less  promise  at  the  outset  was  the 
revolving-cylinder  motor,  in  spite  of  the  fact  that  this  type  had  been 


353 


10  AERONAUTICAL   MOTOR 

developed  to  a  high  degree  of  reliability  and  efficiency  in  the  Adams- 
Farwell  car.  In  addition  to  the  other  difficulties  of  design,  the  gyro- 
scopic effect  of  the  revolving  mass  had  to  be  taken  into  considera- 
tion. It  is  well  known  that  a  large  flywheel,  revolving  rapidly,  forcibly 
resists  any  attempt  to  change  its  plane  of  rotation,  advantage  hav- 
ing been  taken  of  this  principle  to  balance  a  mono-rail  car  on  its 
single  support,  and  to  keep  torpedo  boats  steady  in  a  seaway.  While 
the  revolving-cylinder  motor  dispenses  with  a  flywheel,  its  revolving 
mass  acts  in  the  same  role  and  plays  the  part  of  a  gyroscope.  Plac- 
ing the  latter  horizontally  would  tend  to  increase  the  stability  of 
an  aeroplane  without  appreciably  affecting  its  steering,  but  it  was 
thought  that  where  run  in  a  vertical  plane,  as  is  necessary  in  order 
to  obtain  direct  driving  of  the  propeller,  it  would  interfere  with 
rounding  curves  of  short  radius.  In  the  case  of  the  Bleriot  mono- 
planes with  a  revolving-cylinder  Gnome  motor  right  up  forward, 
this  does  not  appear  to  have  been  the  case. 

The  chief  advantage  of  this  form  of  motor  is  its  ability  to  dis- 
pense with  a  flywheel  of  any  kind  and  its  highly  efficient  air  cooling. 
The  latter  has  proved  effective  even  with  motors  of  comparatively 
large  size,  using  an  initial  compression  as  high  as  75  pounds  to  the 
square  inch.  One  thing  that  the  aeronautic  engine  designer  does 
not  have  to  contend  with  is  dust  and  grit,  so  that  in  some  instances 
all  provisions  for  excluding  it  have  been  omitted. 

Correspondingly  greater  difficulties  are  found,  however,  in  the 
very  important  essential  of  lubrication  and  in  the  disposition  of  the 
piping.  Special  means  have  to  be  resorted  to  in  order  to  insure  the 
oiling  of  every  moving  part,  particularly  where  centrifugal  force 
enters  to  complicate  the  problem,  as  in  the  revolving  cylinder  motor. 
The  lubricating  system  employed  on  the  most  representative  type 
of  the  latter — the  Gnome — is  very  effective  but  likewise  very  waste- 
ful, as  the  oil  is  merely  pumped  through  the  motor  and  out  into  the 
air.  But  even  in  the  V-  and  fan-shaped  motors,  where  the  cylinders 
stand  directly  over  a  crank  case,  as  on  an  automobile  motor,  splash 
lubrication  can  not  be  employed.  The  last  cylinders  in  the  direction 
of  the  motor's  rotation  would  receive  very  little  oil.  Fewer  difficul- 
ties are  encountered  with  the  lubrication  of  motors  having  their 
cylinders  placed  horizontally  and  provided  with  a  vertical  crank 
shaft,  as  in  the  case  of  the  Farcot  and  Clement  engines. 


354 


AERONAUTICAL   MOTOR  11 

The  problem  of  properly  arranging  the  piping  is  one  that  has 
led  to  numerous  ingenious  expedients,  such  as  the  employment  of 
independent  feed  pumps  for  each  cylinder  on  the  eight-  and  sixteen- 
cylinder  Antoinette,  instead  of  a  carbureter  and  the  usual  com- 
plicated inlet  manifold.  The  latter  is  even  more  cleverly  dispensed 
with  in  the  case  of  the  Gnome  revolving  motor,  in  which  the  mixture 
of  air  and  gas  is  led  through  the  hollow  stationary  crank  shaft,  the 
different  cylinders  receiving  their  supply  through  automatic  inlet 
valves  placed  in  the  heads  of  the  pistons.  Where  the  flying  machine 
is  concerned  the  question  of  piping  has  one  redeeming  feature  in 
that  it  is  permissible  to  exhaust  directly  into  the  air.  No  one  but 
the  pilot  of  the  aeroplane  is  inconvenienced  by  this,  but  the  roar  is 
such  that  it  is  quite  likely  a  muffler  will  be  a  feature  of  the  aero- 
plane motor  before  very  long.  On  the  dirigible,  it  would  naturally 
be  very  dangerous  to  permit  the  escape  of  the  exhaust  anywhere 
near  the  gas  bag,  and  accordingly  a  muffler  is  not  only  employed, 
but  in  some  cases  both  the  exhaust  and  the  muffler  are  water  cooled 
to  make  certain  of  reducing  the  temperature  of  the  exhaust  to  a  safe 
limit. 

Flywheel.  One  other  advantage  enjoyed  by  the  aeronautic 
motor  is  the  fact  that  it  is  possible  in  most  instances  either  to  dis- 
pense with  the  use  of  a  flywheel  altogether,  or  reduce  its  weight  to 
an  almost  negligible  factor.  But  just  as  early  investigators  in  the 
automobile  field  did  not  appreciate  the  full  value  of  a  heavy  flywheel, 
so  some  designers  of  aeronautic  motors  do  not  consider  it  as  important 
as  it  really  is,  in  view  of  the  particular  types  of  motors  they  employ. 
Naturally,  the  conditions  are  quite  different,  as  the  propeller,  though 
very  light,  is  of  large  diameter  and  where  directly  attached  to  the 
crank  shaft,  does  away  with  the  necessity  for  a  flywheel.  In  review- 
ing the  large  number  of  aeronautic  motors  now  on  the  market, 
which  is  done  more  in  detail  a  little  further  along,  all  shades  of 
opinion  will  be  found  represented  where  this  ordinarily  important 
essential  is  concerned.  They  range  from  the  conventional  cast- 
iron  flywheel  of  automobile  type  found  on  the  Wright  motor  to  a 
perforated-steel  stamping,  as  in  the  Vivinus,  or  none  at  all,  this 
being  the  case  even  on  two-cylinder,  horizontal-opposed  motors  in 
which  the  impulses  are  very  intermittent.  Examples  of  this  are 
found  in  the  Darracq  and  the  Deuthil-Chalmers,  both  of  French  make. 


355 


12  AERONAUTICAL   MOTOR 

Number  of  Cylinders  and  Weight  Saving.  Mention  has  already 
been  made  of  the  fact  that  there  is  a  great  diversity  of  opinion  among 
aeroplane  motor  designers  regarding  the  number  of  cylinders.  As 
the  weight  of  an  engine  may  be  roughly  divided  into  cylinders  and 
pistons  on  one  hand,  and  the  crank  case  and  crank  shaft  on  the  other, 
assuming  the  conventional  type  it  will  be  evident  that  the  number 
of  cylinders  has  a  direct  bearing  on  a  most  important  factor — that 
of  weight.  In  the  numerous  "spider"  types  of  motors — if  they  may 
be  so  called — those  in  which  the  cylinders  radiate  from  a  very  much 
abbreviated  crank  case  with  a  correspondingly  reduced  crank  shaft, 
this  proportion  naturally  does  not  hold  good.  There  are,  of  course, 
many  other  factors  to  be  considered  in  the  selection  of  the  proper 
number  of  cylinders  and  it  will  be  apparent  from  a  study  of  the 
examples  illustrated  and  described  that  designers  have  become 
very  largely  divided  into  three  general  classes:  Those  favoring  what 
may  be  termed  the  conventional  type,  through  its  familiarity  on 
the  automobile — that  is,  the  vertical  or  V-arrangement  of  cylinders; 
those  who  favor  variations  of  the  radial  arrangement;  and  those  who 
pin  their  faith  to  the  revolving  motor,  this  really  being  a  subdivision 
of  the  second  class. 

Assuming  a  constant  r.  p.  m.  rate,  both  the  power  output  and 
the  weight  of  a  cylinder  increase  as  the  product  of  D2L,  D  denoting 
the  diameter  of  cylinder,  L  the  length  of  stroke;  but  if  a  constant 
piston  speed  be  assumed,  such  as  the  standard  of  1,000  feet  per 
minute  adopted  by  the  Association  of  Licensed  Automobile  Manu- 
facturers, on  which  to  base  motor  ratings,  the  power,  only,  increases 
as  the  square,  while  the  weight  still  increases  as  the  product  of  D^L. 
For  moderate  powers,  the  actual  weight  of  the  cylinders  them- 
selves appears  to  be  but  little  influenced  by  their  number,  but  it 
will  be  obvious  that  with  any  substantial  increase  in  power,  the 
weight  of  a  smaller  number  of  comparatively  large  cylinders  should 
be  less  owing  to  the  difficulty  of  reducing  the  thickness  of  the  cylin- 
ders in  proportion  to  their  reduced  dimensions.  Experience  has 
also  shown  that  an  engine  with  a  few  large  cylinders  has  a  very 
much  higher  factor  of  reliability  and  is  easier  to  maintain,  than  one 
with  a  large  number  of  small  cylinders.  While  exceedingly  fast  time 
has  been  made  over  short  stretches  by  an  eight-cylinder  V-type 
automobile  motor — the  200-horse-power  Benz — the  fastest  time  in 


356 


AERONAUTICAL   MOTOR  13 

road  races  over  long  distances  has  thus  far  always  been  to  the  credit 
of  the  four-  or  six-cylinder  motor  of  conventional  design. 

In  addition  to  almost  eliminating  the  crank  case,  the  small 
multi-cylinder  radial  type  also  dispenses  with  the  flywheel.  This 
last,  of  course,  is  equally  true  of  any  motor  employing  six  or  more 
cylinders,  as  the  multi-cylinder  motor  has  the  great  advantage  of 
producing  a  much  more  even  turning  moment.  The  drive  is  not 
continuous  in  a  four-cylinder  motor  and,  theoretically,  it  will  not 
run  at  all  without  a  flywheel.  However,  as  the  motor  is  directly 
connected  to  the  propeller  in  the  majority  of  instances,  the  latter  is 
frequently  found  an  efficient  substitute.  The  more  uniform  torque 
of  the  motor  with  the  greater  number  of  cylinders  is  an  added  advan- 
tage in  not  imposing  such  severe  stresses  on  connections  as  is  the 
case  where  a  smaller  number  of  power  units  is  employed.  But  the 
question  of  reliability  enters  here  again,  and  as  there  is  always  the 
possibility  of  one  or  more  cylinders  of  the  multi-cylinder  motor 
ceasing  to  fire,  the  reversal  of  stresses  is  then  quite  as  great  as  with 
fewer  cylinders. 

Coming  back  to  the  question  of  weight  saving — and  at  the 
present  time  it  is  evident  that  this  is  the  chief  controlling  factor — 
let  us  see  what  are  the  steps  leading  up  to  the  extremely  light-weight 
modern  motor.  With  the  conventional  arrangement,  i.  e.,  cylinders 
vertically  in  a  row,  the  weight  of  the  crank  case  and  crank  shaft 
naturally  increase  in  proportion  to  the  cylinder  capacity.  By  plac- 
ing two  rows  of  cylinders  on  the  same  crank  case,  as  in  the  usual 
V-arrangement,  the  size  of  the  crank  case  and  crank  shaft  are  but 
slightly  larger  than  for  the  single  row  and  the  weight  is  cut  almost 
in  half.  With  eight  cylinders  at  90  degrees,  the  impulses  are  evenly 
spaced  throughout  the  revolution,  each  pair  of  opposite  cylinders 
being  connected  to  one  crank.  But  both  impulse  and  mechanical 
balance  are  obtainable  with  as  small  a  number  as  two  cylinders, 
where  the  latter  are  arranged  in  what  is  known  as  the  horizontal- 
opposed  motor.  The  cylinders  are  slightly  offset  on  opposite  sides 
of  a  very  short  crank  case  and  they  act  upon  oppositely-disposed 
cranks — in  other  words,  a  two-throw  crank  shaft  with  the  pins 
placed  180  degrees  apart.  This  gives  a  very  smooth  running  motor 
where  two  or  any  multiple  of  two  cylinders  are  employed. 

The  advantages  of  this  type  are  mentioned  at  greater  length 


357 


14 


AERONAUTICAL   MOTOR 


here  as  they  have  only  recently  received  that  measure  of  apprecia- 
tion which  they  deserve,  as  will  be  noted  later  in  the  successful 
motors  of  this  type  that  are  now  in  use.  While  the  crank  case  and 
crank  shaft  of  the  horizontal-opposed  motor  increase  in  proportion 
to  the  increase  in  cylinder  capacity,  as  compared  with  the  diagonal  or 
"spider"  motor,  the  impulses  are  more  even  and  the  balance  better 
than  in  the  latter  when  using  less  than  four  cylinders. 

In  order  to  give  the  student  a  clearer  idea  of  the  manner  in 
which  the  crank  case  and  crank  shaft  are  affected  by  the  arrange- 
ment  of   the   cylinders,   with   a 
corresponding   reduction   in   the 
weight,  the  accompanying  illus- 
trations may  be  referred  to.     In 
these   sketches  the  details  have 
been    intentionally    omitted    to 


Fig.  1.     Four-Cylinder  Vertical  Type 


Fig.  2.     V-Type  of  2. to  16  Cylinders 


prevent  confusion;  in  actual  practice,  the  space  between  the  open 
ends  of  the  cylinders  on  the  crank  case  would  be  very  much  less 
than  is  here  indicated.  Fig.  1  is  the  conventional  four-cylinder  ver- 
tical motor  as  employed  on  the  automobile.  In  this  case  the  crank 
case  must  necessarily  be  slightly  longer  than  that  of  the  combined 
length  of  all  the  cylinders.  The  first  step  away  from  this  is  the  V 
or  90-degree  arrangement,  as  shown  by  Fig.  2,  which  illustrates  the 
elevation  and  the  plan.  A  similarly  great  reduction  in  the  size  of 
the  crank  case  is  effected  by  the  horizontal-opposed  arrangement, 
Fig.  3.  Either  the  diagonal  or  opposed  arrangement  lends  itself 
readily  to  two,  four,  six,  eight,  ten,  or  more  cylinders,  motors  of 


358 


AERONAUTICAL   MOTOR 


15 


the  diagonal  type  being  built  with  as  many  as  sixteen   cylinders. 

The  first  step  away  from  this   type   is  what   has   previously  been 

referred  to  as  the  fan  or  radial 

arrangement  as  shown  by  Fig. 

4,  also  as  carried  further   by 

the  addition  of  an  extra  pair 

of  cylinders,  as  in  Fig.  5. 

This  type  naturally  does 
not  lend  itself  as  well  to  water 
cooling  as  the  first,  second,  and 
third  arrangements  illustrated, 
owing  to  the  necessity  of  pro- 
viding an  independent  jacket 
for  every  cylinder  with  the 
attendant  complication  in  the 
piping.  But  for  air  cooling  this 
type  is  ideal,  as  the  cylinders 
are  so  spaced  that  each  one  re- 
ceives an  equal  amount  of  air  and  none  can  radiate  its  heat  directly  to 
any  of  the  others.  The  question  of  water  versus  air  cooling  is  naturally 
again  to  the  fore  in  this  field,  but  under  very  different  conditions  for 
the  latter  than  where  the  automobile  is  concerned.  Whether  directly 


Fig.  3.     Horizontal-Opposed  Type 


Fig.  4.     Three-Cylinder  Fan  Type 


Fig.  5.     Five-Cylinder  Fan  Type 


connected  to  the  propeller  or  used  to  drive  the  latter  through  a 
transmission  system,  the  motor  itself  is  always  completely  exposed 
to  the  air  and  is  cooled  by  a  current  averaging  40  to  60  miles  an  hour, 
or  even  greater.  There  would  appear  to  be  no  possibility  of  ever 
working  an  air-cooled  motor  so  hard,  even  on  a  warm  summer  day, 


359 


16 


AERONAUTICAL   MOTOR 


as  to  cause  it  to  be  any  less  reliable  on  the  score  of  danger  of  over- 
heating, where  the  conditions  are  so  favorable.  On  the  other  hand, 
with  a  multi-cylinder  motor  of  the  radial  type,  the  complications  of 
the  piping  system  and  connections  would  be  a  source  of  danger  in 
themselves.  For  numerous  reasons,  none  of  which  appears  to  have 
the  slightest  bearing  on  its  efficiency  or  reliability  as  judged  from  a 
purely  engineering  viewpoint,  the  air-cooled  motor  has  a  rather 
limited  use  in  the  automobile  field. 

Where  the  aeroplane  is  concerned,  however,  weight  saving  is 
of  vital  importance  and  space  is  also  a  factor  which  must  be  closely 

considered.  The  designer  of  aero- 
plane motors  is  neither  hampered 
by  restriction  of  style  nor  by  a 
commercial  demand.  He  does  not 
have  to  cater  to  a  buying  public 
that  has  to  a  great  extent  conven- 
tionalized automobile  design,  by 
refusing  to  aid  the  manufacturer 
whose  designs  in  any  way  departed 
from  the  conventional.  It  accord- 
ingly seems  quite  probable  that 
the  question  of  air  cooling  will  be 
worked  out  on  the  aeroplane  motor 
from  a  purely  engineering  view- 
point. Even  where  the  cylinders 
of  a  radial  type  of  motor,  such  as 
that  shown  by  Fig.  5,  are  placed 
so  close  together  there  should  be  no 
difficulty  in  properly  cooling  them. 

A  modification  of  Fig.  4  is  illustrated  in  Fig.  6,  which  shows 
a  four-cylinder  radial  motor.  In  practice,  however,  four  is  not  a 
good  number  for  this  type,  as  the  impulses  can  not  be  evenly 
divided,  which  accounts  for  the  general  use  of  an  odd  number  of 
cylinders  in  a  radial  arrangement.  Such  a  motor  can  be  satisfac- 
torily balanced  where  the  cylinders  are  evenly  spaced  about  the 
circumference  of  the  crank  case,  as  all  the  connecting  rods  are 
attached  to  a  common  crank  pin,  and,  therefore,  form  one  revolving 
mass,  which  can  be  balanced  by  a  suitable  balance  weight.  But  as 


Fig.  G.      I^our-Cylinder  Star  Type 


360 


AERONAUTICAL   MOTOR 


17 


the  number  of  cylinders  increases,  the  difficulty  arises  of  attaching 
all  the  big  ends  of  the  connecting  rod  to  Vme  crank  pin,  without 
making  the  ends  of  the  connecting  rods  unusually  narrow  or  the  pin 
itself  over  long.  This  is  obviated  by  the  arrangement  shown  in  Fig. 
118,  one  connecting  rod,  the  upper  one  in  the  sketch,  being  formed 
with  a  disk  to  which  the  others  are  attached  by  means  of  bosses,  or 
short  pins. 

In  balance,  this  engine  is  naturally  superior  to  either  of  the 
arrangements  shown  in  Figs.  4  and  5.  In  the  case  of  Fig.  4, 
the  placing  of  all  the  cylinders  on  top  of  the  crank  case  makes  it 
impossible  to  divide  the  impulses  evenly,  and  this  motor  has  to  be 
built  with  heavy  inside  flywheels,  similar  to  a  motorcycle  engine. 
With  this  addition,  such  a 
motor  runs  well,  but  it  is  a 
question  whether  the  advan- 
tage of  greater  accessibility 
gained  by  placing  the  cylinders 
in  this  position,  is  not  more 
than  offset  by  the  extra  weight 
of  the  flywheels  that  could  be 
saved  by  disposing  the  cylin- 
ders equidistant  around  the 
crank  case,  so  that  the  im- 
pulses would  come  120  de- 
grees apart. 

Fig.    5    is    really   a  five-      Fig 
cylinder  radial  engine  with  the 

two  cylinders  shown  below  in  Fig.  7  placed  on  top  of  the  crank  case. 
In  this  case,  three  of  the  pistons  actuate  one  crank  and  the  remain- 
ing two  another,  the  cranks  themselves  being  opposed  or  180  degrees 
apart.  The  division  of  the  impulses  is  the  same  as  in  the  complete 
radial  engine,  Fig.  7,  and  the  balancing  almost  as  good,  but  the 
crank  shaft  has  to  be  of  a  larger  diameter  owing  to  its  weaker  form, 
and  as  both  it  and  the  crank  case  are  longer,  there  will  be  an  increase 
in  the  weight.  Take  Fig.  7  and  assume  that  its  crank  shaft  is 
held  stationary,  and  we  have  the  usual  revolving  type  of  radial 
motor  which  has  proven  so  successful  in  service.  It  does  not  require 
any  great  amount  of  study  to  show  that  whether  the  cylinders  revolve 


Five-Cylinder  Radial  or  Star  Type 


361 


18  AERONAUTICAL   MOTOR 

or  remain  stationary,  the  total  weight  of  the  motor  will  be  the  same, 
assuming  the  accessories  and  fittings  in  each  case  to  be  similar.  This 
being  the  case,  the  only  manner  in  which  the  revolving  cylinders 
can  be  of  any  advantage  is  either  to  make  the  crank  case  and  the 
cylinders  themselves  lighter,  or  to  obtain  more  power  for  the  same 
sized  cylinder  when  revolved. 

The  chief  advantages  of  the  revolving  motor  are  that  it  dis- 
penses with  a  flywheel  and  makes  air  cooling  more  positive.  Under 
the  conditions  obtaining  on  an  aeroplane  soaring  at  any  consider- 
able height,  it  may  be  questioned  whether  this  is  not  really  too  much 
so,  the  great  reduction  in  the  temperature  of  the  motor  very  unfavor- 
ably affecting  its  efficiency  and  unduly  increasing  its  fuel  consump- 
tion. That  this  is  quite  likely  to  be  the  case  will  be  apparent  from 
the  fact  that  in  a  revolving  motor  in  which  the  ends  of  the  cylinders 
are  15  inches  from  the  crank  shaft,  the  former  will  be  moving  through 
the  air  at  95  miles  an  hour  when  the  motor  is  running  at  1,200  r.  p.  m. 
In  practice,  the  power  obtained  per  cubic  inch  of  cylinder  capacity 
from  the  Gnome  motor  is  small,  and  it  seems  quite  probable  that 
the  same  power  could  be  obtained  by  employing  fixed  cylinders  of 
smaller  dimensions.  That  it  is  extremely  light  for  its  size  will  be 
seen  from  its  weight  of  but  0.35  pound  per  cubic  inch  of  cylinder 
capacity,  but  this  is  undoubtedly  due  to  the  high-grade  materials 
used  and  the  methods  of  machining  employed  in  its  construction. 

Another  point  of  importance  in  the  comparison  of  these  various 
arrangements  that  is  quite  as  vital  as  that  of  weight,  or  will  be  as 
soon  as  durability  in  an  aeroplane  motor  is  given  proper  considera- 
tion, is  their  effect  on  the  bearings.  By  grouping  the  cylinders  the 
crank  case  is  shortened  but  the  work  put  on  the  bearings  is  increased, 
without,  in  most  cases,  any  proportionate  increase  in  the  amount  of 
bearing  surface.  For  instance,  in  the  diagonal  or  V-type,  each  main 
bearing  has  to  take  the  load  of  two  cylinders,  instead  of  one.  This 
is  aggravated  still  further  by  placing  three  cylinders  on  top  of  the 
crank  case  and  in  the  radial  type  matters  are  still  worse,  though  in 
the  latter,  various  expedients  to  overcome  this,  such  as  that  illus- 
trated by  Fig.  7,  are  adopted. 

The  difficulty  of  lubricating  the  radial  type  of  engine  has  already 
been  mentioned  and  need  not  be  repeated  here.  Just  how  each  maker 
has  solved  this  extremely  important  part  of  the  problem  of  his  design, 


362 


AERONAUTICAL   MOTOR  19 

will  be  referred  to  in  connection  with  the  descriptions  of  a  number 
of  prominent  American  and  European  aeronautical  motors  that 
follow. 

AMERICAN  MOTOR  TYPES 

Wright.  As  the  Wright  motor  was  the  first  to  leave  the  ground 
in  a  man-controlled  aeroplane,  it  is  natural  that  it  should  be  given 
prominence  in  this  connection.  When  the  Wright  Brothers  attacked 
the  problem  of  using  power  for  their  flights  they  searched  the  mar- 
ket for  a  suitable  motor  but  were  unable  to  find  anything  that  met 
their  requirements.  It  will  be  recalled  that  the  automobile  motor 
was  not  a  very  highly  developed  power  unit  in  1902.  They  were 
accordingly  compelled  to  develop  a  design  by  study  and  experiment, 
as  in  the  case  of  the  aeroplane  and  the  propellers.  The  result  is  an 
exceedingly  simple  and  efficient  motor  of  the  four-cycle  type  which 
at  first  glance  resembles  the  present-day  automobile  motor  of  light 
cars,  particularly  since  the  practice  of  making  an  oil  tank  an  integral 
part  of  the  crank  case  has  come  into  vogue.  The  Wright  motor 
is  of  the  four-cycle  type,  the  cylinders  being  cast  independently 
of  gray  iron,  while  the  crank  case,  of  unusual  depth,  is  of  aluminum 
alloy,  as  are  also  the  water  jackets  of  the  cylinders.  The  exhaust 
valves  are  in  cages  opening  directly  to  the  air  and  are  operated  by 
means  of  rocker  arms,  as  they  are  placed  in  the  head,  alongside  of 
the  automatic  inlet  valves.  The  crank  shaft  is  of  nickel  steel  and 
in  accordance  with  the  practice  that  obtained  in  the  automobile 
field  seven  or  eight  years  ago,  it  is  whittled  out  of  a  solid  block,  the 
cam  shaft  also  being  machined  from  the  bar  in  the  same  manner. 
Oil  is  carried  in  a  special  tank  forming  the  bottom  of  the  1 -piece 
crank-case  casting,  lubrication  being  insured  by  a  small  gear  type 
of  pump  driven  from  the  cam  shaft.  A  second  small  gear  pump 
driven  in  the  same  manner  and  located  beside  the  oil  pump, 
shown  in  the  illustration  of  the  right  side  of  the  motor,  Fig.  8,  is 
for  the  purpose  of  supplying  the  fuel  to  the  engine,  a  carbureter 
being  dispensed  with  in  view  of  the  extreme  variations  of  altitude 
under  which  the  motor  must  operate.  As  will  be  apparent  from  the 
photo,  this  pump  delivers  the  gasoline  direct  to  a  mixing  chamber 
located  at  an  elbow  of  the  intake  manifold,  the  end  of  which  is  open 
to  the  air.  An  injector  controls  the  amount  of  gasoline  supplied  to 


363 


20 


AERONAUTICAL   MOTOR 


each  cylinder  in  direct  proportion  to  the  speed  of  the  engine.  By 
comparison  with  the  highly  developed  type  of  carbureter  now 
employed  on  the  automobile,  this  device  appears  to  be  a  reversion 
to  the  old  stationary  engine  type  of  mixer,  but  it  must  be  borne  in 
mind  that  an  aeroplane  motor  constantly  operates  at  its  normal 
or  even  maximum  output,  so  that  provision  which  would  be  totally 


Fig.  8.     Right  Side  of  Wright  Four-Cylinder  Aeronautical  Motor 

unsuited  to  automobile  use  in  view  of  the  demand  for  the  greatest 
possible  range  of  speed  and  power  output,  is  undoubtedly  far  more 
reliable  under  such  ideal  conditions  of  operation. 

Ignition  is  provided  by  a  "Mea"  high-tension  magneto  driven 
by  a  two  to  one  gear  on  the  end  of  the  cam  shaft  but  outside  of  the 
crank  case,  the  magneto  being  set  on  a  bed  cast  integral  with  the 
latter.  In  this  type  of  magneto,  the  entire  field  magnet  is  arranged 
to  oscillate  about  the  armature,  so  that  regardless  of  the  position  of 
"advance"  or  "retard"  for  which  the  spark  control  is  set,  the  spark 


364 


AERONAUTICAL   MOTOR  21 

always  occurs  at  what  is  known  as  the  "peak  of  the  curve,"  i.  e., 
the  point  of  greatest  current  flux,  giving  a  spark  of  the  maximum 
value  for  ignition  purposes.  The  cooling  water  is  circulated  by  means 
of  a  centrifugal  pump  attached  directly  to  the  end  of  the  crank 
shaft,  as  shown  by  the  view  of  the  left  side  of  the  motor,  Fig.  9, 
which  also  illustrates  the  magneto  and  its  drive.  The  radiator  con- 
sists of  a  small  group  of  flat,  vertical,  copper  tubes,  several  feet  in 


Fig.  9.     Left  Side  of  Wright  Four-Cylinder  Motor  Showing  Magneto  and  Its  Drive 

height,  and  with  small  aluminum  headers  at  each  end.  Unlike 
many  designers  of  aeronautic  motors,  the  Wright  Brothers  have  not 
attempted  to  reduce  weight  at  the  expense  of  safety,  as  will  be  very 
apparent  from  the  liberal  flywheel  provided.  Where  not  more  than 
four  cylinders  are  employed,  there  is  no  single  feature  that  adds 
so  greatly  to  the  reliability  of  a  motor  and  the  uniform  delivery  of 
its  power  output,  as  a  flywheel  of  ample  weight.  This  essential  is  of 
web  pattern  and  is  of  cast  iron,  instead  of  the  usual  spoked  wheel 
commonly  employed.  The  cylinder  dimensions  are  4f-inch  bore 


365 


22  AERONAUTICAL  MOTOR 

by  4-inch  stroke,  the  power  output  being  30  to  35  horse-power  at 
about  1,200  r.  p.  m.  The  total  weight,  not  including  the  radiator  or 
water  supply,  is  180  pounds,  or  5J  to  6  pounds  per  horse-power, 
which  is  very  high  as  compared  with  the  weights  of  the  majority  of 
aeronautic  motors.  The  power  is  transmitted  to  the  propellers 
through  the  two  sprockets  shown  on  the  crank  shaft  at  the  flywheel 
end,  and  nickel  steel  roller  chains,  one  of  the  latter  being  crossed  to 
reverse  the  motion  of  its  screw.  The  propeller  shafts  are  of  chrome 
nickel  steel  and  are  carried  on  annular  ball-bearings.  The  high 


Fig.  10.     Complete  Power  Plant  and  Transmission  of  Wright  "Baby"  Biplane 

degree  of  reliability  shown  by  the  Wright  motor  in  service  affords 
a  striking  illustration  of  the  fact  that  extremely  light  weight  is  far 
from  being  the  chief  thing  to  be  desired  in  an  aeroplane  motor. 
For  the  "baby"  Wright  machine  and  the  "racer,"  an  eight-cylinder, 
V-type  motor,  Fig.  10,  which  is  characterized  throughout  by  the 
same  features  of  design,  is  employed.  This  is  rated  at  60  horse-power, 
and  is  designed  to  drive  the  propellers  at  a  much  higher  rate  of  speed 
than  in  the  standard  machine  in  which  they  turn  at  400  r.  p.  m. 

Curtiss.  On  the  early  Curtiss  aeroplanes,  a  four-cylinder,  ver- 
tical, four-cycle,  air-cooled  motor,  which  was  practically  the  same 
in  most  respects  as  the  standard  automobile  type,  was  employed. 


366 


AERONAUTICAL  MOTOR 


23 


This  developed  about  25  horse-power.  It  soon  gave  way,  however, 
to  an  eight-cylinder,  V-type  motor  of  the  same  general  design  rated 
at  50  horse-power,  and  it  has  been  with  this  motor  that  Curtiss  has 
made  all  of  his  flights  of  note.  The  new  Curtiss  racer  is  provided 
with  a  water-cooled  motor,  Fig.  11,  something  which  serves  to 
accentuate  the  difference  in  the  conditions  between  land  and  a'ir 
travel.  It  would  appear  that  in  view  of  the  high  wind  blowing  on 
the  motor  and  the  low  temperature  of  the  air  blast,  that  air  cooling 


Fig.  111.     Curtiss  Water-Cooled  V-Type  Motor 

would  present  no  difficulties  whatever.  As  already  mentioned, 
however,  an  aeroplane  motor  operates  constantly  under  full-load 
conditions,  and  the  rear  cylinders  of  a  longitudinally-arranged  motor 
are  apt  to  become  overheated  despite  the  constant  supply  of  cold  air 
blowing  on  them.  This,  in  addition  to  involving  the  risk  of  stopping 
the  motor  without  warning,  also  cuts  down  the  power  of  these  cylin- 
ders due  to  the  rarefaction  of  the  fuel  mixture  at  a  high  temperature, 
makes  lubrication  difficult,  and  greatly  increases  the  consumption 
of  lubricating  oil.  Tabuteau's  8-hour  flight  in  France  with  a 
Renault  air-cooled  motor  shows  the  efficiency  of  air-blast  cooling. 
The  amazing  rapidity  with  which  aviation  has  progressed  dur- 


367 


24  AERONAUTICAL   MOTOR 

ing  the  past  few  years  has  been  responsible  for  the  entrance  of  a 
number  of  motor  manufacturers  into  the  field,  many  of  whom  are 
already  building  automobile  or  marine  motors,  while  others  under- 
took the  making  of  special  aeronautic  motors  from  the  start.  As  is 
naturally  to  be  expected,  the  majority  of  the  motors  turned  out 
by  the  former  class  are  more  or  less  conventional  in  their  design, 
though  distinguished  by  special  features  in  some  instances,  yet  not 
as  a  whole  of  sufficient  interest  to  merit  detailed  description  of  more 
than  a  few  that  may  be  regarded  as  representative  of  a  class. 

Four=Cylinder  Water=Cooled  Type.  The  first  of  these  is  the 
four-cylinder  four-cycle  vertical  water-cooled  motor.  This,  in 
brief,  is  nothing  more  nor  less  than  a  light  type  of  automobile  motor, 
and  in  some  cases  no  great  attempt  has  been  made  at  weight-saving, 
as  there  are  several  in  which  the  water  jackets  are  of  cast  iron,  in- 
tegral with  the  cylinders  as  in  automobile  practice. 

Harriman.  In  the  Harriman,  these  were  at  first  replaced  by 
copper  jackets  and  more  recently  by  light  sheet-steel  jackets  auto- 
genously  welded  in  place,  thus  insuring  against  leakage.  A  novel 
feature  of  this  motor  is  the  fact  that  the  lower  ends  of  the  cylinders 
are  threaded  and  screw  directly  into  the  crank  case  and  lock,  the 
usual  flange  and  bolt  fastening  being  done  away  with.  Both  valves 
are  placed  side  by  side  in  the  head  and  are  operated  by  a  super- 
imposed cam  shaft  placed  between  them  and  driven  by  a  vertical 
shaft  and  bevel  gears  from  the  crank  shaft.  The  same  cam  operates 
both  the  inlet  and  exhaust  valve  in  each  case.  The  water  jacket  of 
the  cylinder  head,  and  the  valve  ports  are  cast  with  the  cylinder, 
the  jacket  of  the  barrel  being  of  sheet  steel  as  mentioned.  An  auxiliary 
exhaust  port  in  the  form  of  a  series  of  holes  drilled  in  the  cylinder 
castings  and  uncovered  by  the  piston  at  the  lowest  point  of  its  stroke 
aids  in  quickly  scavenging  the  cylinders.  The  Harriman  is  one  of  the 
few  aviation  motors  on  which  the  option  of  battery  ignition  is  offered, 
the  Atwater-Kent  system  being  employed.  These  motors  are  built 
in  two  sizes,  30  and  50  horse-power  and  are  designed  to  run  at  1,400 
r.  p.  m.  Their  weight  is  four  pounds  per  horse-power. 

Horizontal=Opposed  Type.  On  one  hand  there  has  been  a 
demand  for  a  simpler  and  lighter  motor  to  give  the  same  power  as 
the  type  just  mentioned,  and  on  the  other  for  greatly  increased 
power.  The  former  has  been  met  by  the  horizontal-opposed  type. 


368 


AERONAUTICAL   MOTOR 


25 


Detroit  Aero.  An  example  of  this  is  the  Detroit  Aero,  which 
with  cylinders  of  5  J-inch  bore  by  5-inch  stroke  is  rated  25  to  30  horse- 
power at  1,500  r.  p.  m.  The  valves  are  located  in  the  head  and 
actuated  by  tappet  rods  and  rocker  arms.  Cooling  is  by  air  direct, 
the  arrangement  of  the  cylinders  lending  itself  with  great  advantage 
to  this.  Quite  a  number  of  this  type  of  motor  are  now  being  used 


Fig.  12.     Call  Aviation  Motor  Fitted  with  Mufflers 


in  France  where  they  were  never  regarded  favorably  for  automobile 
work. 

Call.  A  specially-designed  horizontal-opposed  type  is  the 
Call  aviation  engine,  Fig.  12.  This  has  four  cylinders  opposed  in 
two  pairs,  the  dimensions  being,  bore  6  inches,  stroke  5J  inches,  and 
rated  at  90  horse-power.  It  is  also  built  as  a  two-cylinder  opposed 
rated  at  45  horse-power.  The  cylinders  are  of  a  vanadium  alloy  iron, 
machined  inside  and  outside  and  pressed  into  magnalium  (a  very 
strong  and  light  aluminum  alloy)  water  jackets.  To  save  weight, 
the  cvlinders  are  cast  of  the  usual  thickness  at  the  combustion  cham- 


369 


26 


AERONAUTICAL   MOTOR 


her,  extending  down  as  far  as  the  stroke  of  the  piston,  and  from  there 
on  to  the  crank  case  are  only  half  as  thick.  It  is  claimed  that  this 
construction  in  connection  with  the  unusually  light  jackets  gives 
a  weight  per  horse-power  equal  to  that  for  the  cylinders  of  the 
customary  construction.  Ribs  extend  inwardly  from  the  magnalium 
jacket  and  press  tightly  against  the  machined  outer  surface  of  the 
cylinder,  thus  reinforcing  the  combustion  chamber.  The  cylinder 
heads  are  of  the  same  construction  as  the  cylinders,  the  main  portion 


Fig.  13.     65-Horse-Power  Indian  Aeromotor,  Hendee  Manufacturing  Company 

being  of  magnalium  which  is  lined  with  a  circular  plate  of  iron  over 
the  combustion  chamber.  Both  valves  are  mechanically  operated 
and  are  in  cages  in  the  head.  The  valve  seats  are  water  cooled  while 
the  cages  are  air  cooled  to  save  weight.  These  cages  are  cast  very 
thin  and  have  cooling  flanges  to  protect  the  valve  stem  bearings. 
The  pistons,  cast  of  the  same  iron  as  the  cylinders,  are  provided 
with  internal  cooling  flanges  on  the  heads.  Magnalium  is  also 
employed  for  casting  the  crank  case,  numerous  internal  ribs  amply 
reinforcing  it.  Lubrication  is  by  the  splash  system,  the  supply  being 


370 


AERONAUTICAL   MOTOR 


27 


maintained  by  individual  oilers  in  the  form  of  large  cups  on  the  tops 
of  the  cylinders.  A  quick  exhaust  is  insured  by  the  use  of  large 
valves  with  a  full  lift  of  approximately  one-fourth  the  valve  diameter, 
supplemented  by  auxiliary  exhaust  ports  at  the  end  of  the  stroke.^ 
The  Call  engine  is  the  first  aeronautical  motor  to  be  fitted  with  a 
muffler.  Silencers  of  special  design  without  the  usual  tubes  or  baffle 
plates  are  fitted  directly  to  the  exhaust  valves  and  auxiliary  exhaust 
ports  of  every  cylinder,  extending  straight  downward.  The  weight 
of  the  45-horse-power  motor  is  135  pounds,  and  of  the  90-horse-power 
type,  225  pounds,  or  3  and  2.5  pounds  per  horse-power,  respectively. 


Fig.  14.     Hamilton  Eight-Cylinder  V-Type  Motor 

Eight=Cylinder  V=Type.  Hendee.  The  Hendee  aviation  motor 
may  be  cited  as  an  example  of  the  eight-cylinder  V-type,  Fig.  13. 
No  attempt  has  been  made  to  achieve  extreme  lightness,  the  object 
being  rather  to  provide  a  motor  that  will  carry  full  load  for  long 
periods.  The  cylinders  and  heads  are  cast  separately,  the  former 
having  a  light  brass  water  jacket  spun  into  grooves  and  the  joint 
brazed.  The  heads  have  separate  jackets  connected  to  the  cylinder 
jackets  by  a  flexible  joint.  Both  valves  are  placed  in  an  out-board 
port  on  the  inner  sides  of  the  cylinders,  the  inlet  valve  being  placed 


371 


28  AERONAUTICAL   MOTOR 

on  top  and  operated  by  a  rocker  arm  while  the  exhaust  is  operated 
direct.  The  inlet  valve  is  carried  in  a  cage  held  in  place  by  a  breech- 
block lock;  its  removal  exposes  the  exhaust  valve  and  permits  its 
withdrawal.  The  cylinder  dimensions  are  4-inch  bore  by  4|-inch 
stroke,  the  output  being  60  to  65  horse-power,  and  the  weight  260 
pounds,  or  4.3  pounds  per  horse-power.  Curtiss  used  one  of  these 
motors  in  the  long-distance  flights  at  the  Harvard  Aviation  Meet. 

Hamilton.  The  Hamilton  motor,  Fig.  14,  is  of  the  conventional 
eight-cylinder  V-type,  but  is  distinguished  by  an  unusual  valve 
operating  mechanism  most  of  the  details  of  which  will  be  apparent 
from  the  photograph.  Both  valves  are  placed  in  the  cylinder  heads, 
and  the  entire  valve-operating  mechanism  is  superimposed  on  them. 
The  vertical  tube  visible  in  the  foreground  between  the  cylinders 
is  a  crank-case  "breather"  or  vent. 

Two=Cycle  Motors.  Roberts.  As  already  mentioned,  the  aero- 
plane affords  an  excellent  field  for  the  two-cycle  motor  in  view  of  the 
constant  power  requirements,  similar  to  the  condition  obtaining  in 
marine  wrork.  A  representative  motor  of  this  type  is  the  Roberts, 
designed  by  E.  W.  Roberts,  whose  experience  in  the  field  of  aviation 
dates  back  to  1894  and  1895  when  he  served  as  assistant  to  Hiram 
S.  Maxim  in  his  experiments  at  that  time.  The  Roberts  two-cycle 
aviation  motor  is  of  the  customary  three-port  type  except  that 
instead  of  opening  the  admission  and  exhaust  by  means  of  the  piston, 
a  special  tubular  rotary  valve  is  employed,  it  being  claimed  that 
this  effects  better  control  of  the  opening  to  the  crank  case  and  greater 
economy.  The  cellular  by-pass  fitted  to  Roberts  marine  motors 
is  also  employed  to  prevent  back  firing  or  explosions  in  the  crank 
case.  The  cylinders  are  of  hardened  steel,  their  dimensions  being 
4|-inch  bore  by  5-inch  stroke.  Part  of  the  water  jacket  is  cored  out 
of  the  cylinder  casting  while  the  remainder  is  covered  with  an  alumi- 
num jacket  caulked  into  a  groove  in  the  cylinder  itself.  The  pistons 
and  rings  are  of  cast  iron  and  the  crank  case  of  magnalium.  Ignition 
is  by  means  of  a  Bosch  magneto  with  a  special  advance  device  as  it 
is  impractical  to  operate  the  two-cycle  motor  with  a  fixed  ignition 
point,  it  being  necessary  to  retard  the  explosion  timing  considerably 
in  order  to  start  without  danger  of  the  motor  kicking  back.  To 
effect  this  a  helical  gear  is  employed  to  turn  the  armature  of  the 
magneto  with  relation  to  the  drive.  The  four-cylinder  Roberts 


373 


AERONAUTICAL   MOTOR  29 

motor  with  carbureter  and  magneto  weighs  165  pounds  and  develops 
52  horse-power  at  1,400  r.  p.  m.,  while  the  six-cylinder  weighs  220 
pounds  and  develops  78  horse-power  at  1,500  r.  p.  m,.  or  3.17  and 
2.8  pounds  per  horse-power,  respectively. 

Fox.  The  Fox  aero  motor  is  another  two-cycle  type  that  is 
distinguished  by  the  use  of  a  special  fourth  port.  Apart  from  this, 
the  motor  is  of  practically  the  conventional  three-port  type.  This 
fourth  port,  known  as  an  accelerator,  is  an  opening  placed  below  the 
third  port  and  is  designed  to  admit  air  alone,  which  goes  through  a 
by-pass  on  the  side  of  the  cylinder,  where  the  fourth  port  is  uncovered 
by  the  upward  stroke  of  the  piston  immediately  after  the  opening 
of  the  third  port.  The  incoming  fuel  charge  through  the  latter  is 
deflected  toward  the  bottom  of  the  crank  case,  while  the  air  entering 
through  the  fourth  part  is  deflected  upward  and  is  pocketed  under 
the  piston  until  the  opening  of  the  intake  port,  entering  the  explo- 
sion chamber  in  advance  of  the  fuel  charge.  It  accordingly  serves 
to  drive  out  the  exploded  gases  in  advance  of  the  entrance  of  the 
fresh  fuel,  thus  increasing  the  power  and  making  the  motor  more 
economical.  The  external  opening  of  this  fourth  port  is  directly 
controlled  by  the  operator  through  a  lever,  so  that  it  may  be  closed 
entirely,  when  the  motor  will  operate  as  the  usual  three-port  type; 
or  it  may  be  opened  full  when  greater  speed  and  power  are  required, 
which  accounts  for  the  name  given  it.  These  motors  are  built  in 
sizes  ranging  from  36  horse-power,  weighing  150  pounds,  up  to  200 
horse-power,  weighing  850  pounds,  the  cylinder  dimensions  of  the 
smallest  size  (four  cylinders)  being  3  J  by  3|  inches,  and  the  largest 
(eight  cylinders)  6><6  inches,  the  average  weight  per  horse-power 
being  about  4  pounds.  The  cylinders  are  placed  in  line  in  all  the 
sizes. 

Elbridge.  A  two-cycle  motor  with  which  a  number  of  successful 
flights  were  made  by  amateur  aviators  during  1910,  is  the  Elbridge 
aero  special.  This  is  a  four-cylinder,  vertical,  three-port  type  and 
it  is  claimed  by  the  makers  that  it  will  carry  almost  its  maximum 
load  up  to  as  high  a  speed  as  2,000  r.  p.  m.  Without  the  magneto 
it  weighs  slightly  less  than  150  pounds  and  delivers  50  to  60  horse- 
power. 

Rotary  Type.  Adams-Farwell.  The  Adams-Farwell,  Fig.  15, 
which  is  the  prototype  in  this  field,  was  first  used  for  automobiles 


373 


30  AERONAUTICAL   MOTOR 

in  1898  and  has  recently  been  redesigned  for  aviation  purposes. 
In  some  respects  this  motor  is  very  similar  to  the  five-cylinder 
revolving  motors  used  in  the  Adams-Farwell ,  automobile,  having 
the  same  number  of  cylinders,  the  same  single  throw  crank,  the  same 
positive  oiler,  and  the  same  crank  construction.  In  other  respects, 
however,  it  is  quite  different,  being  designed  solely  for  aviation 
purposes,  and  revolving  in  a  vertical  plane,  so  that  it  may  be  direct 
connected  to  propeller  shaft  or  have  the  propeller  mounted  directly 
upon  the  motor  for  aeroplane  work. 

The  most  interesting  improvement  found  on  this  motor  and,  no 


Fig.  15.     Adams-Farwell  Revolving  Aeronautical  Motor 

doubt,  the  most  important  advance  made  in  the  construction  of 
aviation  motors  since  the  introduction  of  the  revolving  cylinder  type, 
is  the  elimination  of  the  carbureter  and  employment  of  fuel  injec- 
tion with  a  means  for  regulating  the  amount  of  gasoline  injected 
into  each  cylinder,  and  insuring  that  all  cylinders  will  receive  exactly 
the  same  mixture.  This  also  makes  it  possible  to  do  away  with  the 
inlet  valve,  and  employ  one  valve  for  both  inlet  and  exhaust,  as  only 
air  is  drawn  in  by  the  suction  stroke  of  the  piston,  whfle  the  gasoline 
is  sprayed  within  the  cylinder  where  it  is  mixed  with  the  charge  of  air 
before  compression.  Having  but  one  valve  in  the  head  of  the  cylinder 
it  can  be  made  amply  large  to  insure  a  full  charge  and  a  free  exhaust. 


374 


AERONAUTICAL   MOTOR  31 

In  order  to  relieve  the  cam  controlling  the  action  of  all  five 
valves  from  the  heavy  load  of  opening  a  large  valve  against  the  high 
pressure  at  the  time  exhaust  takes  place,  the  cylinders  are  provided 
with  auxiliary  exhaust  ports,  which  are  uncovered  by  the  piston  on 
its  downward  stroke.  No  check  valves  are  required  over  these  aux- 
iliary ports,  as,  on  the  suction  stroke,  pure  air  and  not  a  mixture  of 
gas  is  drawn  in,  so  what  air  is  drawn  in  through  the  auxiliary  ports 
on  the  suction  stroke  becomes  a  part  of  the  explosive  mixture  in  the 
cylinder,  and  being  a  constant  quantity  does  not  affect  the  operation 
of  the  motor. 

The  control  of  the  motor  is  entirely  taken  care  of  by  regulating 
the  amount  of  gasoline  used,  and  the  only  adjustment  that  might  be 
construed  as  belonging  to  the  carburetion  system,  is  the  valve  by 
means  of  which  this  control  is  accomplished.  The  motor  is  not  sensi- 
tive to  adjustment,  and  the  speed  may  be  regulated  through  quite 
a  wide  range  by  this  simple  means. 

The  lubrication  system  mentioned  consists  of  a  simple  and  ingen- 
ious oiling  device  that  is  a  patented  feature  of  the  motor  and  repre- 
sents a  great  advance  over  the  present  wasteful  method  of  lubricating 
rotary  motors.  This  oiler  consists  of  a  single  rotary  member  much 
resembling  in  form  the  cylinder  of  a  revolver,  with  longitudinal 
chambers  bored  therein.  Each  of  these  chambers  carries  a  plunger 
which,  as  the  cylinder  revolves,  is  driven  from  end  to  end  by  two 
stationary  cams,  causing  a  small  amount  of  oil  to  be  drawn  in  to  each 
of  the  chambers  at  the  bottom  and  ejected  into  a  corresponding  tube 
at  the  top.  This  piler  supplies  cylinder  oil  of  an  extra  heavy  grade 
to  the  various  bearings  and  to  the  cylinders,  doing  away  with  the 
necessity  for  splash  lubrication,  which  calls  for  the  flooding  of  other 
revolving  cylinder  motors  with  a  great  quantity  of  oil  that  dirties 
the  valves  and  soots  up  the  spark  plugs. 

There  are  two  spark  plugs  in  each  cylinder  of  this  motor,  and 
two  independent  ignition  systems  are  employed,  so  that  either  or 
both  of  the  set  of  plugs  may  be  used,  thus  insuring  against  the 
accidental  stoppage  of  the  motor  from  a  broken  wire. 

Something  over  ten  years  ago,  the  Adams  Company  conducted 
a  series  of  experiments  to  determine  the  action  of  the  air  in  circulating 
about  the  cylinder  of  a  revolving  cylinder  motor,  and,  as  a  result, 
established  beyond  question  the  fact  that  longitudinal  ribs  are  much 


375 


32  AERONAUTICAL   MOTOR 

more  efficient  than  the  circular  type.  The  air  coming  in  contact  with 
the  cylinder  walls  is  thrown  off  radially,  circulating  lengthwise  of 
the  cylinders,  so  the  only  logical  arrangement  of  cooling  ribs  is  length- 
wise of  the  cylinders.  The  placing  of  ribs  in  this  way  has  the  further 
advantage  of  strengthening  the  cylinder  against  tensile  strain  caused 
by  the  action  of  centrifugal  force,  and  the  explosion. 

This  new  motor  operates  satisfactorily  on  low-grade  fuels,  but 
when  these  grades  are  employed,  it  is  desirable  to  have  a  small  tank 
of  gasoline  of  higher  specific  gravity  to  facilitate  starting.  Reliability 
has  been  considered  above  extreme  light  weight,  as  evidenced  by 
the  large  connecting-rod  bearings,  the  liberal  size  of  the  crank  shaft, 
and  the  fact  that  four  rings  are  employed  on  the  piston  where  some 
builders  of  aviation  motors  are  using  only  a  single  ring.  Vanadium 
chrome  nickel  steel  is  used  wherever  practicable.  The  dimensions  are 
6-inch  bore  and  stroke,  and  at  1,000  r.  p.  m.  the  motor  is  rated  at 
72  horse-power.  It  drives  a  9-foot  6-inch  propeller  of  6-foot  pitch 
at  900  to  1,000  r.  p.  m.,  developing  a  thrust  of  440  to  460  pounds, 
which  can  be  maintained  indefinitely  without  overheating  the  motor. 

Brooke  "Non-Gyro"  Motor.  This  is  another  American  motor  of 
the  rotary  type  of  recent  development.  It  is  made  in  Chicago  and 
is  distinguished  by  several  new  features  that  should  make  it  of  value 
for  aeronautical  purposes,  and  particularly  for  aeroplane  work.  The 
Type  "E"  Brooke  motor,  which  lists  at  $2,500,  has  10  cylinders, 
arranged  in  two  units  of  five  each,  either  of  which  may  be  run  inde- 
pendently of  the  other  when  desired.  With  all  10  cylinders  working, 
the  motor  is  rated  at  85  horse-power.  The  cylinders  are  offset  slightly 
on  the  crank  case  and  measure  4J  by  4|  inches.  Two  Stromberg 
carbureters  are  employed,  one  for  each  unit,  while  a  two-cylinder 
type  of  magneto  takes  care  of  the  ignition  of  all  10  cylinders,  there 
being  but  one  foot  of  high-tension  cable  necessary  and  no  moving 
contacts,  making  a  very  simple  and  positive  ignition  system  that 
should  prove  of  great  value,  as  the  ignition  is  a  weak  point  in  even 
the  best  of  motors  and  its  failure  through  trivial  causes  is  hard  to 
guard  against  where  a  number  of  small  parts  and  a  great  deal  of 
wiring  is  necessary.  Another  improvement  is  the  elimination  of  the 
wasteful  method  of  "shooting"  oil  through  the  motor  for  lubrication, 
as  in  the  Gnome,  a  nine-tube,  force-feed  oiler  being  employed  instead. 
The  intake  valves  are  placed  in  the  piston  heads,  while  the  exhaust 


376 


AERONAUTICAL   MOTOE  33 

valves  are  in  the  cylinder  heads.  Light  springs  are  used  to  keep 
the  valves  in  place  when  the  motor  is  idle,  but  they  have  no  function 
to  perform  when  it  is  in  operation. 

Weinberg.  An  interesting  development  of  this  kind  is  the 
Weinberg,  two-cylinder,  horizontal-opposed,  air-cooled  motor,  a 
Detroit  product.  The  crank  shaft  is  stationary  while  the  cylinders 
revolve  about  it,  centrifugal  force  being  taken  advantage  of  to  draw 
in  the  charge  through  the  hollow  shaft  and  to  exhaust  it.  During 
the  outward  stroke  of  the  pistons  a  vacuum  is  created  in  the  crank 
case,  drawing  in  the  mixture  of  fuel  and  lubricating  oil,  a  check 
valve  between  the  carbureter  and  crank  case  preventing  its  escape 
on  the  return  stroke.  When  the  piston  reaches  the  lower  limit  of 
its  stroke,  the  charge  enters  the  combustion  chamber  through  a 
by-pass,  the  motor  accordingly  being  in  reality  a  two-cycle  type  with 
an  independent  exhaust  valve.  The  latter  is  mechanically  opened 
by  means  of  a  rocker  arm.  This  valve  is  located  in  the  cylinder 
head  and  is  very  large — almost  two-thirds  the  cylinder  diameter. 
Centrifugal  force  keeps  it  closed  between  explosions  so  that  no  valve 
spring  is  required.  The  cylinders  and  pistons  are  cast  iron  machined 
all  over,  while  the  crank  case  is  a  one-piece  casting  of  aluminum  alloy. 
The  magneto  is  gear  driven  at  the  same  speed  at  which  the  cylinders 
revolve,  the  current  being  distributed  to  the  spark  plugs  through  a 
revolving  sector.  Both  cylinders  fire  simultaneously. 

Metz.  The  Metz  is  a  four-cycle,  seven-cylinder  revolving  motor 
of  unusually  large  size,  Fig.  16,  the  cylinders  having  a  bore  and  stroke 
of  6J  inches.  It  develops  125  horse-power  at  800  r.  p.  m.  and  weighs 
375  pounds,  or  exactly  3  pounds  per  horse-power.  The  cylinders  are 
of  chrome  steel  machined  direct  from  hollow  forgings  with  very  thin 
integral  flanges  for  air  cooling.  They  are  attached  to  a  drum-shaped 
crank  case  cast  of  alvanum,  another  aluminum  alloy  of  great  strength 
and  lightness,  mounted  on  large  annular  ball  bearings.  The  station- 
ary crank  shaft  and  crank  pin  are  of  chrome  nickel  steel.  Both 
valves  are  placed  in  the  cylinder  heads  and  are  mechanically  operated. 
The  valves  themselves  are  nickel  steel  while  the  push  rods  for  operat- 
ing them  are  light  tubes  of  the  same  metal.  Instead  of  feeding  the 
mixture  up  through  the  pistons  as  in  the  Gnome  revolving  motor, 
it  is  led  from  the  crank  case  to  each  of  the  inlet  valves  through  light 
copper  pipes.  The  fuel  and  lubricating  oil  enter  the  crank  case 


377 


34 


AERONAUTICAL  MOTOR 


through  the  hollow  crank  shaft,  centrifugal  force  being  relied  upon 
to  distribute  the  lubricant.  The  pistons  are  very  light  and  are  fitted 
with  a  novel  type  of  floating  piston  ring. 

Weight  per  Horse=Power  Hour.     It  will  be  noted  that  in  very 
few  of  the  cases  mentioned  does  the  weight  of  the  motor  exceed  four 


Fig.  16.     Metz  Seven-Cylinder  Revolving  Motor  with  Nickel-Steel  Cylinders 

pounds  per  horse-power;  in  the  majority  it  is  between  two  and  a 
fraction  of  this  figure,  or  say  an  average  of  three  pounds.  This,  of 
course,  refers  to  the  motor  alone;  in  the  case  of  water-cooled  motors 
the  addition  of  the  radiator,  water  supply,  gasoline  tank,  and  similar 
fittings  will  usually  increase  the  weight  by  almost  a  pound  per  horse- 
power. Even  at  that  it  will  be  evident  that  improvements  in  con- 
struction and  a  disregard  for  the  cost  of  the  finished  product  have 
accomplished  wonders  where  the  reduction  of  the  weight  is  con- 
cerned. It  is  not  too  much  to  say  that  even  the  heaviest  of  the 


378 


AERONAUTICAL  MOTOR  35 

motors  in  question  is  a  remarkably  light  power  unit.  But  there  is 
a  factor  that  is  of  greater  importance  in  the  result  than  that  of  the 
weight  per  horse-power.  This  is  the  weight  per  horse-power  hour  as 
explained  in  Dirigible  Balloons,  page  25. 

FOREIGN  MOTOR  TYPES 

As  with  the  automobile,  the  French  took  up  the  aeroplane 
and  its  motive  power  with  all  the  energy  and  enthusiasm  they  pos- 
sess, right  from  the  start.  Even  before  the  Wrights  made  their 
first  public  flights  in  France,  interest  was  widespread  and  much 
had  been  accomplished.  The  same  spirit  was  not  infused  into  the 
art  on  this  side  of  the  Atlantic  until  1910  and  even  then  the  number 


Fig.  17.     Deuthil-Chalmers  Two-Cylinder  Air-Cooled  Motor 

of  investigators  devoting  their  attention  to  it,  the  number  of  machines 
in  existence,  and  the  number  of  men  who  could  actually  fly,  were  but 
a  small  fraction  of  those  engaged  in  the  pursuit  of  aviation  in  France. 
This  briefly  explains  why  so  much  attention  has  been  devoted  to  the 
development  of  the  aeroplane  motor  abroad,  as  shown  by  the  follow- 
ing examples,  the  majority  of  which  are  of  French  construction. 

Horizontal=Opposed  Type.  Deuthil-Chalmers.  There  is,  how- 
ever, an  American  note  in  this  development,  if  it  may  be  so  called, 
and  that  is  the  adoption  of  the  two-cylinder,  horizontal-opposed 


379 


36 


AERONAUTICAL  MOTOR 


motor — a  purely  American  type — for  very  light  units.  The  best  rep- 
resentative of  this  class  is  the  Deuthil-Chalmers  20-horse-power,  air- 
cooled  motor  used  to  drive  Santos-Dumont's  Demoiselle.  Following 
the  precedent  of  so  many  other  makers,  later  models  of  this  motor 
are  water  cooled,  Fig.  17.  The  first  air-cooled,  two-cylinder  type 
weighed  but  48.5  pounds,  or  2J  to  2f  pounds  per  horse-power,  while 
the  later  model,  and  particularly  the  four-cylinder  type,  weighs  4 
pounds  per  horse-power.  The  connecting  rods  of  each  pair  of  cylin- 
ders are  attached  to  a  common  crank,  while  instead  of  the  usual  fly- 
wheel, a  wire  spoke  wheel  resembling  bicycle  construction,  is  employed. 
Cylindrical  valves,  both  of  which  are  mechanically  operated,  are 
placed  in  the  heads,  the  cylinders  being  attached  to  the  drum-shaped 


Fig.  18.     Darracq  Two-Cylinder  Motor 

crank  case  by  means  of  long  stay  rods  which  pass  through  clamps 
over  the  cylindrical  heads.  The  spark  plugs  are  placed  in  the  upper 
sides  of  the  heads  with  the  water  outlets  close  to  them,  the  water 
intake  being  on  the  under  side.  Special  oil  feeds  are  run  to  the  cylin- 
ders to  lubricate  the  pistons,  splash  not  being  depended  upon  for 
this  purpose.  The  complete  motor  is  attached  to  the  aeroplane  by 
two  bolts  passing  through  lugs  cast  in  the  crank  case. 

Darracq.  Another  motor  of  this  type  is  the  Darracq,  shown 
in  Fig.  18.  This  is  also  a  water-cooled  motor,  most  of  the  construc- 
tional details  of  which  are  apparent  in  the  photograph.  Both  valves 
are  mechanically  operated  by  rocker  arms  and  push  rods  actuated 


380 


AERONAUTICAL   MOTOR 


37 


by  a  pair  of  eccentrics  completely  housed  in,  this  being  a  distinction 
from  the  general  practice  in  aviation  motors,  the  timing  gears  usually 
being  exposed  as  in  the  original  automobile  motors.  The  magneto 
is  mounted  at  an  angle  on  top  of  the  crank  case,  while  both  the  car- 
bureter and  the  oil  tank  are  suspended  below  it,  a  pump  immersed 
in  the  tank  itself  distributing  the  lubricant. 

Clement.     In  the  Clement  motor  of  this  type,  both  the  oil  and 
water  tanks  are  combined  and  are  mounted  over  the  crank   case, 


Fig.  19.     Clement  Two-Cylinder  Water-Cooled  Motor 

as  shown  by  Fig.  19.  A  similar  valve  action  and  arrangement  of 
the  carbureter  and  intake  piping  are  employed  as  in  the  Darracq, 
while  the  magneto  is  mounted  alongside  the  gear  type  water  pump  at 
the  back  of  the  motor. 

The  next  class  in  what  may  be  termed  the  order  of  development 
is  the  conventional  four-cylinder  vertical  type,  many  of  which, 
however,  are  distinguished  by  unusual  features. 

Conventional  Four=Cylinder  Type.  Wright-Baniquand.  Of  the 
more  conventional  types,  the  Wright-Barriquand  (French  Wright 


381 


38  AERONAUTICAL  MOTOR, 

motor)  differs  from  its  American  prototype  only  in  slight  detail, 
the  principal  feature  being  the  use  of  mechanically-operated  inlet 
valves.  (See  Fig.  20.) 

Panhard  and  Primi-Berthand.     The  Panhard  and  Primi-Ber- 
thand,  Figs.  21  and  22,  are  similar  in  so  far  as  their  cooling  arrange- 


Fig.  20.     Wright-Barriquand  (French  Wright)  Motor 

ments  are  concerned.  That  is,  both  have  light  sheet-copper  jackets 
of  corrugated  section  to  increase  the  radiating  surface.  But  the 
former  is  a  four-cycle  type  with  the  valves  in  the  head  operated  by 
rocker  arms,  while  the  latter  is  a  two-cycle  engine,  as  will  be  apparent 
from  the  photo,  which  illustrates  the  carbureter  and  the  method  of 
drawing  the  fuel  mixture  into  two  outside  chambers,  which  com- 
municate with  the  cylinders  through  the  ports  shown,  these  being 
opened  by  the  pistons  at  the  lower  end  of  the  stroke. 

Vivinus.  The  Vivinus,  Fig.  23,  is  another  aviation  motor 
that  has  been  directly  developed  from  the  automobile  type  of  the 
same  make.  No  attempt  has  been  made  to  achieve  lightness,  the 


382 


'AERONAUTICAL   MOTOR 


39 


motor  weighing  300  pounds  for  an  output  of  only  50  horse-power,  or 
6  pounds  per  horse-power.  But  trials  have  shown  it  to  be  capable 
of  sustained  operation  without 
power  losses,  it  having  been  em- 
ployed successfully  on  a  Farman 
biplane  in  England.  As  the  illus- 
tration shows,  a  pressed-steel  fly- 
wheel is  employed. 

Other  Vertical  Cylinder  Types. 
Motors  of  a  generally  similar 
type,  the  chief  features  of  which 
are  evident  from  the  illustrations, 
are  the  De  Dietrich,  Fig.  24; 
M.  A.  B.,  Fig.  25;  Aster,  Fig.  26, 
and  the  Buchet  six-cylinder, 
wrhich  is  shown  mounted  on  the 
framing  of  a  Bleriot  monoplane 
in  Fig.  27.  It  will  be  noted  that 
the  propeller  in  this  case  is  depended  upon  to  take  the  place  of  the  fly- 
wheel. Practice  shows  this  to  be  permissible  when  six  or  more  cylin- 


Fig.  21.     Panhard  Aviation  Motor 


Fig.  22.     Primi-Berthand  Water-Cooled  Motor 

ders  are  employed,  although  its  omission  is  not  infrequent  even  on  a 
four-cylinder  motor,  as  will  be  noted  by  reference  to  the  Gregoire, 


383 


40  AERONAUTICAL  MOTOR 

mentioned  farther  along.  The  flywheel  also  has  been  eliminated  even 
when  no  more  than  two  cylinders  are  employed  as  in  the  Deuthil- 
Chalmers  horizontal-opposed  type  already  described.  To  say  the 
least,  it  is  not  good  engineering  practice,  particularly  in  two-  and  four- 


Fig.  23.     Vivinus  Aviation  Motor 

cylinder  types,  as  there  is  a  well-defined  interval  between  the  impulses 
in  both  of  these.  In  the  six-  and  eight-cylinder  types  in  which  the 
impulses  always  overlap,  giving  a  continuous  torque,  even  the  slight 
weight  of  the  wood  propeller  blades  revolving  at  such  a  great  distance 
from  the  hub  is  sufficient  to  compensate  for  the  lack  of  a  flywheel, 


384 


AERONAUTICAL   MOTOR 


Fig.  24.     De  Dietrich  Motor 


Fig.  25.     M.  A.  B.  Aviation  Motor 


385 


42 


AERONAUTICAL   MOTOR 


Fig.  26.     Aster  Aviation  Motor 


Fig.  27.     Buchet  Six-Cylinder  Mounted  on  a  Bleriot  Frame 


386 


AERONAUTICAL   MOTOR 


43 


but  it  is  safe  to  say  that  the  operation  of  all  these  motors  would  be 
improved  by  the  use  of  a  fly  wheel,  which  would  add  but  very  slightly 
to  their  total  weight. 


Fig.  28.     Green  Motor  with  Superimposed  Cam  Shaft 

An  instance  of  the  employment  of  a  superimposed  cam  shaft 
is  found  in  the  Green,  Fig.  28,  a  motor  of  English  design,  while 
the  Gregoire,  already  referred  to,  and  illustrated  by  Fig.  29,  shows 
the  use  of  an  integral  radiator  which  permits  of  greatly  reducing  the 
weight  by  cutting  down  the  amount  of  water  required  to  a  fraction 


387 


44 


AERONAUTICAL   MOTOR 


of  that  ordinarily  necessary.  This  radiator  consists  of  four  banks 
of  light  copper  tubes  of  small  diameter  the  forward  sections  of  which 
have  two  rows  of  tubes  while  the  after  ones  have  but  one  row.  These 
tubes  terminate  in  headers  at  top  and  bottom  on  much  the  same 
principle  as  the  water-tube  boiler,  the  upper  or  main  headers  being 
of  considerably  greater  diameter  than  the  lower  ones.  These  headers 


Fig.  29.     Gregoire  Motor  with  Directly  Attached  Radiator 

extend  entirely  across  the  cylinder  heads  and  outboard  for  some 
distance  and  are  connected  with  the  water  jackets  at  the  valves, 
or  hottest  part.  The  lower  headers  are  in  two  parts,  directly  attached 
to  the  lowest  part  of  the  jacket  at  right  angles.  As  the  water  heats  it 
rises  in  the  large,  vertical,  uptake  tubes,  spreads  across  the  upper 
headers  and  drops  through  the  banks  of  small  tubes  which  are  cooled 
by  the  wind,  the  circulation  being  entirely  on  the  thermo-syphon 


388 


AERONAUTICAL   MOTOR  45 

principle.       The  four-cylinder  motor  shown   in   Fig.   30  is  note- 
worthy chiefly  owing  to  the  fact  that  the  very  radical  departure  of 


Fig.  30.     Four-Cylinder  Type  with  Gear  Drive  to  Propeller  Shaft 

incorporating  a  gear  drive  oetween  the  crank  shaft  and  propeller 
connection  as  an  integral  part  of  the  motor  has  been  tried. 


Fig.  31.     100-Horse-Power  Sixteen-Cylinder  Antoinette  Motor 

V=Type.  Antoinette.  From  the  four-cylinder  to  the  eight- 
cylinder  V-type  motor  is  a  logical  step  in  the  problem  of  weight 
saving  as  this  type  permits  of  the  use  of  the  same  form  of  crank  shaft 


389 


46  AERONAUTICAL   MOTOR 

of  scarcely  greater  diameter,  each  opposite  pair  of  cylinders  having 
the  big  ends  of  its  connecting  rods  attached  to  a  common  crank  pin. 
The  Antoinette  is  the  most  prominent  instance  of  this,  a  sixteen- 
cylindei  motor  of  this  class  rated  at  100  horse-power  being  shown  in 
Fig.  31.  One  or  two  of  these  have  been  employed  in  the  Antoinette 
racing  monoplanes,  but  the  eight-cylinder  engine  shown  by  Fig.  32, 
is  more  commonly  employed.  This  is  rated  at  55  horse-power  and 
is  a  later  model  than  the  sixteen-cylinder  motor  shown,  having  the 
cylinder  heads  and  valve  seats  made  in  one  piece  from  light  steel 
drop  forgings,  instead  of  being  cast  separately  as  heretofore.  The 


Fig.  32.     Eight-Cylinder  Antoinette  Motor 

cylinders  are  machined  inside  and  outside  and  the  valves  are  placed 
one  above  the  other  in  chambers,  the  inlet  valves  being  automatic, 
individual  plunger  pumps  being  employed  to  inject  the  fuel  directly 
into  the  valve  opening.  These  pumps  are  operated  by  variable 
throw  eccentrics,  the  travel  of  which  may  be  adjusted  by  means  of 
the  hand  wheel  back  of  the  motor  which  is  within  reach  of  the 
aviator.  This  controls  the  amount  of  power  developed  by  adding 
or  decreasing  the  amount  of  gasoline  in  the  mixture,  instead  of 
throttling  the  latter  as  is  ordinarily  done.  The  water  jackets  are  of 
pure  copper  and  are  deposited  directly  in  place  on  the  cylinders  by 


390 


AERONAUTICAL  MOTOR  47 

an  electrolytic  or  plating  process.  There  are  thus  no  joints  whatever 
and  the  jackets  are  very  light  and  strong,  the  method  of  attaching 
them  to  the  cylinders  being  patented. 

The  water  pump  is  placed  at  the  rear  end  of  the  crank  shaft  in 
a  special  casing,  a  pulley  on  an  extension  of  the  pump  shaft  carrying 
a  belt  which  drives  a  smaller  water  pump  placed  at  the  bottom  of  the 
panel  of  condenser  tubes  which  form  part  of  the  triangular  forward 


Fig.  33.     Fiat  Eight-Cylinder  Air-Cooled  Motor 

part  of  the  body  of  the  Antoinette  monoplane.  These  tubes  are  less 
than  one-half  inch  in  diameter  and  are  extremely  light  and  flexible, 
their  weight  forming  four-fifths  of  the  complete  weight  of  the  con- 
denser, while  the  headers  connecting  the  tubes  constitute  the 
remainder.  Horizontally  mounted  back  of  the  motor  is"  a  cylindrical 
tank  employed  to  separate  the  steam  and  water  coming  from  the 
jackets.  At  the  top  of  this  tank  is  a  pipe  leading  to  the  condenser, 
to  carry  off  the  steam  collecting  in  the  upper  part  of  the  tank.  Upon 
being  retransformed  into  water,  it  is  returned  to  the  tank  by  the 


391 


48 


AERONAUTICAL   MOTOR 


smaller  pump  mentioned.  This  arrangement  makes  it  possible  to 
cool  the  55-horse-power  motor  shown  when  running  constantly 
under  full  load,  with  but  three  gallons  of  water.  The  motor  con- 
verts one-fourth  gallon  of  water  into  steam  per  minute,  the  con- 


Fig.  34.     Renault  Air-Cooled  Eight-Cylinder  Motor.     Fan  Housing  Removed 

denser  having  ample  radiating  surface  to  take  care  of  this.  As 
mounted  along  the  body  of  the  monoplane,  this  condenser  does  not 
add  perceptibly  to  the  head  resistance.  Owing  to  the  flexibility  of 
the  tubes,  it  could  be  mounted  on  the  aeroplane  surfaces  if  desired, 
though  the  location  already  adopted  is  preferable  for  many  reasons. 


393 


AERONAUTICAL   MOTOR  49 

Fiat.  Fig.  33  shows  the  Fiat  eight-cylinder,  V-type,  air- 
cooled  motor,  in  which  the  valve  chambers  are  placed  horizontally 
despite  the  45-degree  angle  of  the  cylinders.  All  the  valves  are 
mechanically  operated  from  a  single  cam  shaft  through  adjustable 
rods  and  levers.  A  separate  high-tension  magneto  is  employed  for 
igniting  each  group  of  four  cylinders,  the  two  magnetos  being  placed 
on  either  side  of  the  crank  case  at  the  rear  and  at  an  angle  of  45 


Fig.  35.     Renault  Air-Cooled  Motor  with  Fan  Housing  in  Place 

degrees.  They  are  driven  by  external  timing  gears  but  are  protected 
from  below  by  the  sheet  aluminum  pan  shown,  the  latter  forming 
one-half  of  the  complete  housing  of  the  motor,  the  upper  part  hav- 
ing been  removed  to  expose  its  details.  A  single  carbureter  placed 
between  the  cylinders  supplies  them  all  with  fuel.  The  normal  r.  p.  m. 
rate  is  very  high — 1,700  to  2,000  r.  p.  m.,  at  which  the  motor  develops 
35  to  40  horse-power,  its  maximum  being  50  horse-power.  The  cylin- 
der dimensions  are  4.3-inch  bore  by  4.1-inch  stroke. 


393 


50 


AERONAUTICAL   MOTOR 


Renault.  Though  of  smaller  dimensions,  3.5-inch  bore  by  4.7- 
inch  stroke,  the  Renault  air-cooled  motor  of  this  type,  shown  in 
Fig.  34,  is  rated  at  45  to  55  horse-power  with  1,500  to  1,800  r.  p.  m., 
the  former  being  its  normal  speed.  In  this  view  it  is  shown  with 
the  air-cooling  apparatus  removed.  All  valves  are  mechanically 
operated  from  a  single  cam  shaft,  the  exhaust  being  placed  directly 
over  the  inlet  valves,  the  inlet  manifold  being  so  arranged  as  to 
obtain  the  maximum  heating  effect  from  the  cylinders.  An  auto- 


Fig.  36.     Pipe  Air-Jacketed  V-Type  Motor 

mobile  type,  automatic  carbureter,  entirely  of  aluminum,  vaporizes 
the  fuel,  and  a  high-tension  magneto  is  employed  to  fire  the  charge. 
As  will  be  noted,  this  carbureter  is  mounted  on  the  upper  side  of 
the  center  of  the  inlet  manifold.  Oil  is  carried  in  a  large  tank  beneath 
the  crank  case  to  which  it  is  raised  by  a  pump  driven  through  bevel 
gearings.  The  motor  is  designed  so  that  the  propeller  of  the  aeroplane 
may  be  mounted  either  on  the  crank  shaft  or  on  the  cam  shaft,  the 
turning  speed  being  reduced  to  one-half  that  of  the  normal  r.  p.  m. 
rate  of  the  motor,  in  the  latter  case,  or  750  r.  p.  m.  This  motor  has 
developed  as  high  as  58  horse-power  on  a  dynamometer  test.  To 


394 


AERONAUTICAL   MOTOR 


51 


cool  it  a  centrifugal  fan  of  large  diameter  is  mounted  in  a  housing  at 
one  end,  as  shown  by  Fig.  35.  The  cold  air  from  the  periphery  of  this 
fan  is  led  between  the  cylinders  by  means  of  the  extended  housing 
shown,  finding  an  outlet  at  the  side  between  the  cooling  flanges  on 
the  cylinders.  Complete  with  magneto,  carbureter,  and  air-cooling 
equipment,  it  weighs  374  pounds,  or  6J  pounds  per  horse-power.  It 
was  with  one  of  these  motors  that  Tabuteau  won  the  Michelin  prize 
of  $20,000  in  1910  by  flying  for  more  than  eight  hours  without  a 
stop,  covering  close  to  400  miles. 
Pipe.  Another  motor  of  the 
same  type  which  is  air  cooled  on 
the  same  principle  as  the  Renault 
is  the  Pipe,  of  Belgian  manufac- 
ture, illustrated  by  Fig.  36.  The 
cylinders  are  100  millimeters 
square,  i.  e.,  3.9  inches  bore  and 
stroke.  The  crank  shaft  is  mount- 
ed on  three  large  ball  bearings 
with  a  ball  thrust  bearing  at  one 
end,  the  cam  shaft  also  being 
similarly  mounted,  with  the  ex- 
ception of  the  provision  against 
thrust.  One  of  the  chief  features 
of  this  motor,  apart  from  the 
cooling,  is  the  combined  inlet  and 
exhaust  valve,  on  the  same  prin- 
ciple as  the  Pelteriei  (French)  and 
the  Franklin  (American)  motors.  It  consists  of  a  sliding  sleeve,  bell 
mouthed  at  its  lower  end  to  form  the  exhaust  valve,  and  the  seat  for 
the  inlet  valve  as  well.  This  is  illustrated  in  section  by  Fig.  37.  The 
inlet  valve  G  is  concentric  with  the  sleeve  S,  its  stem  R  passing  through 
the  hollow  stem  of  S,  and  it  seats  upon  it  at  H.  The  seat  for  S  in 
the  cylinder  head  is  at  J.  The  two  valves  thus  formed  are  provided 
with  suitable  retaining  springs  and  are  operated  by  the  levers  00' 
and  PP'.  P  is  forked  to  surround  R  and  bear  upon  the  cap  V 
surmounting  S.  S  forms  a  piston  and  is  provided  with  two  piston 
rings  just  below  the  inlet  ports  DD,  to  prevent  the  exhaust  gases 
from  leaking  into  the  inlet  pipe  when  being  expelled  through  the 


Fig.  37.      Combined  Inlet  and  Exhaust 
Valve  of  Pipe  Motor 


395 


52 


AERONAUTICAL   MOTOR 


exhaust  ports  EE.  When  G  is  opened  by  the  rocker  arm  0,  gas 
is  drawn  from  the  carbureter  through  DD  and  down  through  the 
hollow  sleeve  S.  At  the  end  of  the  working  stroke,  the  sleeve  S  is 
moved  downward  from  its  seat  at  J  by  the  forked  rocker  arm  P,  the 
exhaust  gases  then  being  expelled  through  the  ports  EE.  The 
passage  of  the  cool  gases  through  the  center  of  S  prevents  both  the 
inlet  and  exhaust  valves  from  warping  due  to  the  heat  and  is  thus 
of  great  advantage  on  an  air-cooled  motor.  Two  blowers  of  special 
form,  one  at  each  end  of  the  crank  shaft,  force  a  large  volume  of  air 
through  the  aluminum  jackets  and  over  the  cooling  flanges  of  the  cyl- 


Fig.  38.     Bruhot  Eight-Cylinder  Water-Cooled  Motor 

inders  similar  to  the  American  Frayer-Miller  engine.  The  Pipe  motor 
complete  weighs  288.8  pounds,  or  about  5|  pounds  per  horse-power. 

Water=Cooled  Types.  Examples  of  water-cooled,  eight-cylin- 
der, V-type  motors  are  illustrated  in  the  Bruhot  (French),  Fig.  38, 
and  the  Wolseley  (English),  Fig.  39,  two  of  the  latter  of  200  horse- 
power each  being  used  on  the  ill-fated  British  airship  Mayfly. 

Fan  and  Star  Types.  Anzani.  It  will  be  noted  that  few,  if 
any,  of  the  four-cylinder  or  eight-cylinder  motors  just  described, 
whether  air-  or  water-cooled,  weigh  less  than  5  pounds  per  horse- 


396 


AERONAUTICAL   MOTOR 


53 


power,  while  most  of  them  exceed  this.  To  considerably  reduce  this 
figure,  the  fan  or  star  arrangement  of  the  cylinders  has  been  resorted 
to.  In  its  simplest  form  this  is  shown  by  the  Anzani  two-cylinder, 


Fig.  39.     Wolseley  Eight-Cylinder  Water-Cooled  Aviation  Motor 

air-cooled  motor,  Fig.  40.    In  reality,  this  is  nothing  more  or    less 

than  a  section  of  the  usual  eight-cylinder  V-type.     Cooling  is  by 

means  of  sheet-metal,  perforated  flanges  pressed  on  the  cylinders. 

M.  A.  B.    A  closer  approach  to  the  fan  formation  is  seen  in  the 


397 


Fig.  40.     Anzani  Two-Cylinder  V-Type  Motor 


Fig.  41.     M.  A.  B.  (Italian)  Four-Cylinder  Motor 


398 


AERONAUTICAL  MOTOR 


55 


M.  A.  B.  (Italian)  four-cylinder  motor,  Fig.  41.     In  this  case,  as 
in  those  following,  the  flanges  are  cast  integral  with  the  cylinders. 

Farcot.  A  further  extension  of  the  same  principle  is  shown  in 
the  Farcot  (French),  Fig.  42,  this  having  six  air-cooled  cylinders. 
The  same  makers  also  manufacture  a  motor  in  which  the  cylinders 
are  mounted  radially  around  a  circular  crank  case,  the  latter  with 
its  cylinders  lying  horizontally,  the  crank  shaft  running  vertically. 
On  its  upper  end  it  carries  a  seven-bladed  horizontal  fan  to  cool 
them. 


Fig.  42.     Farcot  Fan  Type  Air-Cooled  Motor 

This  arrangement  of  cylinders  grouped  symmetrically  around 
a  central  crank  case  is  not  new,  Forest  having  employed  it  in  1888, 
and  Manley  in  1900  for  aeronautic  motors,  the  former  building  a 
50-horse-power,  eight-cylinder  motor  of  this  type  with  the  then 
light  weight  of  1 1  pounds  to  the  horse-power.  Manley  produced  a 
52-horse-power,  five-cylinder  motor  with  a  weight  of  but  2.4  pounds 
per  horse-power,  or  125  pounds  total  weight.  It  developed  full 
power  for  ten  hours  under  constant  load  and  was  subsequently 


399 


56 


AERONAUTICAL   MOTOR 


employed  by  Professor  Langley  in  his  full-sized  aerodrome.  The 
number  of  cylinders  and  their  arrangement  in  a  motor  of  this  type 
have  much  to  do  with  the  balance,  regularity  of  cycle,  lack  of  vibra- 
tion, and  smoothness  of  running.  A  four-cylinder  motor  of  this  type 
is  nearly  in  perfect  balance  so  far  as  centrifugal  force  is  concerned, 
a  suitable  counterweight  making  up  for  any  deficiency.  With  two 
sets  of  four  cylinders  working  on  two  cranks  at  180  degrees,  the 
balance  is  better  still — the  more  so  the  nearer  together  the  planes 


Fig.  43.     Crosa-Section  of  Farcot  50-Hor3e-Power  Air-Cooled  Motor 

of  the  two  sets  of  cylinders.  The  relative  positions  of  the  pistons, 
connecting  rods,  and  cranks  in  an  eight-cylinder  Farcot  motor  of  this 
type  is  shown  in  section,  Fig.  43. 

Each  group  of  four  cylinders  is  necessarily  in  a  different  plane 
to  permit  of  attaching  the  different  connecting  rods  to  the  two 
cranks,  but  by  offsetting  the  rods,  the  distance  between  the  planes 
of  the  two  groups  has  been  reduced  to  one  inch.  The  cranks  are  at 


400 


AERONAUTICAL   MOTOR 


57 


180  degrees  and  alternate  cylinders  are  in  different  planes.    As  the 
crank  shaft  is  vertical,  a  horizontal  shaft  driven  through  bevel  gears 


Fig.  44.     Farcot  Combined  Valves,  Inlet  and  Exhaust  Positions 

at  a  lower  speed  is  provided  for  attaching  the  propeller.     A  com- 
bined exhaust  and  inlet  valve  similar  to  that  of  the  Pipe  is  employed, 


Fig.  45.     R.  E.  P.  (Pelterie)  Five-Cylinder  Motor 

Fig.  44.     Lubrication  is  by  means  of  a  gear  pump  forcing  oil  through 
the  hollow  crank  shaft  and  the  perforations  in  the  latter  leading  up 


401 


58 


AERONAUTICAL   MOTOR 


through  the  connecting  rods.  Two  small,  high-tension  magnetos,  one 
set  a  quarter  turn  behind  the  other,  provide  ignition.  The  Farcot 
eight-cylinder,  horizontal,  circular  motor  is  made  in  three  sizes,  30, 
50,  and  100  horse-power,  the  weight  being  but  2.2  pounds  per  horse- 


k 


Fig.  46.     Gobron-Brill6  Eight-Cylinder  X-Type  Motor 

power.  Both  magnetos  weigh  only  15  pounds,  whereas  the  ordinary 
high-tension  magneto  alone  weighs  25  to  30  pounds.  It  is  claimed 
that  the  50-horse-power  Farcot  motor  may  be  made  to  develop  as 
high  as  70  horse-power  for  a  short  period. 


402 


AERONAUTICAL   MOTOR 


59 


Clement.  The  new  Clement  aeronautic  motor  resembles  the 
Farcot  in  general  arrangement,  but  differs  considerably  in  detail. 
It  has  seven  water-cooled  cylinders,  all  in  the  same  plane,  the  con- 
necting rods  of  which  are  attached  to  a  single  crank.  A  double 
counterweight,  acting  as  a  flywheel,  gives  almost  perfect  balance. 
The  normal  r.  p.  m.  rate  of  the  motor  is  1,200,  but  the  propeller  is 
driven  at  800  r.  p.  m.  by  means  of  a  second  horizontal  shaft  operated 
through  bevel  gearing,  as  in  the  Farcot.  The  cylinders  are  of  spe- 
cially heat-treated  steel,  while  the  heads  are  cast  steel,  screw  threaded 


Fig.  47.     Side  and  Edge-On  Sections  of  Gobron-Brille  Motor 

and  turned  onto  the  cylinders,  after  which  they  are  solidly  welded 
in  place,  thus  eliminating  many  small  fastenings.  The  valves  are 
in  the  heads  and  are  held  on  their  seats  by  small  flat  springs,  the 
rocker  arms  having  the  usual  helical  springs.  The  pistons  are  of 
pressed  steel,  with  convex  heads,  giving  a  combustion  chamber  whose 
general  shape  is  ellipsoidal.  The  valves  are  operated  by  a  single 
cam  revolving  in  the  same  direction  as  the  crank  shaft  and  at  but 
one-eighth  its  speed  through  gearing.  There  are  four  high  points 
and  four  depressions  in  this  large  cam,  corresponding,  respectively, 
to  the  opening  of  the  exhaust  and  inlet  valves,  the  slow  speed  putting 
very  little  wear  on  the  valve-operating  mechanism,  while  the 
occurrence  of  the  impulses  regularly,  two-sevenths  of  a  revolution 


403 


60 


AERONAUTICAL   MOTOR 


apart,  gives  very  smooth  running.  There  are  three  principal  con- 
necting rods,  to  which  the  other  four  are  attached.  These  three  prin- 
cipal rods  are  carried  upon  two  sets  of  balls,  one  upon  the  inner  two 
rings  and  the  third  on  the  intermediate  pair.  The  crank  pin  is 
removable  to  permit  of  slipping  into  place  the  sleeve  to  which  the 
connecting  rods  are  attached.  This  sleeve  carries  the  two  counter- 
weights. The  high-tension  magneto  for  ignition  is  driven  directly 
from  the  crank  shaft  while  a  separate  distributor  runs  at  half  its 

speed.  The  carbureter  is 
located  beside  the  crank  case 
and  connects  by  a  short  pipe 
to  a  common  chamber  in 
which  all  the  inlet  pipes  ter- 
minate. 

The  water-circulating 
pump  is  placed  about  the 
crank  shaft  and  forces  the 
water  directly  to  the  bottom 
of  the  copper  water  jackets, 
which  are  soldered  and 
clamped  in  place.  The  radi- 
ator of  32J  square  feet  of 
radiating  surface  weighs  but 
26J  pounds  with  its  tank  of 
water.  The  cylinder  bore  is 
4.3  and  the  stroke  4.5  inches, 
the  motor  developing  50 
horse-power  at  1,200  r.  p.  m. 
The  diameter  of  the  motor 
overall  is  3  feet  and  its  total 
weight  in  working  order  is  only  154.3  pounds,  or  3.8  pounds  per 
horse-power.  In  general  design  and  arrangement  it  resembles 
the  Manley  motor  of  1900  built  for  Langley's  aeroplane.  The 
first  of  these  Clement  motors  is  mounted  on  the  Clement  mono- 
plane. 

Pelterie.  The  Pelterie  (R.  E.  P.)  is  a  representative  fan  type 
which  attracted  considerable  attention  by  reason  of  its  ingenious 
design  when  first  placed  on  the  market.  It  is  built  in  five-,  seven-, 


Fig.  48.    Gnome  Seven-Cylinder  Revolving  Motor 


404 


AERONAUTICAL   MOTOR 


61 


and  ten-cylinder  models,  one  of  the  first  being  shown  by  Fig.  45. 
They  are  of  25,  35,  and  50  horse-power,  respectively,  the  25-horse- 
power  model  being  the  one  illustrated.  The  cylinders  are  of  the 
same  size  in  all  and  are  very  small,  2.8-inch  bore  by  3.7-inch  stroke. 


Fig.  49.     Detailed  Side  View  of  Seven-Cylinder  Gnome  Motor 

In  the  five-cylinder  type,  all  the  cylinders  are  in  the  same  plane, 
while  in  the  seven-cylinder,  they  are  staggered,  all  the  connecting 
rods  being  attached  to  a  common  crank  pin  by  offsetting.  The  ten- 
cylinder  motor  is  really  two  fives  placed  side  by  side  and  very  close 
together.  Combined  inlet  and  exhaust  valves  of  the  form  already 
described  are  employed.  Two  carbureters  are  employed  on  the  ten- 
cylinder  motor,  with  a  double  magneto. 


405 


62 


AERONAUTICAL   MOTOR 


Gobron=Brille  X=Form.  One  of  the  most  radical  departures 
from  current  practice  is  found  in  the  Gobron-Brille,  Fig.  46,  which 
has  eight  cylinders  arranged  in  X-form,  each  cylinder  having  two 
pistons.  The  explosion  takes  place  between  the  pistons  which  are 
thus  driven  apart,  the  connecting  rods  of  the  inner  pistons  being 


Fig.  50.     End  View  of  Seven-Cylinder  Gnome  Motor,  Giving  Dimensions 

attached  directly  to  the  two-throw  crank  shaft  in  the  usual  manner, 
while  the  upper  pistons  transmit  their  power  to  the  same  cranks 
through  long  connecting  rods  passing  outside  of  the  lower  pistons, 
but  encased  in  a  housing,  so  that  the  exhaust-valve-operating  mechan- 
ism is  the  only  moving  part  in  view.  The  action  of  this  is  illustrated 
by  Fig.  47.  Above  the  exhaust  valves  of  each  group  is  placed  a 


406 


AERONAUTICAL   MOTOR 


63 


double  rocker  arm,  which,  at  each  turn  of  the  shaft,  opens  one  or  the 
other  of  the  two  valves.  To  obtain  the  movement,  each  of  the 
rocker  arm?  e  is  fastened  to  a  shaft  a  which  is  given  a  reciprocating 
movement  by  the  lever  t,  attached  to  its  other  end.  On  the  end  of  t 
is  a  shoe  or  follower,  running  in  one  or  the  other  of  the  two  grooves 


Fig.  51.     Side  View  of  Fourteen-Cylinder  Gnome  Motor 


in  the  double  cam  c,  keyed  in  the  crank  shaft.  The  two  grooves 
cross  at  a  certain  point,  thus  switching  the  shoe  from  one  to  the 
other  alternately.  The  inlet  valves  are  all  automatic,  and  are  fed 
from  a  single  carbureter,  the  inlet  piping  being  so  arranged  that  the 
course  taken  by  the  gas  from  the  carbureter  to  every  one  of  the 
cylinders  is  the  same.  Ignition  is  provided  by  two  magnetos  driv- 


407 


64 


AERONAUTICAL   MOTOR 


ing  through  worm  gearing  and  a  shaft  at  right  angles  to  the  crank 
shaft,  the  magnetos  revolving  in  opposite  directions.  A  gear  pump 
forces  oil  to  all  moving  parts  inside  the  crank  case,  while  a  centrif- 
ugal pump  circulates  the  water,  of  which  but  four  gallons  are  neces- 
sary. It  generates  75  horse-power  on  a  total  weight  of  330  pounds, 
or  1  horse-power  for  every  4.4  pounds,  making  it  one  of  the  lightest 


Fig.  52.     End  View  of  Fourteen-Cylinder  Gnome  Motor,  Giving  Dimensions 

water-cooled  motors.  Automobiles  of  the  same  make  have  been 
equipped  with  motors  operating  on  this  principle,  for  several  years. 
Gnome  Revolving=Cylinder  Type.  While  the  revolving-cylin- 
der motor  has  been  known  for  a  number  of  years — the  Adams-Far- 
well  (American)  being  one  of  the  first  successful  motors  of  this  type 
did  not  come  into  great  prominence  until  1910,  and  this  mainly 
through  the  performance  of  the  Gnome  motor  on  the  numerous 


408 


AERONAUTICAL  MOTOR  65 

French  machines  competing  at  the  International  Meet  (October, 
1910).  The  Gnome  motor  is  built  in  50-  and  100-horse-power 
models,  the  former  of  seven,  shown  in  Figs.  48,  49,  and  50,  and 
the  latter  of  fourteen  cylinders — really  two  seven-cylinder  motors, 
Figs.  51  and  52.  The  weight  of  the  100-horse-power  model  com- 
plete is  220  pounds,  or  2.2  pounds  per  horse-power,  which  appears 
to  be  the  minimum  reached  in  a  practical  unit.  The  material  and 
machine  work  throughout  are  of  the  very  finest,  the  motor  revolving 
in  practically  perfect  balance.  It  is  estimated,  however,  that  the 
seven-cylinder  motor  expends  at  least  7  horse-power  in  overcoming 
the  resistance  of  the  air  due  to  its  revolution,  the  cylinders  having 
air-cooling  flanges  which  taper  broadly  near  the  heads,  thus  present- 
ing considerable  surface.  The  cylinders  are  mounted  symmetrically 
about  a  drum-shaped  crank  case,  as  in  the  Clement,  and  have  large 
exhaust  valves  placed  in  the  heads  and  operated  by  rocker  arms. 
The  inlet  valves  are  placed  in  the  heads  of  the  pistons  and  are  auto- 
matic so  that  centrifugal  force  is  taken  advantage  of  to  draw  in  the 
fuel  as  well  as  to  expel  the  burnt  gases  through  the  exhaust  valves. 
Both  valves  are  counter-weighted  to  neutralize  this  force.  The  bore 
is  about  4.4  inches  and  the  stroke  4.8  inches,  all  seven  connecting 
rods  being  attached  to  a  common  crank  pin,  or  to  a  two-throw  crank 
pin  in  the  fourteen-cylinder  type,  i.  e.,  one  rod  acts  on  the  pin  and 
the  others  are  articulated  to  it.  Fuel  is  admitted  to  the  crank  case 
through  the  hollow  crank  shaft  to  one  end  of  which  the  carbureter 
is  directly  attached,  while  lubricating  oil  is  injected  in  the  same 
manner  by  means,  of  a  two-cylinder  reciprocating  pump,  with  two 
distributors. 

An  improved  model  of  the  seven-cylinder  Gnome  was  brought 
out  during  1911.  This  is  rated  at  70  horse-power  and  the  first  of 
this  type  completed  was  brought  to  the  United  States  by  Earle 
Ovington  on  his  new  Bleriot  monoplane  with  the  "inverse  curve" 
form  of  tail.  It  requires  a  skilled  mechanic,  thoroughly  familiar 
with  the  Gnome  construction,  to  dismount  the  50-horse-power  model, 
but  in  the  new  70-horse-power  model  it  is  only  necessary  to  remove 
a  few  nuts  to  take  off  the  front  half  of  the  crank  case,  leaving  the 
cylinders  readily  detachable,  while  the  method  of  clamping  them 
has  also  been  made  much  more  secure.  The  receptacles  into  which 
the  spark  plugs  are  screwed  are  internally  threaded  steel  tubes 


409 


66  'AERONAUTICAL   MOTOR 

welded  into  the  side  of  the  cylinder  by  a  secret  process,  while  the 
automatic  inlet  valves,  balanced  by  counterweights  to  offset  the 
action  of  centrifugal  force,  are  made  so  that  they  can  be  withdrawn 
through  the  cylinder  heads,  making  it  unnecessary  to  take  down  the 
engine  for  this  purpose.  It  was  with  one  of  the  new  70"horse-power 
Gnome  motors  that  Weyman  won  the  1911  Gordon-Bennett  in  a 
Nieuport  monoplane. 

As  the  motor  revolves  at  1,300  r.  p.  m.  normally,  the  centrifugal 
force  is  terrific  and  the  oil  is  practically  pumped  right  through  the 
motor — or,  in  other  words,  pumped  in  and  thrown  out.  Castor 
oil  is  employed  for  the  purpose  and  the  consumption  is  very  great — 
at  least  half  a  gallon  of  lubricant  being  necessary  for  every  gallon 
of  gasoline  used.  The  consumption  of  fuel  is  also  very  high — 300 
grammes  per  horse-power  hour — about  10.6  ounces  of  gasoline,  or 
about  44.1  pounds  per  hour  for  the  50-horse-power  motor  and  close 
to  90  pounds  per  hour  for  the  100-horse-power  motor,  which,  with 
lubricant,  would  make  100  pounds  of  gasoline  and  oil  to  run  the  larger 
motor  one  hour.  This  extravagant  consumption  of  fuel  and  oil, 
particularly  such  high-priced  lubricant  as  castor  oil,  is  the  chief 
drawback  of  the  revolving-cylinder  motor,  and  the  latter  will 
undoubtedly  have  to  be  improved  in  this  respect  if  it  is  to  main- 
tain its  lead. 

More  than  500  Gnome  revolving  motors  have  been  built  and 
it  has  to  its  credit  almost  every  world's  record  for  1910  except  that 
of  altitude  (Wright),  and  including  such  events  as  the  Gordon- 
Bennett  Cup,  London  to  Manchester,  Paris-London,  Crossing  the 
Alps,  Statue  of  Liberty,  Circuit  de  L'Est,  and  other  important  speed, 
as  well  as  altitude,  and  endurance  flights,  more  than  $500,000 
in  prize  money  having  been  won  during  1910  alone  in  machines 
equipped  with  Gnome  motors. 


410 


AERIAL  PROPELLER 

Volumes  have  been  written  on  the  theory  and  design  of  the 
screw  propeller  as  applied  to  marine  practice,  yet  after  so  many 
years  of  actual  use  there  are  still  many  things  that  remain  to  be 
definitely  settled.  A  change  in  the  condition  of  operations  renders 
previous  data  of  little  value,  as  in  the  case  of  the  adoption  of  the 
high-speed  turbine  for  marine  propulsion,  the  "Mauretania"  having 
been  equipped  with  no  fewer  than  three  different  sets  of  screws  since 
she  was  first  put  in  service.  It  is,  accordingly,  not  to  be  greatly 
wondered  at  that  there  should  be  a  conflict  of  opinion  where  the 
aerial  propeller  is  concerned.  Obviously,  the  propeller  is  no  less 
important  an  essential  than  the  planes  themselves,  for  support  in 
an  aeroplane  is  entirely  dependent  upon  speed.  To  obtain  speed, 
thrust  is  necessary,  and  it  is  the  function  of  the  propeller  to  produce 
it.  How  this  may  be  done  most  efficiently  is  the  object  of  an  endless 
amount  of  research  that  is  being  carried  on  at  the  present  time. 
The  purpose  of  the  present  subject  is  to  reflect  current  practice — 
to  give  as  far  as  possible  the  data  upon  which  the  designs  of  the  most 
successful  propellers  are  based,  to  show  how  the  propellers  themselves 
are  made,  and  why  they  are  so  made,  as  drawn  from  actual  experience 
rather  than  from  purely  theoretical  ideas. 

In  view  of  the  imperfect  engineering  knowledge  extant  on  the 
subject  at  this  late  d^y,  it  appears  rather  marvelous  that  the  scientist- 
philosopher  Leonardo  da  Vinci  should  have  proposed  the  use  of  the 
propeller  in  one  of  the  aerial  navigation  schemes  which  came  up  in 
his  day — more  than  four  hundred  years  ago.  Of  course,  the  pro- 
peller as  it  exists  today  was  not  known  then,  but  the  screw  principle 
upon  which  it  is  based  is  centuries  old.  In  fact,  General  Meusnier's 
conception  of  the  turning  oars  in  his  plan  for  a  dirigible  balloon 
antedates  the  actual  use  of  the  propeller  for  marine  service  by  many 
years,  and  was  likewise  a  strikingly  approximate  anticipation  of  the 
aerial  propeller  of  the  present  day. 

Factors  in  Propeller  Action.  Pitch.  Before  taking  up  the 
design  or  construction,  the  essential  features  of  a  propeller  should  be 

Copyright,  1912,  by  American  School  of  Correspondence. 


411 


P/TCH 


\ 


Fig.  1.     Diagram  Showing  Pitch 
of  a  Propeller 


2  AERIAL   PROPELLER 

considered  in  order  that  the  technical  terms  referring  to  them  may  be 
intelligible.  As  its  name  indicates  the  screw  propeller  is  based  upon 
the  principle  of  the  screw  thread.  Pitch  in  a  propeller  is  exactly  the 

same  thing  as  the  pitch  of "  a  screw 
thread,  in  other  words,  the  distance 
traversed  by  the  thread  along  the  screw 
in  one  complete  revolution.  When  a  nut 
is  turned  on  or  off  a  bolt,  it  moves  a 
certain  distance  along  the  bolt  for  each 
turn,  and  this  distance  is  its  pitch.  It 
can  not  move  more  or  less  because  its 
movement  is  confined  to  the  thread.  But 
with  reference  to  a  propeller,  Fig.  1,  this 
distance  is  a  purely  theoretical  measure- 
ment, as  the  substance  upon  which  it  acts 
is  yielding,  whether  air  or  water.  How- 
ever, as  the  laws  relating  to  fluids  a're,  for 

the  most  part,  applicable  to  all  fluids,  whether  liquid  or  gaseous, 
advantage  has  been  taken  of  the  accumulated  knowledge  of  marine 
engineering,  to  discover  the  best  means  for  designing  propellers  for 
the  aeroplane. 

Slip.  It  is  a  fact  that  a  propeller  in  water  does  not  practically 
advance  the  distance,  or  propel 
the  vessel  to  which  it  is  attached, 
the  distance  represented  by  its 
pitch.  The  difference  between 
this  and  the  actual  result  .ob- 
tained is  designated  by  the  term 
"slip."  (See  Fig.  2.)  As  slip  repre- 
sents lost  energy  and  a  propeller 
with  a  high  percentage  of  slip 
would  be  very  inefficient,  it  would 
appear  to  be  desirable  to  reduce 
this  factor  to  the  minimum. 
However,  this  is  not  the  case. 
If  there  were  no  slip,  there  could  be  no  reaction  on  the  volume  of 
air  or  water  being  driven  backward  by  the  propeller,  and  there 
would  consequently  be  no  thrust,  so  that  if  the  slip  be  reduced  too 


Fig.  2.   Diagram  Showing  Correction  for  S  ip 


412 


AERIAL  PROPELLER  3 

far,  the  propeller  would  again  be  inefficient.  At  any  rate,  such  is 
the  conclusion  drawn  from  marine  practice,  where  it  is  customary 
to  regard  a  slip  of  10  to  20  per  cent,  i.  e.,  an  efficiency  of  80  to  90 
per  cent,  as  being  representative  of  the  most  economical  results 
obtainable.  In  the  case  of  the  aerial  propeller,  slip  up  to  25  per 
cent  is  considered  good,  40  per  cent  bad,  and  about  15  per  cent  the 
most  economical. 

Aside  from  the  diameter  the  element  on  which  the  friction 
losses  depend  almost  entirely,  is  the  pitch.  Aeroplane  propellers 
fastened  directly  to  the  crank  shaft  of  the  motor  must  of  necessity 
have  a  smaller  pitch,  while  those  driven  by  intermediate  gearing  or 
chains  and  sprockets  may  be  given  a  large  pitch  when  desired.  The 
motor  must  run  at  a  high  speed  in  order  to  develop  its  power  without 
excessive  weight,  and  if  a  propeller  of  large  pitch  be  secured  directly 
to  the  shaft,  it  would  offer  so  much  resistance  that  the  motor  would 
not  reach  its  normal  speed.  The  usual  speed  of  aeronautic  motors  is 
around  1,200  r.  p.  m.  If  the  aeroplane  makes  a  speed  of  40  miles  an 
hour  the  pitch  of  the  direct-connected  propeller  will  be  from  3J  to  5 
feet,  while  on  a  machine  like  the  Wright  biplane,  the  propeller  turns 
at  450  r.  p.  m.  and  the  pitch  is  nearer  10  feet. 

The  friction  and  head  resistance  of  the  propeller  blades  passing 
through  the  air  vary  approximately  as  the  square  of  the  velocity. 
If  the  two  propellers  each  had  a  diameter  of  8  feet,  the  mean  velocity 
of  the  blades  of  the  small  pitch  propeller,  through  the  air,  would 
be  about  2.8  times  as  great  as  that  of  the  large  pitch  propeller,  and 
the  loss  of  power  resulting  from  friction  and  head  resistance  would 
be  about  eight  times  as  great.  For  this  reason,  it  is  desirable  to  make 
the  pitch  large  and  keep  down  the  revolutions  as  compared  with 
speed.  On  the  other  l4and,  if  the  pitch  be  made  too  large,  the  air 
is  pushed  around  sidewise  instead  of  being  pushed  to  the  rear,  and 
as  such  motion  of  the  air  does  not  produce  thrust,  excessive  power 
is  lost  in  that  manner.  With  air  propellers,  as  with  marine  propellers, 
it  has  been  found  that  the  best  pitch  is  from  1.2  to  1.5  times  the 
diameter.  There  is  also  a  practical  disadvantage  in  making  the  pitch 
too  large,  and  this  is,  that  the  starting  thrust,  before  the  aeroplane  has 
got  up  to  speed,  is  considerably  less  than  with  finer  pitch  propellers. 

Thrust.  Thrust  is  work  done  by  the  propeller  in  moving  the 
aeroplane,  and  is  equal  to  the  weight  of  the  mass  of  air  acted  on 


413 


4  AERIAL   PROPELLER 

per  second  times  the  slip  velocity  in  feet  per  second.  This  is  dynamic 
thrust.  The  effort  of  the  same  propeller  on  the  column  of  air  in  which 
it  acts  when  standing  still,  is  termed  static  thrust.  An  illustration  of 
the  difference  between  the  two  may  be  drawn  from  the  starting  of 
an  aeroplane  from  the  ground.  While  held  prior  to  running  over 
the  ground,  the  screw  is  exerting  static  thrust.  The  moment  the 
machine  is  released,  it  begins  to  exert  dynamic  thrust  in  that  it  is 
then  forcing  the  aeroplane  ahead.  It  is  generally  conceded  that 
the  amount  of  static  thrust  a  certain  propeller  is  to  exert  affords 
no  definite  measurement  of  what  it  is  capable  of  doing  when  driv- 
ing the  machine  through  the  air,  or  rather  that  its  static  thrust  will 
be  much  greater  than  its  dynamic,  although  Sir  Hiram  Maxim 
states  that,  as  the  result  of  his  experiments,  both  were  found  to  be 
the  same.  The  thrust  of  the  propeller  in  question  was  said  not  to 
vary  whether  it  was  traveling  through  the  air  at  a  velocity  of  40 
miles  an  hour,  or  standing  stationary,  the  r.  p.  m.  rate  of  the  motor 
remaining  constant.  The  explanation  is  that  when  traveling,  the 
propeller  is  constantly  advancing  on  to  undisturbed  air  and  that 
while  the  slip  velocity  is  reduced,  the  undisturbed  air  is  equivalent 
to  acting  upon  a  greater  mass. 

The  factors  affecting  the  thrust  given  by  a  propeller  are:  First, 
the  diameter,  blade  area,  and  pitch  or  blade  angle,  which  may  be 
termed  propeller  characteristics;  second,  the  speed  of  revolution, 
which  is  proportionate  to  the  engine  driving  power;  and  third,  the 
rate  at  which  the  characteristics  of  the  vessel  will  allow  the  propeller 
to  move  through  the  fluid.  The  propeller  which  is  the  most  efficient 
is  naturally  the  one  which  will  produce  the  greatest  amount  of  thrust 
in  proportion  to  the  power  transmitted  it  by  the  engine,  both  when 
revolving  in  a  fixed  position  on  the  ground  and  when  traveling  through 
the  air.  Each  of  the  factors  mentioned  must  be  provided  for  in  the 
design.  A  propeller  which  is  too  large  or  of  too  great  a  pitch  for  a 
given  motor,  will  effectually  prevent  the  motor  from  developing 
its  normal  power  by  retarding  the  r.  p.  m.  rate.  Propeller  blades 
that  are  not  given  sufficient  area  or  pitch  will  permit  the  engine  to 
race  through  not  imposing  sufficient  load  on  it,  and  if  the  speed 
becomes  greatly  excessive,  the  blades  are  likely  to  burst  or  fly  apart 
through  centrifugal  force.  Should  the  engine  be  too  powerful  for 
the  propeller,  the  blades  may  bend  and  break  under  the  strain. 


414 


AERIAL   PROPELLER  5 

Pitch  Ratio.  Another  characteristic  having  an  important  bear- 
ing on  the  result  is  the  pitch  coefficient,  or  pitch  ratio,  as  it  is  frequently 
termed.  There  is  a  certain  analogy  between  the  propeller  and  the 
main  planes  in  that  both  are  intended  to  drive  through  the  air  easily 
and  at  the  same  time  exert  a  sufficient  hold  on  the  air  either  for  the 
purpose  of  support,  as  in  the  latter  instance,  or  for  driving,  as  in 
the  former.  Pitch  ratio  is  consequently  analogous  to  aspect  ratio. 
It  is  the  ratio  that  the  pitch  bears  to  the  diameter,  or  length  of  the 
propeller.  The  pitch  coefficients  of  eighteen  well-known  monoplanes 
and  biplanes  vary  from  0.4  to  0.2,  the  mean  value  being  0.62,  which, 
as  it  so  happens,  is  exactly  that  of  the  Farman  propeller.  'The  pitch 
ratio  of  the  Wright  propeller  is  said  to  be  1,  and  its  unusually  high 
efficiency  is  generally  conceded,  though  very  few  builders  have 
apparently  considered  it  expedient  to  adopt  the  means  that  make 
this  efficiency  possible,  i.e.,  propellers  of  large  pitch  and  diameter 
turning  at  the  very  slow  speed  of  450  r.  p.  m.  The  propeller  of  the 
Bleriot  XI  has  a  pitch  ratio  of  0.4,  but  it  is  designed  to  run  at 
1,350  r.  p.  m. 

Diameter.  The  diameter  is  affected  by  structural  considera- 
tions, the  placing  of  the  motor  and  other  conditions,  which  restrict 
the  size  of  propeller  that  can  be  employed  on  a  certain  machine.  Dif- 
ferent experimenters  have  widely-differing  standards  in  this  respect, 
as  witness  the  use  of  4-foot  extremely  high-speed  propellers  on  some 
machines  and  8-foot  slow-speed  propellers  on  others.  The  disad- 
vantage of  using  a  very  small  propeller  is  now  generally  recognized, 
however,  and  few,  if  any,  of  less  than  G-foot  diameter  are  employed. 
The  question  of  efficiency  is  so  largely  dependent  upon  the  diameter, 
that  we  may  look  for  an  increase  rather  than  a  decrease  in  the  machines 
of  the  future.  In  fact,  the  whole  question  of  the  efficiency  of  the 
2-bladed  aerial  propeller  seems  to  be  one  of  diameter  and  speed. 
Speaking  in  general  of  properly-designed  concave  propellers,  a  pro- 
peller of  large  size  and  slow  speed  is  always  more  efficient,  all  other 
things  being  equal.  Reduce  the  diameter  and  increase  the  speed 
and  the  efficiency  drops  off  very  rapidly — from  as  high  as  50  pounds 
thrust  per  horse-power  to  as  low  as  6  pounds  per  horse-power,  these 
figures  being  the  result  of  experiments  carried  out  especially  to  estab- 
lish the  effect  of  altering  the  relation  of  these  two  essentials  of  design. 
The  falling  off  in  the  efficiency  at  high  speeds  is  remarkable,  for 


415 


'6  AERIAL  PROPELLER 

while  it  seems  possible  with  the  best  designs  to  obtain  as  high  as 
40  to  50  pounds  thrust  per  horse-power,  the  average  modern  aero- 
plane has  a  screw  of  one-sixth  this  efficiency,  or  about  7  pounds  per 
horse-power. 

Peripheral  Speed.  The  limiting  factor  in  the  propeller  is  its 
peripheral  rather  than  its  rotational  speed,  since  it  is  upon  this  that 
the  centrifugal  stresses,  which  are  by  far  the  most  severe  of  all 
involved,  depend.  The  propellers  of  practically  all  aeroplanes  built 
so  far  run  at  peripheral  speeds  ranging  from  12,000  to  40,000  feet 
per  minute,  with  occasional  instances  of  speeds  as  high,  as  50,000 
feet  per  minute,  the  rotational  speeds  being  so  adjusted  to  the  diam- 
eters of  the  propellers  as  to  produce  little  variation  outside  of  the 
range  given.  At  the  higher  of  the  speeds  mentioned,  nearly  570 
miles  per  hour,  centrifugal  force  is  so  great  as  to  test  to  its  utmost 
the  quality  of  the  finest  structural  material  obtainable. 

That  it  is  better  to  gain  permissible  peripheral  speeds  by  the 
use  of  large  diameter  propellers  at  low-rotational  speeds,  rather 
than  with  small  propellers  at  high-rotational  speeds,  becomes  very 
evident  with  a  little  study.  Take,  for  example,  the  case  of  a  portion 
of  a  propeller  surface,  1  foot  long  and  1  foot  wide,  traveling  edgewise 
round  a  30-foot  circumference,  600  times  a  minute,  it  being  assumed 
that  a  peripheral  speed  of  18,000  feet  per  minute  is  the  maximum 
permissible  in  the  case  in  question.  Under  the  conditions  stated, 
the  surface  passes  any  given  point  10  times  per  second — often  enough 
to  produce  a  material  disturbance  of  the  air  worked  against.  Now 
assume  the  circumference  reduced  to  15  feet  by  a  corresponding 
halving  of  the  propeller  diameter,  and  immediately  it  becomes  apparent 
that  a  doubling  of  the  rotational  speed  is  allowed  without  increasing 
the  peripheral  speed. 

But,  under  the  new  conditions,  the  assumed  propeller  surface 
passes  any  given  point  20  times  per  second,  twice  as  often  as  before 
with  a  correspondingly  reduced  assurance  of  finding  undisturbed 
air  to  work  against.  Moreover,  since  the  blade  surface  travels  the 
same  distance  in  the  same  time  in  both  cases,  there  is  no  oppor- 
tunity to  reduce  its  area  on  account  of  the  higher  rotational  speed 
in  the  smaller  propeller.  The  result  is  that  the  blade  which  is  of  a 
width  only  ^V  the  length  of  its  path  in  the  large  propeller,  is  in  the 
smaller  one  yV  its  length — a  condition  that  operates  directly  against 


416 


AERIAL   PROPELLER 


maximum  effectiveness.  Of  course,  it  may  be  urged  that  when  a 
propeller  is  traveling  through  the  air  under  its  normal  condition  of 
operation,  instead  of  revolving  in  a  circle,  as  when  kept  from  advanc- 
ing, the  blades  travel  separate  helical  paths,  wholly  distinct  from 
one  another.  But  these  paths  are,  nevertheless,  closely  adjacent 
and  become  more  so  with  every  increase  in  the  number  of  blades 
and  every  decrease  in  the  pitch.  From  these  considerations,  it  will 
be  evident  that  large  diameters  and  a  minimum  number  of  blades 
reduce  the  frequency  of  the  air  disturbance  and  tend  to  eliminate 
interference.  The  largest  propeller  built  thus  far,  to  the  writer's 
knowledge,  was  turned  out  in  the  fall  of  1910  for  a  monster  2,200- 
pound  aeroplane  at  that  time  building  in  California.  This  propeller 
measured  14J  feet  in  diameter,  with  a  corresponding  coarse  pitch, 
as  compared  with  the  6-  to  8-foot  propellers  commonly  employed. 
The  air  acted  on  by  the  propeller  is  limited  to  that  which  flows 
through  the  circle  described  by  the  tips  of 
the  blades,  frequently  referred  to  as  the 
disk,  Fig.  3.  The  amount  acted  upon, 
therefore,  increases  with  the  diameter, 
and  as  the  thrust  depends  directly  upon 
the  volume  of  air  and  the  velocity  at 
which  it  is  displaced  to  the  rear,  it 
follows  that  the  greater  the  diameter  the 
less  the  rearward  velocity  need  be  to  ob- 
tain a  given  thrust.  Thus  approximately 
the  same  thrust  will  be  obtained  from  an 
8-foot  propeller  which  imparts  a  5-mile  velocity  to  the  air,  as  from 
a  4-foot  propeller  that  imparts  a  20-mile  velocity.  It  is  self-evident 
that  of  the  total  power  developed  by  the  motor  only  a  part  is 
actually  utilized  in  forcing  the  machine  ahead  through  the  air — the 
remainder  does  no  useful  work  and  is  lost.  A  considerable  portion 
of  this  lost  energy  is  contained  in  the  air  which  has  been  pushed  to 
the  rear  by  the  propeller.  The  amount  of  such  lost  power  increases 
as  the  square  of  the  velocity  at  which  it  is  pushed  astern.  In  the 
4-foot  and  8-foot  propellers  compared  above,  it  is  found  that  when 
developing  the  same  thrust  at  a  speed  of  40  miles  per  hour,  the 
amount  of  lost  power  in  the  case  of  the  smaller  one  is  about  three 
times  as  great  as  in  that  of  the  larger  one.  This  is  the  underlying 


Fig.  3.     Diagram  Showing  Effect- 
ive Area  of  Propeller  Influence 


417 


8 


AERIAL   PROPELLER 


reason  why  small  propellers  are  inefficient  when  used   to  develop 
relatively  high  thrust. 

Power  of  Propellers.  To  obtain  thrust  from  a  propeller,  it 
must  waste  some  power,  for  reasons  that  have  already  been  mentioned 
—it  is  essential  to  thrust  some  air  at  least  to  the  rear.  The  smallest 
quantity  that  it  is  necessary  to  waste  can  be  figured  out,  and  this 
added  to  the  useful  power  gives  the  minimum  amount  of  power 
which  would  be  required  with  a  perfect  and  frictionless  propeller. 


LEAST   POSSIBLE  POWfff  ff£QU/ffED  FOff  AN 8 FT 


(a)rOffA  4 FT.  FffOfKLLER 
A  T  60  WLES  f£ff  WL/ft 


eoo 

fNFOUMDS 


300 


Fig    4.      Minimum  Power  Required  for  8-Foot  Propeller  at  Various 
Thrusts  and  Speeds 

The  curves  in  Fig.  4  show  this  least  power  for  an  8-foot  propeller 
at  different  thrusts  and  at  speeds  of  from  30  to  60  miles  an  hour. 
As  a  matter  of  fact,  no  propeller  can  be  expected  to  reach  the  theo- 
retical limit.  Many  of  the  best  air  propellers  require  about  25  per 
cent  more  power  than  that  shown  by  the  curves  in  Fig.  4,  and  in 
fact,  the  curves  in  Fig.  5,  which  show  the  power  which  will  be 
needed  for  a  good  type  of  propeller,  have  been  prepared  by  adding 
25  per  cent  to  the  theoretical  power  required  in  each  case.  For 


418 


AERIAL   PROPELLER 


9 


example,  from  the  curves  in  Fig.  5,  at  a  speed  of  40  miles,  a  thrust 
of  100  pounds  should  be  obtained  with  14.7  brake  horse-power. 
The  Wright  Brothers  obtain  this  thrust  with  about  15  horse-power, 
which  agrees  practically  with  the  above. 

In  Fig.  4,  the  dotted  line  shows  the  minimum  power  theoret- 
ically necessary  for  a  4-foot  propeller  at  a  speed  of  60  miles  and  at 


60 


50 


- 


/o 


rowff?  f?EQu/fftD  roff  AN  err. 

OrB£ST  TYFL 
AND  5PEED5 


SO 


/oo  /so          zoo 

'  TH/rVST  MrOUMDS 


eso 


300 


Fig.  5.      Actual  Power  Required  for  8-Foot  Propel  er  at  Various  Thrusts  and  Speeds 

different  thrusts.  At  a  thrust  of  200  pounds,  41  horse-power  is 
necessary,  while  for  an  8-foot  propeller  only  35  horse-power  is  required. 
That  is,  at  this  speed  and  thrust,  the  smaller  propeller  requires  20 
per  cent  more  power  than  the  larger  one. 

This  particular  compromise  of  using  a  small-diameter,  high- 
speed screw  to  suit  the  rest  of  the  design  has  cost  the  present-day 
aeroplane  an  enormous  toll.  It  makes  it  necessary  to  carry  a  motor 
several  times  more  powerful  and  heavy  than  it  should  be,  with  a 


419 


10  AERIAL   PROPELLER 

consequent  increase  in  the  size  of  the  aeroplane  itself  in  order  to 
carry  the  extra  weight.  The  large-diameter,  slow-speed  screws  of 
the  Wright  machines  are  undoubtedly  the  chief  basis  of  the  unusually 
high  efficiency  that  they  show.  Langley  demonstrated  that  1  horse- 
power, properly  applied,  could  carry  200  pounds  at  40  miles  per 
hour.  But  what  machine  approaches  this?  On  the  same  basis,  the 
Wright  machine  should  theoretically  be  able  to  fly  with  a  7-horse- 
power  motor,  2  horse-power  being  allowed  for  overcoming  the  resist- 
ance of  the  non-supporting  surfaces,  such  as  the  struts,  guy  wires, 
and  the  like,  while  5  horse-power  would  be  all  that  is  needed  to  drive 
it  through  the  air  at  its  usual  speed.  But  this  would  entail  propellers 
of  great  diameter,  turning  at  a  slow  speed,  and  they  are  not  com- 
patible with  the  rest  of  the  design.  If  they  were,  it  seems  that  a 
tremendous  saving  could  be  effected;  the  weight  of  the  engine  could 
be  greatly  reduced  and  the  radius  of  action  of  the  machine  increased 
at  least  threefold. 

If  allowance  be  made  for  the  difference  in  the  weights  of  a  cubic 
foot  of  water  and  a  cubic  foot  of  air,  and  the  speed  is  changed  from 
knots  to  miles  per  hour,  the  corresponding  formula  for  air  propellers 
is 

33  V?7 


d= 


V 


For  a  thrust  of  100  pounds  and  a  speed  of  40  miles  per  hour, 
the  diameter  would  be 


=8z  feet 


40 

This  agrees  in  practice  with  the  results  obtained  by  the  Wright 
Brothers,  who  use  an  8J-foot  propeller  for  this  thrust  and  speed. 
The  dotted  line  in  Fig.  5  shows  this  relation  for  an  8-foot  pro- 
peller. The  line  crosses  the  power  curve  for  a  speed  of  60  miles  at 
a  thrust  of  210  pounds,  and  that  should  be  the  thrust  of  about  the 
best  efficiency.  At  a  speed  'of  40  miles  the  best  efficiency  would  be 
obtained  with  a  thrust  of  about  95  pounds. 

From  the  above  it  appears  that  the  larger  the  diameter  the  better, 
and  this  would  be  true  but  for  friction  and  head  resistance  of  the  air 


420 


AERIAL   PROPELLER  11 

to  the  propeller  blades.  This  increases  as  the  diameter  is  increased, 
and  the  power  lost  from  this  cause  soon  becomes  as  great  or  greater 
than  that  carried  away  by  the  air  in  the  propeller  race  or  wake. 
With  other  conditions  equal  and  developing  the  same  thrust,  an 
8-foot  propeller  will  lose  from  frictional  and  head  resistance  about 
twice  as  much  power  as  a  4-foot  propeller.  This  makes  it  apparent 
that  the  relation  between  the  diameter,  speed,  and  thrust  is  an 
important  one.  If  the  diameter  is  small,  there  is  excessive  loss  of 
power  in  the  propeller  race,  while  if  too  large,  the  frictional  losses 
are  very  high,  so  that  a  compromise  is  necessary.  In  water  it  has 
been  found  that  when  cavitation  does  not  occur,  the  most  effective 
diameter  is  given  by  the  formula 


V 

where  d  is  the  diameter  in  feet,  T  the  thrust  in  pounds,  and  V  the 
speed  of  the  vessel  in  knots. 

Propeller  Blades.  The  next  characteristic  is  the  blade.  Leon- 
ardo's propeller  was  a  screw  or  helix  of  a  single  worm  or  thread  — 
being  practically  all  ivorm,  and  constituting  an  entire  convolution, 
of  which  the  modem  equivalent  would  be  a  single-bladed  screw, 
blades  being  a  much  later  development.  It  is  easy  to  realize  how  the 
original  screw  propeller  came  to  be  of  the  single  worm  type,  and  why 
one  complete  turn  was  deemed  essential.  It  was  first  discovered  by 
actual  experiment  that  half  a  convolution  was  fully  as  efficient  as 
a  whole  turn,  then  that  a  quarter  turn  was  more  efficient  than  half, 
but  with  this  curtailing  of  the  helix  a  formidable  difficulty  arose. 
It  had  now  developed  into  a  1-bladed  screw,  was  unsymmetrical 
and  consequently  unbalanced.  Centrifugal  force  and  1  -sided  thrust 
now  jointly  interposed  with  inimical  results.  It  finally  appeared  that 
to  produce  a  more  efficient,  compact,  and  symmetrical  screw  pro- 
peller, while  employing  only  a  fraction  of  a  convolution,  two  or  more 
worms  were  necessary  —  in  other  words,  blades.  Thus  it  gradually 
came  to  pass  that  the  modern  aerial  true-screw  propeller  is  but  a 
very  short  length  cut  off  a  2-threaded  screw,  in  which  the  thread  is 
relatively  deep,  with  a  pitch  equal  to  about  two-thirds  its  diameter. 
A  marked  later  tendency  was  to  err  on  the  side  of  plurality  of  blades, 


421 


12  AERIAL   PROPELLER 

and  this  was  still  in  evidence  when  propellers  first  came  to  be  used 
for  aerial  propulsion. 

Thus  the  Ericsson  marine  propeller  was  formed  of  a  short  sec- 
tion of  a  12-thread  screw  of  very  coarse  pitch  and  naturally  proved 
very  inefficient.  The  aerial  fan  propeller  of  Moy  had  six  broad  vanes 
enclosed  within  a  hoop,  and  was  not  a  screw  at  all.  It  was  little 
better.  The  same  remarks  apply  to  the  propellers  of  Henson,  String- 
fellow,  Linfield,  du  Temple,  and  many  others.  Even  the  first  pro- 
peller fans  used  by  Professor  Langley  were  6-bladed,  though  in  his 
subsequent  and  highly  successful  aerodrome,  the  twin  propellers 
were  2-bladed  true  screws,  as  were  also  those  of  the  Maxim  machine. 
The  latter  afforded  striking  evidence  of  the  efficiency  of  large-diam- 
eter, slow-speed  propellers. 

Number.  Theoretically,  the  number  of  blades  need  not  be 
considered  at  all.  The  mass  of  air  dealt  with  by  the  propeller  is  rep- 
resented by  a  cylinder  of  indefinite  length,  the  diameter  of  which 
is  the  same  as  that  of  the  screw,  and  the  rate  at  which  this  cylinder 
is  projected  to  the  rear,  depends  theoretically  upon  the  pitch  and 
the  number  of  turns  per  minute  of  the  propeller,  and  not  upon  the 
number  of  blades,  one  or  an  incomplete  helix  being  sufficient,  except 
for  mechanical  reasons.  The  minimum  number  which  can  be  employed 
practically  is,  therefore,  two — and  experience  has  demonstrated 
that  the  same  number  represents  the  practical  maximum  for  an 
aerial  propeller.  The  function  of  the  latter  is  to  create  thrust,  and  to 
do  this,  it  must  force  the  air  to  the  rear  with  the  least  possible  internal 
disturbance,  i.  e.,  it  should  be  thrust  backward  as  a  clean-cut  cylinder, 
and  not  as  a  whirling,  tumbling  mass,  which  would  tend  to  set  up  a 
dragging  wake  and  interfere  with  the  efficiency  of  the  propeller  and 
the  speed  of  the  machine.  Any  number  of  blades  in  excess  of  two 
could  not  operate  in  undisturbed  air  and  would,  in  consequence, 
simply  act  to  churn  the  mass  already  set  in  motion  by  the  others. 
Except  in  case  of  very  small  propellers,  three  blades  are  ordinarily 
employed  in  marine  practice  so  as  to  give  better  mechanical  balance. 

It  may  seem  strange  at  first  sight  that  a  ventilating  fan  should 
operate  most  efficiently  with  a  large  number  of  blades  set  close 
together  and  with  a  fine  pitch,  while  the  opposite  extreme  is  neces- 
sary for  an  aerial  propeller.  Stand  in  the  blast  of  a  big  ventilating 
fan  and  it  appears  to  set  up  a  powerful  current  of  air  which  should 


433 


AERIAL  PROPELLER  13 

represent  the  equivalent  of  considerable  thrust.  It  does,  but  it  must 
be  borne  in  mind  that  a  ventilating  fan  and  a  propeller  are  two 
totally  different  things.  Because  many  blades  are  found  to  be  most 
efficient  in  the  case  of  the  former,  it  is  wholly  wrong  to  assume  that 
the  same  conclusion  holds  good  in  the  case  of  the  latter.  By  increas- 
ing the  number  of  blades,  the  skin  friction  due  to  the  resistance  that 
has  to  be  overcome  in  rotating  the  propeller  through  the  air  is  aug- 
mented. Moreover,  a  fan  is  stationary,  while  a  propeller  is  con- 
stantly advancing  as  well  as  rotating  through  the  air.  The  action 
of  a  fan  blower  is  to  move  a  small  quantity  of  air  at  a  high  velocity, 
whereas  the  action  of  a  propeller  is,  or  should  be,  to  move  a  large 
quantity  of  air  at  a  low  velocity,  since  the  function  of  the  screw  is 
to  create  thrust.  Operating  on  a  yielding  fluid  medium  this  thrust 
will  evidently  be  in  proportion  to  the  mass  of  fluid  moved,  and  also 
to  the  velocity  at  wThich  it  is  put  in  motion.  But  the  power  con- 
sumed in  putting  this  mass  of  air  in  motion  is  proportional  to  the 
extent  of  the  mass  and  to  the  square  of  the  velocity  at  which  it  moves. 
From  this,  it  follows  that  to  obtain  a  given  thrust  with  a  certain 
amount  of  power,  it  is  essential  that  as  large  a  volume  of  air  be 
handled  as  possible  and  that  the  velocity  imparted  to  it  be  as  little 
as  possible.  As  explained  in  connection  with  the  action  of  the  pro- 
peller when  the  aeroplane  is  held  and  when  in  flight,  the  fan  is  designed 
to  create  static  thrust  while  the  propeller  is  designed  to  set  up  dynamic 
thrust.  The  maximum  volume  of  air  must  be  moved  backward  with 
the  least  possible  acceleration.  In  fact,  the  multi-bladed  propeller 
revolving  at  a  hi£h  speed  is  apt  to  set  up  what  is  known  in  marine 
engineering  parlance  as  "cavitation,"  in  which  the  high  speed  of  the 
screw  causes  it  to  carry  round  a  certain  amount  of  the  medium  with 
it,  so  that  the  blades  strike  no  undisturbed  or  solid  air  at  all  with  a 
proportionate  decrease  in  thrust,  or  rather  an  almost  entire  absence 
of  it.  The  propeller  literally  "digs  a  hole  in  the  air"  and  revolves 
in  it  without  pushing  the  aeroplane  ahead. 

It  will  also  be  evident  that  there  is  possible  a  number  of  blade 
arrangements.  Not  only  may  the  blades  differ  in  their  number, 
in  their  outline,  in  their  cross  section,  pitch,  and  angles  of  setting, 
but  they  may  also  differ  in  the  angles  they  make  with  their  plane  of 
rotation,  in  their  longitudinal  placing  on  the  propeller  shaft,  and  in 
the  use  of  longitudinal  sections  from  hub  to  tip  that  are  straight  or 


423 


14  AERIAL   PROPELLER 

curved.  Propeller  blades  in  line,  or  at  right  angles  to  the  shaft, 
are  almost  universal.  The  advantage  of  this  is  that  centrifugal  force 
exerts  a  direct  pull  from  the  hub  without  any  tendency  to  move 
the  blades  longitudinally,  parallel  with  the  axis  of  revolution.  A 
supposed  disadvantage  is  the  escape  of  air  from  the  propeller  tips 
without  aiding  in  propulsion.  But  as  any  such  rapidly  thrown  air 
is  more  apparent  when  the  propeller  is  held  and  is  then  working  as 
a  fan,  than  when  working  in  flight,  it  has  never  been  considered  of 
sufficient  seriousness  to  be  taken  into  consideration. 

Dihedrally-arranged  propeller  blades  with  the  hub  forward, 
either  with  straight  or  curved  blades,  would  utilize  the  air  that  is  apt 
to  escape  at  the  tips,  but  they  would  also  increase  the  amount  of  the 
disturbance,  subjecting  the  air  behind  the  blades  to  direct  centrif- 
ugal action.  Moreover,  this  would  require  very  stiff  blades  or  guy 
wires,  to  prevent  the  blades  from  straightening  out  under  centrifugal 
force,  and  such  wires  would  interpose  additional  resistance  to  rota- 
tion with  a  corresponding  disadvantage. 

Area.  This  violent  disturbance  of  the  air  is  affected  very 
markedly  by  the  area  of  the  blades.  In  marine  engineering,  narrow 
blades  are  usually  employed  on  slow-speed  propellers  where  cavita- 
tion  is  not  a  factor  to  be  guarded  against.  But  in  high-speed  marine 
propellers,  where  it  is  likely  to  occur,  the  projected  area  of  the 
blades  is  sometimes  as  much  as  0.6  of  the  total  disk  area.  In  the 
case  of  aerial  propellers,  cavitation  is  not  likely  to  occur,  particularly 
with  a  2-bladed  propeller,  unless  the  speed  is  very  high — 1,500 
r.  p.  m.  or  more,  so  that  narrow  blades  are  preferable.  Experiments 
in  marine  propulsion  also  show  that  the  thrust  depends  more  upon 
the  disk  area  than  upon  the  width  of  the  blades.  Both  in  marine 
and  aerial  practice,  multiplicity  of  blades,  or  increased  blade  area, 
tends  to  reduce  the  efficiency,  apart  altogether  from  the  questions 
of  weight  and  constructional  difficulties. 

Contour.  It  must  be  borne  in  mind  that  a  propeller  is  nothing  more 
nor  less  than  a  form  of  aeroplane  specially  designed  to  travel  a  helical 
path,  and  that  the  same  laws  govern  it  as  those  pertaining  to  the 
action  of  the  supporting  surfaces  in  striking  and  passing  through  the 
air  which  forms  their  support.  The  blades  should,  therefore,  be 
concave  or  hollow-faced  and  partake  of  the  stream  line  formation,  a 
condition  that  is  not  fulfilled  where  the  face  of  the  blade  is  flat,  such 


424 


AERIAL   PROPELLER  15. 

a  surface  cutting  into  the  air  with  considerable  shock,  and  by  no 
means  creating  as  little  undesirable  motion  in  the  surrounding  medium 
as  possible.  A  curved  face  blade  has  of  necessity  an  increasing  pitch 
from  the  cutting  edge,  or  attacking  face,  to  the  trailing  edge  (con- 
sidering, of  course,  any  particular  section) .  In  such  a  case,  the  pitch 
of  the  propeller  is  its  mean  effective  pitch.  This  question  of  increas- 
ing pitch  with  the  width  of  the  blade,  has  an  important  bearing  on 
the  subject  of  blade  area,  as  to  make  a  wide  hollow-faced  blade 
would  soon  result  in  reaching  an  excessive  angle.  In  the  case  of 
the  flat  blade,  the  same  thing  is  true,  because  by  the  contact  of  its 
molecules  with  the  "initial  minimum  width"  the  air  has  already 
been  accelerated  up  to  its  final  velocity,  and  further  area  is  not  alone 
wasted,  but  is  detrimental  to  efficiency.  Requisite  strength  and 
stiffness,  of  course,  set  a  limit  on  the  final  narrowness  of  the  blades, 
apart  from  other  considerations. 

Flexible  Type.  Reference  has  been  confined  to  propellers  with 
rigid  blades — preferably  of  wood.  There  is  another  type,  known  as 
the  flexible-bladed  propeller,  which  is  so  constructed  as  to  give  a 
self-feathering  action  to  the  blades,  i.e.,  a  self- varying  pitch,  the  air 
resistance  to  rotation  causing  the  blades  to  twist,  and  to  become  of 
less  and  less  pitch  with  increasing  speed.  This  type  has  found  some 
advocates,  or  at  least  it  did  three  or  four  years  ago.  Experiments 
with  it  indicate  a  great  loss  of  power,  so  that  it  is  far  from  efficient. 
A  flexible-bladed  type  of  this  kind  measuring  .19  inches  in  diameter 
and  having  three  blades  showed  on  test  a  thrust  of  only  3  ounces 
at  480  r.  p.  m.  The  power  was  estimated  at  about  -* -horse-power, 
which  would  give  a  result  of  1  pound  thrust  per  horse-power,  so  that 
it  seems  hardly  worth  while  to  experiment  further  with  this  type. 

Fabric-Covered.  Another  form  of  propeller  that  has  been  used 
consists  of  a  frame,  over  which  canvas  is  stretched  taut  to  form  the 
blades,  but  the  fabric  does  not  remain  taut  when  the  propeller  is 
revolving  at  a  high  speed.  It  is,  moreover,  difficult  to  make  any- 
thing but  a  flat-bladed  propeller  in  this  form  and  have  it  sufficiently 
rigid.  Such  propellers  were  employed  on  some  of  the  early  French 
dirigibles,  mainly  on  account  of  their  lightness,  but  they  did  not  prove 
practical. 

Another  disadvantage  of  these  fabric  propellers  was  the  fact 
that  the  blades  consisted  of  only  comparatively  small,  isolated  sur- 


425 


16  AERIAL   PROPELLER 

faces  at  the  outer  ends  of  the  supporting  arms,  and  this  fault  was 
repeated  in  some  of  the  metal  propellers  employed  abroad.  This 
has  been  done  on  the  ground  that  the  part  of  the  blade  near  the  hub 
adds  little  or  nothing  to  the  effective  thrust  of  the  propeller.  While 
this  is  undoubtedly  true,  every  part  of  the  blade,  except  where  it 
actually  loses  its  curvature  to  become  part  of  the  hub,  exerts  its 
proportionate  amount  of  propulsive  power,  whereas  in  the  other 
type,  resembling  a  double  canoe  paddle,  the  cut  away  part  merely 
adds  to  the  air  resistance  of  the  machine  as  a  whole,  and  the  efficiency 
of  the  screw  itself  is  reduced  proportionately.  Variable  pitch  pro- 
pellers for  aeroplanes  have  again  been  taken  up  in  France  notably 
by  Brequet  and  Antoinette,  but  the  blades  have  been  of  wood  or 
metal,  mounted  so  as  to  permit  of  partially  revolving  on  their  own 
axis,  this  movement  being  controlled  by  springs. 

Speaking  of  efficiency,  it  will  be  noted  that  the  best  results 
obtained  by  some  of  the  earlier  experimenters  were  not  very  high.  The 
thrust  per  brake  horse-power  obtained  by  Langley  was  7  pounds, 
by  Maxim  9  pounds,  by  Spencer,  using  a  Maxim-type  propeller, 
6  pounds,  by  Farman  and  a  number  of  other  French  experimenters, 
between  G  and  7  pounds.  These  figures  have  not  been  improved 
upon  to  any  great  extent,  except  in  isolated  cases,  up  to  the  present 
day,  so  that  it  will  be  apparent  that  the  aerial  propeller  is  lamentably 
inefficient,  and  that  most  of  the  recent  successes  have  obtained  in 
spite  of  its  shortcomings,  rather  than  otherwise.  The  cost  of  this 
is  redundant  power  and  weight,  since  the  propellers  waste  a  very 
substantial  fraction  of  the  energy  supplied  by  the  motor.  This 
extravagant  provision  of  excess  power  that  is  necessary  likewise 
involves  a  larger,  stronger,  and  heavier  machine  as  a  whole,  for  a 
given  passenger-carrying  capacity. 

Propeller  Construction.  Material  In  actual  propeller  construc- 
tion various  expedients  have  been  tried  by  the  French  and  while 
some  of  these  propellers  have  been  ingenious,  the  example  thus  set 
has  not  been  generally  followed.  The  Antoinette  is  one  of  the  very 
few  machines,  if  not  the  only  one,  that  employs  a  metal  propeller. 
Bleriot  experimented  with  metal  propellers  in  the  early  days  but 
shortly  abandoned  them  for  wood,  which  he  has  since  adhered  to. 
The  Antoinette  propeller  has  a  diameter  of  7  feet  2  inches  and  a 
pitch  of  4  feet  3  inches.  It  is  composed  of  a  stiff  steel  tube  to  which 


426 


AERIAL  PROPELLER  17 

are  attached  two  blades  of  sheet  aluminum  riveted  to  it.  The  blades 
themselves,  however,  are  adjustable,  thus  permitting  of  varying  the 
pitch.  It  is  designed  to  run  at  1,100  r.  p.  m.  The  Vendome  is  a 
hollow  two-bladed  propeller,  8  feet  in  diameter,which  is  built  of  hickory 
veneer,  mounted  on  canvas,  so  that  despite  its  size,  it  weighs  only 
4.4  pounds.  While  this  represents  exquisite  workmanship  and  a 
beautiful  finish,  an  extremely  light  weight  is  no  advantage,  particu- 
larly where  the  propeller  is  relied  upon  to  act  as  a  substitute  for  the 
flywheel  of  the  motor,  as  is  generally  the  case.  The  Tatin,  another 
French  example,  is  a  two-bladed  propeller  built  up  of  laminated 
wood,  and  represents  one  of  the  rare  instances  in  which  the  design 
calls  for  a  pitch  exceeding  the  diameter.  The  latter  is  7  feet  8  inches, 
while  the  pitch  is  8  feet  2  inches,  the  propeller  being  designed  to 


Fig.  6.     Method  of  Fitting  Blocks  from  Which  Propeller  is  Shaped 

run  at  700  r.  p.  m.,  being  driven  through  a  reducing  gear.  Its  con- 
struction is  peculiar  in  that  instead  of  being  built  up  by  simply 
gluing  one  board  over  another,  a  number  of  thin  superimposed  sheets 
or  laminations  of  wood  are  let  into  framing,  the  whole  being  covered 
tightly  with  Japanese  silk  and  then  varnished. 

Standard  Construction.  The  standard  method  of  propeller  con- 
struction, in  that  it  is  now  most  generally  followed,  is  that  of  gluing 
a  number  of  boards  together  under  heavy  pressure  and  then  prac- 
tically whittling  the  propeller  out  of  the  block  thus  formed,  Fig.  6. 
Wood  is  preferred  to  steel  for  a  number  of  reasons,  chief  among 
which  is  the  liability  of  a  steel  blade  to  snap  suddenly  and  without 
warning  under  the  influence  of  temperature  changes  or  violent 
shocks.  If  sufficiently  strong,  a  wood  blade  is  less  liable  to  snap, 


427 


18  AERIAL   PROPELLER 

and  gives  warning  of  impending  fracture  by  bending  and  splitting. 
Wood  propellers  are  also  much  lighter  than  those  of  steel.  The  blade 
of  an  aerial  propeller  has  sharp  edges,  particularly  on  what  is  termed 
the  "attacking  edge,"  but  it  is  quite  thick  along  its  median  line. 
It  is  made  thick,  not  merely  to  strengthen  it,  but  because  thickness 
offers  the  same  aerodynamic  advantage  in  the  propeller  that  it 
presents  in  the  sustaining  surfaces  of  the  aeroplane.  This  thickness 
gives  ample  strength  when  the  material  is  wood,  while  it  would  make 
a  steel  propeller  unnecessarily  strong  and  excessively  heavy,  though, 
for  that  matter,  it  would  be  possible  to  employ  sheet-steel  stampings 
or  pressed  steel,  autogenously  welded  together.  In  this  case,  the 
expense  for  dies  would  be  prohibitive  unless  propeller  designs  were 
standardized,  so  that  wood  has  the  advantage  of  being  much  easier 
to  work  than  steel. 

Chauviere  Method.  The  Chauviere  propellers,  used  on  most 
French  machines,  are  built  up  of  several  planks  of  well  seasoned 
ash  or  walnut.  These  planks  are  cut  to  the  shape  of  a  number  of 
sections  transverse  to  the  axis  of  a  propeller  designed  in  accordance 
with  the  special  conditions  proposed,  such  as  the  r.  p.  m.  rate  at  which 
it  is  to  turn,  torque,  tractive  effect,  and  the  speed  for  which  the 
aeroplane  itself  is  designed.  Each  plank  forms  part  of  both  blades 
of  the  2-bladed  propeller  and  therefore  a  hole  is  cut  into  the  center 
to  receive  the  hub.  The  planks  are  then  glued  together  on  their 
faces,  after  having  been  accurately  centered  and  orientated,  so  that 
they  represent  the  form  of  the  finished  propeller  approximately 
and  show  some  of  its  lines  accurately.  The  next  operation  con- 
sists of  removing  the  superfluous  wood  between  these  lines  and 
working  the  entire  surface  to  the  required  form.  This  is  a  delicate 
task  requiring  great  skill  and  care,  for  the  removal  of  too  much  material 
at  any  point  would  ruin  the  work.  The  surface  is  finished  by  polishing. 

A  still  more  delicate  operation  is  necessary  to  balance  the  blades, 
as  even  a  slight  difference  in  length,  weight,  or  shape  might  set  up 
dangerous  vibrations  in  a  rapidly  revolving  propeller.  The  pro- 
peller is  mounted  on  a  mandrel,  which  is  poised  on  very  sensitive 
friction  wheels  in  a  specially-devised  machine,  and  the  blades  are 
carefully  retouched  until  the  propeller  remains  in  equilibrium  in 
every  position.  It  is  then  coated  with  special  varnish  to  give  it  a 
smooth  surface  and  to  protect  it  from  the  weather.  The  finished 


428 


AERIAL   PROPELLER  19 

propeller  is  firmly  attached  to  the  shaft  by  clamping  its  central  por- 
tion between  two  steel  disks,  connected  by  bolts  passing  through  the 
wood  of  the  hub. 

American  Methods.  Two  methods  are  in  vogue  in  this 
country  at  present.  In  one,  the  planks  forming  the  propeller  are 
offset  upon  one  another  in  such  a  manner  that  when  the  superfluous 
wood  represented  by  their  protruding  edges  is  removed,  the  surface 
thus  obtained  is  the  curvature  desired  in  the  finished  propeller.  The 
planks  must,  accordingly,  be  finished  very  accurately  before  gluing 
and  must  be  put  together  very  accurately  to  insure  this  result.  The 
other  method,  which  is  that  mentioned  in  the  article  on  "  Build- 
ing a  Curtiss  biplane/'  and  illustrated  therein,  Fig.  21,  is  merely 
to  glue  the  planks  together  in  such  a  manner  that  sufficient  excess 
material  is  allowed,  back  and  front,  to  whittle  the  resulting  block 
down  to  the  required  dimensions  and  shape.  Templates,  represent- 
ing the  curvature  of  the  back  and  front  at  sections  3  inches  apart 
from  the  hub  right  out  to  the  tip,  are  employed  to  note  the  accuracy 
of  the  work  as  it  proceeds.  The  greatest  care  must  naturally  be 
employed  not  to  cut  too  deep  at  any  point.  In  either  case,  the  finish 
is  the  same — rubbing  smooth,  polishing,  and  varnishing.  Ever 
since  the  accident  to  the  propeller  of  the  Wright  machine  in  which 
Lieutenant  Selfridge  was  killed  at  the  United  States  Army  accept- 
ance tests  in  1908,  it  has  become  customary  to  protect  the  tips  of 
wood  propellers  by  covering  them  for  a  foot  or  more  from  their  ends 
with  cheese  cloth,  or  other  light  fabric.  This  cloth  is  stretched  on 
very  tight,  like  a  pocket  covering  the  end  of  the  tip,  and  is  glued 
down  and  varnished,  so  that  it  practically  becomes  a  part  of  the  wood 
and  there  is  no  break  in  the  surface.  Some  such  protection  is  neces- 
sary to  prevent  splintering  when  accidentally  striking  objects, 
particularly  \vhen  on  the  ground,  as  the  propeller  tips  are  very  thin 
and  correspondingly  fragile. 

The  method  of  gluing  the  planks  together  in  fan  shape  so  that 
the  points  at  which  the  planks  overlap  will  practically  mark  the  line 
of  curvature  of  the  finished  blade,  is  that  followed  in  the  making  of 
the  Wright  propellers.  Contrary  to  the  custom  of  employing  ash, 
maple,  walnut,  and  other  hard  woods,  or  alternate  laminations  of 
these  with  spruce,  the  Wright  Brothers  pin  their  faith  to  spruce 
alone,  as  is  the  case  in  the  construction  of  the  entire  framing  of 


429 


20  AERIAL   PROPELLER 

their  machine,  with  the  exception  of  the  bed  for  the  motor.  The 
Wright  propeller  is  built  up  of  three  planks  glued  together  as  shown 
in  Fig.  6,  so  that  they  overlap  like  the  sticks  of  a  fan  to  an  extent 
which  diminishes  as  the  distance  from  the  axis  increases.  The  super- 
fluous parts  of  the  wood  represented  by  the  dark  and  triangular  areas 
of  the  upper  diagrams  in  the  figure,  are  then  cut  away,  the  curvature 
being  tested  at  every  point  with  the  aid  of  templates  as  the  work 
proceeds.  In  contrast  with  this,  Chauviere  propellers  are  made  from 
six  or  seven  overlapping  planks.  The  finished  propeller  contains  only 
about  8|  per  cent  of  the  wood  of  the  original  planks.  A  study  of 
the  sections,  A,  B,  and  C  in  Fig.  6  will  make  clear  both  the  pro- 
gressive variation  in  slope  and  the  curvature  from  the  axis  to  the 
periphery,  and  the  corresponding  variation  in  the  thickness  of  the 
blade.  The  general  direction  of  these  sections  will  be  more  or  less 
inclined  to  the  axis  of  the  propeller  according  to  their  distance  from 
it.  In  the  making  of  metal  propellers,  the  blades  are  usually  riveted 
to  the  arms,  composed  of  steel  tubes  brazed  into  the  hub.  The 
blades  themselves  are  then  given  the  proper  curvature  by  hammer- 
ing upon  a  form.  Casting  in  the  form  desired  and  twisting  into 
shape  have  both  been  tried,  but  without  much  success,  very  few 
metal  propellers  of  any  kind  being  in  use  today. 

Hollands.  A  recent  British  patent  on  an  all-steel  propeller  is  of 
interest.  It  is  known  as  the  Hollands  propeller  and  is  formed  of 
thin  steel  plates,  brazed  together  at  their  edges.  In  cross  section  the 
blades  are  of  shell-like  form  concave  on  the  driving  side  and  convex 
on  the  leading  surface,  the  concavity  being  less  than  the  convexity. 
The  greatest  depth  of  concavity  equals  one-eighteenth  of  the  width 
of  the  blade,  and  is  situated  at  one-third  of  the  breadth  from  the 
leading  edge  throughout  the  length  of  the  blade.  The  blades  taper 
from  root  to  tip  and  are  set  at  a  gradually  decreasing  pitch  angle, 
being  15  degrees  at  the  tip  and  30  degrees  midway  the  length  of  the 
blade.  An  efficiency  of  85  per  cent  is  claimed  for  it  on  the  ground  that 
it  has  a  minimum  radius  of  centers  of  pressure  and  mass,  resulting 
in  minimum  torque  in  relation  to  thrust,  or  greatest  thrust  for  a  given 
turning  moment,  least  centrifugal  stress  for  a  given  angular  velocity 
and  diameter,  and  the  least  bending  moment  on  the  blades. 

Propeller  Design.  True-Screw  Type.  There  are  two  forms  of 
propellers  extant,  the  true-screw  and  the  variable-pitch,  the  former 


430 


AERIAL  PROPELLER  21 

being  very  largely  in  the  majority,  in  fact,  used  almost  altogether, 
although  the  variable-pitch  type  likewise  has  its  advocates.  The 
effect  of  revolving  an  aerial  propeller,  as  already  explained,  is  to 
create  a  column  or  shaft  of  air  out  of  the  body  of  air  in  which  it  is 
run,  of  a  diameter  nearly  corresponding  to  the  diameter  of  the  pro- 
peller, the  column  being  given,  by  the  pitch  and  rotation  of  the  blades, 
a  backward  motion  proportionate  to  the  power  delivered  to  the  pro- 
peller, the  movement  of  the  latter  being  similar  to  that  of  a  nut 
when  being  moved  along  a  bolt  in  the  operation  of  loosening.  The 
underlying  principle  of  the  screw  thus  being  necessary,  it  is  essential 
that  the  propeller,  which  is  the  column-forming  instrument,  should 
be  true  to  work  with  the  greatest  efficiency;  it  should  run  through 
the  column  within  the  main  body  in  the  same  way  that  a  well-made 
nut  worms  its  course  along  a  well-made  bolt.  Each  part  of  the  bolt- 
engaging  surface  of  the  nut  must  engage  with  the  surface  of  the 
"fluid-bolt"  it  creates,  with  equal  pressure  throughout  the  whole  of 
its  convolutions.  Any  distortion  or  lack  of  trueness  in  the  thread 
of  an  ordinary  nut  will  effectually  spoil  its  bolt  by  stripping  the 
thread  to  some  degree,  in  other  words,  ruining  its  engaging  surface 
while  coincidently  taking  a  uselessly  large  amount  of  power  to  force 
it  along  the  bolt.  The  same  principle  applies  in  the  case  of  the  pro- 
peller, and  if  the  blades  are  distorted,  rough,  or  untrue,  they  will  act 
in  the  same  manner  as  the  badly-made  nut  and  waste  a  great  deal  of 
the  power  exerted  in  driving. 

On  the  true-screw  principle,  the  effect  of  the  propeller  in  the 
air  must  start  from  the  point  where  the  blade  springs  from  the  hub 
and  continue  right  through  its  entire  length  and  surface.  Each 
blade  must  accurately  match  its  counterpart  and  be  fixed  in  relation 
to  it  so  that  at  no  point  will  one  part  of  the  propeller  try  to  climb 
through  more  air,  or  worm  through  any  more  or  less  of  its  true  course, 
than  it  should.  If  not  properly  and  accurately  made,  instead  of 
thrusting  backward  a  clean-cut  column  of  air,  it  will  simply  churn 
and  worry  it  with  a  great  loss  of  power.  But  a  propeller  which  is 
true  screw  in  shape,  may  be  very  untrue  in  its  action  on  the  air. 
To  be  efficient,  it  must  act  as  a  whole  upon  the  air,  as  a  true  screw 
nut  does  upon  its  bolt.  In  other  words,  the  best  propeller  for  any 
particular  case  may  have  greater  or  less  angularity  of  its  blade  at 
various  places,  than  would  be  called  for  if  the  propeller  were  designed 


431 


22 


AERIAL  PROPELLER 


to  be  a  true-screw  shape  for  the  particular  pitch  speed  required.  In 
any  case,  it  must  be  a  true  screw  in  its  operation.  As  mentioned  in 
connection  with  the  details  of  building  a  Curtiss  biplane,  the  num- 
ber of  aeroplane  designers  competent  to  build  a  properly-made 
variable-pitch  propeller  is  very  small  indeed,  which  probably  accounts 
for  the  small  number  in  use.  Moreover,  the  advantages  claimed  for 
it  appear  to  be  so  largely  based  upon  theory  as  to  provide  small 
incentive  for  its  adoption. 

Some  idea  of  the  dynamics  of  the  action  of  the  aerial  propeller 
may  be  gained  by  citing  a  very  simple  illustration.  Take  the  case 
of  a  smoker  "blowing  rings."  It  will  be  noted  that  a  cylinder  of 
air  is  propelled  from  the  mouth  into  the  still  air  of  the  room.  At 
the  edge  of  this  cylinder  of  air  is  the  smoke  ring,  and  it  will  be  evident 
that  it  revolves  within  itself,  the  inside  traveling  forward  and  the 

outside  of  the  ring  to  the  rear. 
This  is  obviously  due  to  the 
friction  between  the  moving 
cylinder  of  air  and  the  still 
air  through  which  it  travels. 
This  action  is  more  markedly 
apparent  in  the  smoke  rings 
that  issue  from  saluting  guns 
X  and  from  locomotive  stacks 

Fig.  7.    DiaeramShowins  Action  of  Propeller  Blades    "nder  favorable  atmospheric 

conditions,  but  equally  effec- 
tive results  may  be  obtained  with  a  "smoke  ring  box,"  made  from  an 
ordinary  stationery  box  with  a  circular  hole  cut  out  of  the  center  of  the 
cover.  Fill  this  with  smoke  and  tap  lightly,  to  compress  the  air  within, 
and  a  ring  will  be  emitted.  A  hard  tap  will  cause  a  clear,  sharp  ring 
to  shoot  rapidly  upward,  but  by  raising  the  box  cover  slightly  and 
gently  lowering  it,  a  series  of  rings  will  emerge  and  float  slowly  up, 
affording  sufficient  opportunity  to  study  their  evolutions  closely. 
In  any  case,  when  a  smoke  ring  is  produced,  its  center  is  very  small 
and  grows  larger  as  the  ring  expands.  It  is  with  the  first  stage  of  the 
ring  that  we  will  deal. 

Assume  the  two  cross-hatched  ellipses  of  Fig.  7  to  show  the 
section  of  a  smoke  ring,  cut  through  its  center.  The  ring,  acted  upon 
by  a  force  in  the  direction  of  D,  revolves  within  itself  as  shown  by 


432 


AERIAL   PROPELLER  23 

the  arrows.  Friction  with  the  outside  air  mass  causes  this  rotation 
and  reduces  the  velocity  of  the  extreme  edge  of  the  ring  to  zero,  as 
shown  at  A  and  A'.  This  ring  then  apparently  rolls  inside  a  tube  of 
air,  and  as  its  maximum  velocity  is  at  C  and  C",  the  points  B  and  E' 
must  attain  a  velocity  equal  to  one-half  that  at  C  and  C'.  The 
portion  between  C  and  C'  forms  the  shank  and  hub  in  most  pro- 
pellers and  does  not  assist  materially  in  propulsion,  if  at  all.  The 
above  may  be  taken  as  the  relative  velocities  of  various  portions  of 
the  disk  of  the  air  column  sheared  loose  by  the  slip  of  a  screw-pitch 
propeller  while  traveling  through  the  air  at  its  normal  speed. 

Variable-Pitch  Type.  Taking  a  screw-pitch  propeller,  blade  inci- 
dence angles  (blade  angles  not  corrected  for  slip)  are  found  at  the 
different  radii  corresponding  to  Fig.  7,  to  be  as  follows:  At  C  and  C", 
14  degrees;  at  B  and  B' ',  7  degrees;  and  at  A  and  A',  3J  degrees.  Now 
the  velocity  at  C  and  Cf  is  twice  as  great  as  at  B  and  Bf.  In  order, 
therefore,  to  raise  the  velocity  at  B  and  B'  to  that  at  C  and  C',  we 
must  increase  the  blade  angle  of  the  propeller  as  much  again,  or  from 
7  to  14  degrees.  The  velocity  at  A  and  A'  being  practically  zero,  it 
will  be  necessary  to  increase  the  blade  angle  considerably  at  this 
radius.  Doubling  the  blade  angle  at  B  and  B'  has  doubled  the 
velocity  at  this  point;  hence,  increasing  the  blade  angle  at  A  and  A' 
(3J  degrees)  to  the  former  angle  of  B  and  B'  (7  degrees),  should  give 
this  radius  the  former  B  and  B'  velocity,  or  one-half  that  of  C  and  C". 
By  doubling  this  angle,  i.  e.,  increasing  it  to  14  degrees,  we  again 
reach  the  velocity  of  C  and  C' '. 

These  angles  may  then  be  assumed  to  give  a  slip  column  of  air  of 
uniform  velocity,  and  as  such  a  column  of  air  is  what  the  propeller 
pushes  against,  the  slip  column  would  give  a  more  efficient  back- 
ground for  propeller  purchase,  so  to  speak,  than  the  varied  velocity 
column  delivered  by  the  screw-pitch  propeller.  This  constitutes  an 
argument  for  the  uniform  pitch  propeller,  it  being  noticeable  that  the 
products  of  increasing  and  doubling  the  various  angles  result  in  each 
case  in  the  same  angle,  namely,  14  degrees.  Correcting  this  angle 
throughout  its  length  in  order  that  the  theoretical  and  practical  foot 
pitch  may  agree,  add,  say,  2 \  degrees,  and  the  result  will  be  a  uniform 
or  straight-pitch  propeller,  with  a  blade  angle  of  16J  degrees. 

From  what  has  been  said  thus  far,  it  will  be  apparent  that  there 
is  considerable  diversity  of  opinion  regarding  the  design  of  the  pro- 


433 


24  AERIAL   PROPELLER 

peller,  and  likewise  a  lamentable  lack  of  definite  knowledge  regard- 
ing propeller  efficiencies.  Since  errors  in  the  design  may  necessitate 
a  motor  of  30  to  100  per  cent  more  power  to  attain  the  desired  result, 
the  importance  of  working  along  well-settled  lines  will  be  manifest. 
Problems  in  Design.  The  salient  points  of  design  already  dwelt 
upon,  putting  them  in  the  form  of  questions  which  must  be  answered 
by  the  designer  when  planning  his  propeller,  are  as  follows: 

1.  At  what  speed  should  the  propeller  be  revolved  to  give  a 
certain  thrust? 

2.  What  combination  of  pitch  and  number  of  turns  per  minute 
would  produce  the  maximum  thrust  with  the  minimum  power? 

3.  Is  it  better  to  use  a  fine  pitch  and  revolve  the  screw  fast? 

4.  Or  is  it  better  to  use  a  coarse  pitch  and  turn  the  screw  slowly? 

5.  Are  wide  or  narrow  blades  preferable? 

6.  Should  the  blades  have  a  uniform  or  an  increasing  (variable) 
pitch? 

7.  Which  is  preferable  to  use,  two,  three,  four,  or  more  blades? 

8.  Given  two  screws  exactly  alike,  but  one  with  two  or  three 
times  the  diameter  of  the  other,  how  much  more  thrust  should  the 
larger  one  give  than  the  smaller  when  revolved  at  the  same  speed? 

9.  How  much  more  power  is  required  to  obtain  a  given  number 
of  pounds  thrust  while  traveling  at  20,  30,  or  40  miles  an  hour,  than 
to  give  the  same  thrust  when  standing  still? 

10.  What  percentage  of  the  power  used  is  due  to  skin  friction? 

Propeller  Tests.  Herring.  To  obtain  propeller  data,  Herring, 
long  associated  with  Curtiss,  devised  the  apparatus  shown  in  Fig.  8'. 
On  this  a  great  many  propellers  have  been  tested,  both  in  still  air 
^and  in  a  powerful  blast  of  definitely  known  velocity,  to  simulate 
the  condition  of  traveling  through  the  air.  M  represents  a  variable- 
speed  electric  motor  of  5  horse-power.  This  is  rigidly  mounted 
on  a  table,  and  by  means  of  resistances  and  a  controller,  may  be 
kept  running  steadily  at  any  speed  desired  between  700  and  1,500 
r.  p.  m.  The  propeller  to  be  tested,  V  is  mounted  on  a  shaft  T  on 
which  is  mounted  a  pulley  P.  This  shaft  runs  in  ball  bearings  W 
and  U,  and  is  held  in  place  in  the  room  by  six  wires  II',  H" ,  etc. 
These  suspended  wires  have  turnbuckles  inserted  in  them  for  the 
purpose  of  adjustment,  and  very  stiff  springs  for  taking  up  the 
vibration  at  high  speeds.  An  endless  belt  connects  the  motor  pulley 


434 


AERIAL   PROPELLER 


25 


R  with  the  pulley  P  on  the  propeller  shaft.  This  belt  passes  under 
the  ball-bearing,  mounted  pulleys  N  and  0,  which  have  suspended 
from  them  the  equal  weights  C  and  D,  for  the  purpose  of  keeping 
the  belt  taut.  In  testing,  the  speed  at  which  the  propeller  is  turning 
is  measured  at  W  where  the  shaft  projects  through  the  bearing. 

The  amount  of  powrer  in  foot  pounds  per  minute  used  in  driv- 
ing the  screw,  is  the  pull  on  the  belt  multiplied  by  its  speed.  Or, 
to  be  more  exact,  it  is  the  pull  on  the  belt  multiplied  by  the  number 
of  turns  of  the  pulley  P  per  minute,  multiplied  by  the  circumference 
of  this  pulley  in  feet.  The  circumference  of  P  can  be  directly  meas- 
ured, while  the  pull  on  the  belt  is  always  exactly  half  the  reading  of 


SCALES  FOR  MEASUR     '. 

fNG  PVLL  OR  BELT 


: 


M 


Fig.  8.      Herring's  Apparatus  for  Testing  Propeller  Thrusts  and  Amount  of 
Power  Developed 

the  scale  B.  The  thrust  of  the  screw  is 'measured  direct  by  means 
of  the  scale  A,  which  is  connected  by  a  wire  with  the  bearing  U. 
A  stop  S  prevents  the  shaft  T  from  moving  back  beyond  a  certain 
point.  An  electric  contact  E  and  the  lamp  L  show  when  the  pro- 
peller pulls  enough  to  move  the  bearing  away  from  S. 

The  turnbuckle  G'  is  used  for  adjusting  the  force  with  which  the 
propeller  axle  is  held  against  the  stop  S,  which  force  must  be  overcome 
before  the  lamp  L  glows.  This  force — the  actual  thrust  of  the  screw 
—is  measured  direct  on  the  scale  A. 

Screws  ranging  from  7  inches  tb  4  feet  in  diameter  were  tested 
at  some  15  to  20  ranges  of  speed  each,  and  screws  with  wide  and 


435 


26  AERIAL   PROPELLER 

also  narrow  blades,  but  of  the  same  diameter  and  pitch,  were  tried. 
Also  screws  of  the  same  number  and  width  of  blades,  differing  only 
in  pitch,  were  tried.  A  screw  of  40-inches  diameter  and  having  no 
pitch  was  also  tested  at  many  speeds  to  determine  the  power  absorbed 
in  skin  friction.  As  the  apparatus  was  built  with  extreme  care  and 
fine  ball  bearings  were  used  throughout,  its  friction  was  found  to  be 
surprisingly  small — so  small  in  fact,  that  even  in  the  experiment 
on  skin  friction,  the  forces  could  be  measured  with  accuracy.  Inci- 
dentally, the  reduction  of  the  thrusts  of  the  various  screws  caused  by 
wind  pressure  against  the  pulley  P  was  arrived  at  with  considerable 
accuracy  by  substituting  pulleys  of  different  diameters,  and  noting 
the  change  in  the  thrust  of  the  screws  when  running  at  the  same 
speed. 

To  obtain  an  idea  of  the  relative  values  of  different  designs  of 
screws  under  conditions  of  actual  practice,  a  second  motor  which 
does  not  appear  in  the  drawing,  was  mounted  in  front  of  W.  A 
propeller  was  mounted  direct  on  the  shaft  of  this  second  motor, 
and  made  to  furnish  a  blast  in  which  the  screw  being  tested  worked. 
As  the  second  motor  also  could  be  driven  at  any  desired  speed,  and 
the  blast  from  it  accurately  measured,  the  screws  were  tested  under 
conditions  which  closely  approached  those  to  be  expected  in  practice, 
when  the  aeroplane  is  moving  through  the  air  in  flight. 

The  results  embraced  some  900  or  more  readings  and  showed  in 
a  striking  manner  that  comparatively  slight  differences  in  design 
may  easily  mean  great  saving  or  waste  of  power.  By  placing  an 
obstruction  in  front  of  the  propeller  when  it  was  revolving  in  still 
air,  more  thrust  was  obtained  than  was  theoretically  possible.  Block- 
ing the  flow  of  air  at  the  side  of  the  propeller  had  a  tendency  to 
diminish  the  thrust. 

While  this  testing  apparatus  more  or  less  approximates  con- 
ditions of  practice,  it  is  evident  that  a  uniform  blast  of  wind  is  far 
from  representing  the  actual  condition  under  which  a  propeller  has 
to  work,  so  it  would  seem  that  the  only  conclusive  test  of  a  propeller 
is  to  try  out  the  screw  itself  under  practical  flight  conditions.  But 
this  may  be  a  risky  undertaking,  either  in  a  dirigible  or  an  aero- 
plane, and  more  particularly  the  latter,  as  through  some  error  in 
design,  it  may  fall  so  far  short  of  calculations  as  to  be  a  menace  to 
the  safety  of  the  aviator. 


436 


AERIAL   PROPELLER  27 

British  Tests.  The  English  firm,  Vickers  Sons  &  Maxim,  who 
were  responsible  for  the  construction  of  the  huge  British  naval 
dirigible,  have  gone  to  great  expense  to  build  a  testing  apparatus 
for  this  purpose.  It  consists  of  a  great  whirling  table.  From  a  high 
tower  of  steel  erected  on  a  hill  at  an  open  place,  is  hung  a  big  canti- 
lever. The  arm  on  which  the  propeller  is  mounted  is  110  feet  long, 
and  is  balanced  by  an  arm  56  feet  long  and  carrying  a  water-ballast 
tank  at  its  outer  end.  Both  arms  are  built  up  of  steel  angles  and 
are  tied  by  steel  rods  to  a  bracket  at  the  top  of  the  tubular  tower. 
At  the  head  is  a  large  ball  bearing  which  supports  the  entire  weight 
of  the  moving  part  of  the  structure,  while  a  guide  for  the  bottom 
end  is  supplied  with  four  horizontal  rollers  carried  on  cast-iron 
brackets  bolted  to  the  lower  end  of  the  steel  tube  and  rolling  on  a 
turned  track  on  the  collar. 

For  the  motive  power,  there  is  a  100-horse-power  engine  situated 
in  a  cabin  built  round  the  tower  on  the  revolving  arms.  A  line  of 
shafting  carries  the  power  to  the  extremity  of  the  propeller  testing 
arm  and  drives  the  propeller  through  bevel  gearing.  The  propeller 
is  mounted  on  a  sliding  shaft  which  works  against  a  spring  thrust 
abutment.  To  reproduce  actual  working  conditions  more  thoroughly, 
a  car  is  rigged  up,  and  resistance  can  be  put  upon  the  arm  to  vary 
the  speed  at  which  it  rotates.  This  motion  of  the  arm  is  due  entirely 
to  the  propeller  thrust,  and  this  thrust  can  be  measured  accurately 
to  within  1  per  cent,  a  special  device  being  introduced  to  compensate 
for  the  circular  flight  path.  Although  one  of  the  reasons  for  the 
erection  of  this  monster  propeller  testing  plant  has  been  to  promote 
the  trials  of  the  new  screws  for  the  naval  dirigible,  it  is  also  employed 
for  other  tests  and  is  open  to  British  military  and  various  experi- 
menters. 

Number  of  Propellers.  The  number  of  propellers  and  their  loca- 
tion on  the  aeroplane  are  also  considerations  of  importance  which  form 
part  of  the  problem  of  propulsion.  The  chief  reason  for  urging  the 
use  of  plural  propellers  is  to  overcome  the  unbalancing  brought 
about  by  the  gyroscopic  effects  and  those  of  reaction,  it  being  evi- 
dent that  they  can  be  readily  neutralized  by  the  use  of  two  or  more 
propellers  of  the  same  size,  symmetrically  placed  and  revolving  in 
opposite  directions.  That  such  effects  exist  can  not  be  denied, 
but  the  prevailing  opinion  is  that  their  magnitude  with  propellers 


437 


28  AERIAL   PROPELLER 

ranging  from  5  to  10  feet  in  diameter  and  weighing  from  3  to  20 
pounds,  with  a  large  proportion  of  this  weight  in  the  hub,  is  too 
trifling  to  be  seriously  regarded — a  view  that  is  apparently  upheld 
by  the  fact  that  the  Wright  and  Cody  biplanes  are  the  only  suc- 
cessful twin-screw  machines  of  large  size,  i.e.,  not  flying  models. 
This  system  was  first  seriously  applied  by  Maxim  to  his  huge  multiple- 
plane  machine  and  was  subsequently  employed  by  Langley  on  his 
flying  models.  It  certainly  appears  logical  that  a  narrow  propeller 
blade  from  2  to  5  feet  long,  moving  at  high  speed  on  one  side  of  an 
aeroplane,  can  not  produce  any  considerable  reaction  per  unit  of 
area  against  a  broad  wing  surface  on  the  opposite  side,  from  10  to 
25  feet  long. 

For  instance,  take  Bleriot's  cross-channel  machine.  In  this  the 
propeller  blades  are  3 f  feet  long  and  the  wing  span  25  feet.  The  most 
effective  speed  of  this  propeller  is  about  1,200  r.  p.  m.  at  which  about 
25  horse-power  is  required.  This  amount  of  power  is  equivalent  to 
825,000  foot  pounds  a  minute,  or  688  foot  pounds  a  propeller  revolu- 
tion, meaning  that  the  two  propeller  blades  encounter  a  maximum 
possible  resistance  to  their  rotation  of  088  divided  by  21,  the  approxi- 
mate surface  in  square  feet  of  the  propeller  circle  or  disk.  This  gives 
an  approximate  resistance  of  33  pounds,  figured  at  the  propeller  tips, 
which,  extended  to  the  wing  tips,  is  the  equivalent  of  a  trifle  over 
8  pounds  load  on  the  one  wing  end,  raising  the  weight  supported  per 
square  foot  of  area  an  average  of  one  and  two-thirds  ounces  higher  on 
one  wing  than  on  the  other.  Assuming  a  normal  load  of  75  ounces 
to  the  square  foot,  which  is  very  close  to  the  actual,  the  addition 
of  this  amount  unbalances  the  machine  to  the  extent  that  the 
weight  is  only  2  per  cent  more  on  one  side  than  on  the  other. 

Wilbur  Wright  asserts  that  the  Wright  machine  can  be  flown 
with  50  pounds  of  unbalanced  weight,  and  Santos-Dumont  has  flown 
with  40  pounds  on  one  side  of  the  body  of  his  monoplane,  nothing 
more  than  a  slightly  increased  warping  of  the  wings  on  one  side 
being  necessary  to  correct  the  balance,  from  which  it  will  be  apparent 
that  the  unbalanced  reaction  from  a  single  propeller  is  not  as  serious 
in  practice  as  it  is  in  theory. 

The  gyroscopic  action  of  the  single  propeller  is  more  dependent 
upon  the  factors  of  mass  and  speed.  With  heavy  propellers,  it  might 
undoubtedly  become  serious,  but  with  the  light  wood  propellers 


438 


AERIAL   PROPELLER  29 

so  generally  employed,  it  is  quite  as  negligible  a  quantity  as  the 
reaction  effect. 

Location  of  Propellers.  The  most  important  single  question  of 
design  still  unsettled  is  the  position  of  the  propeller.  There  is  a 
distinct  advantage  in  placing  the  propeller  at  the  rear  in  marine 
practice,  utilizing  a  pushing  or  propulsive  action,  on  account  of  the 
frictional  wake  created  behind  the  ship,  and  which  causes  the  water 
to  flow  after  the  vessel,  but  at  a  lesser  velocity.  In  placing  the  pro- 
peller behind,  it  is  put  in  such  a  position  as  to  act  upon  and  take 
advantage  of  this  phenomenon,  the  effect  of  the  propeller  being  to 
bring  this  wake  to  rest. 

Theoretically,  a  boat  can  be  propelled  with  less  power  than  is 
necessary  to  tow  it,  but  with  respect  to  aeroplanes,  apart  altogether 
from  the  difference  of  mediums,  there  is  at  present  a  very  consider- 
able difference  of  form,  an  aeroplane  bearing  but  little  resemblance 
to  the  hull  of  a  boat.  Undoubtedly  there  is  a  frictional  wake  in  the 
case  of  the  aeroplane,  perhaps  quite  as  much  as  in  the  case  of  a  boat, 
allowing  for  the  difference  in  medium.  Admitting  then  that  this  wake 
does  exist,  it  follows  that  a  propulsive  screw  is  better  than  a  tractor. 
In  a  matter  of  this  kind,  constructional  considerations,  as  well  as 
ease  of  launching  and  ability  to  land  without  damage,  must  be  given 
due  weight.  In  the  case  of  monoplanes,  constructional  details  have 
had  most  to  do  with  the  use  of  the  tractor  or  forward  position  of 
the  screw,  but  monoplanes  are  now  being  built  with  propulsive 
screws.  Good  results  have  been  obtained  in  a  small  flying  model 
equipped  with  two  screws,  placed  fore  and  aft  in  line  with  one  another, 
the  forward  screw  being  a  tractor  and  the  latter  a  propulsive  screw, 
but  so  far  as  the  writer  is  aware  this  arrangement  has  never  been 
tried  in  actual  practice. 

Experience  has  shown  that  no  improvement  whatever  is  obtained 
where  efficiency  is  concerned,  either  by  the  use  of  a  ring  connecting 
the  propeller  blade  tips,  or  by  the  employment  of  any  form  of  shroud- 
ing. It  has  frequently  been  considered  that  locating  the  propeller 
in  a  cylindrical  or  conical  chamber,  or  employing  some  form  of  guide 
through  which  the  air  is  led  to  the  propeller  is  necessary,  and  quite 
a  number  of  machines — few  of  which  have  ever  flown,  by  the  way 
—have  incorporated  this  feature.  That  nothing  of  this  kind  is  an 
improvement,  either  when  placed  before  or  behind  the  propeller, 


30  AERIAL  PROPELLER 

is  now  self-evident.  The  air  does  not  fly  oil'  from  the  tips  of  the 
blades  under  the  influence  of  centrifugal  force,  as  has  been  com- 
monly supposed,  but  is  powerfully  drawn  inward  in  a  well-designed 
propeller,  so  that  the  maximum  efficiency  is  obtained  by  allowing 
it  to  revolve  in  a  free  air  space. 

Propeller  Efficiency.  The  efficiency  of  a  propeller  depends 
upon  two  fundamental  laws — the  law  of  kinetic  energy  and  the  law 
of  momentum.  A  propeller  rotating  upon  a  standing  machine 
discharges  a  certain  number  of  pounds  of  air  backward  every  second. 
The  law  of  kinetic  energy  is  expressed  by  the  equation 

(it  K 

w=   pr 

where  K  is  the  number  of  foot  pounds  of  energy  which,  when  applied 
to  a  body,  or  volume  of  air,  of  IT  pounds  weight,  will  give  it  a  velocity 
of  !  feet  per  second. 

The  law  of  momentum  is  expressed  by  the  equation 

F-  "'  V 

\\1  T 

where  F  is  the  force  in  pounds,  which,  applied  to  a  body,  or  volume 
of  air,  of  II  pounds  weight  for  a  time  T  seconds,  gives  it  a  velocity 
of  I'  feet  per  second. 

But  there  are  two  meanings  of  the  term  "propeller  efficiency." 
One,  the  true  efficiency,  is  the  useful  work  of  the  propeller,  divided  by 
the  power  absorbed  by  it.  The  useful  work  is  the  speed  of  the  aero- 
plane, multiplied  by  the  thrust  of  the  propeller  while  driving  the 
machine  at  that  speed,  and,  of  course,  the  power  absorbed  is  the 
brake  horse-power  (in  foot  pounds)  of  the  engine  at  the  number  of 
revolutions  made  under  those  conditions,  less  the  power  lost  in 
transmission. 

The  other  meaning  of  propeller  efficiency  is  simply  the  thrust 
c.rcrtcd  by  the  propeller  when  revolving  at  a  fixed  point,  multiplied 
by  the  pitch  velocity,  and  divided  by  the  foot  pounds  delivered  to 
it  by  the  engine. 

The  pitch  velocity  is  the  pitch  times  the  number  of  revolutions 
per  minute. 

It  is  efficiency  in  the  latter  sense  that  is  considered  here,  and  a 


440 


AERIAL   PROPELLER  31 

comparison  of  two  propellers  of  different  diameters  will  show,  in  a 
striking  manner,  the  increase  in  efficiency  with  increase  in  diameter. 
Take,  for  example,  two  propellers  rotating  on  standing  machines 
using  the  same  horse-power,  but  of  different  diameters.  The  given 
horse-power  acting  on  the  smaller  amount  of  air  in  the  smaller  pro- 
peller gives  the  discharged  air  a  higher  velocity  than  with  the  larger 
propeller.  This  velocity  corresponds  somewhat  to  the  slip  in  a  pro- 
peller on  a  moving  machine  and  should  not  be  mistaken  for  the 
velocity  of  the  machine. 

Let  the  two  propellers  be  of  such  sizes  that,  for  one  horse-power 
applied  to  each,  the  velocity  given  to  the  discharged  air  by  the  small 
one  would  be  40  feet  per  second,  and  by  the  larger  one  20  feet  per 
second.  One  horse-power  is  equivalent  to  550  foot  pounds  of  energy 
expended  per  second.  Consider  the  law  of  kinetic  energy  as  applied 
to  the  volume  of  air  discharged  in  one  second  by  the  two  different 
propellers.  We  have  for  each  propeller,  7v  =  550  foot  pounds;  T= 
40  and  20  feet  per  second,  respectively.  Then  the  weight  W  of  air 
discharged  by  the  small  propeller  in  one  second  is 

04  K      04  X  550 
I  2  ~TvT      =  ~~  pounds  of  air 


Again,  for  the  larger  propeller 
04  X  550 


2()2 


=  cScS  pounds  of  air 


Now  that  we^have  the  values  of  II',  or  the  weights  of  the  air 
discharged  in  each  case,  we  can  apply  them  in  the  equation  of  momen- 
tum and  ascertain  the  force  applied  to  the  air,  or  the  thrust  of  the 
propellers. 

For  the  smaller  propeller  we  have 

W  V      22  X  40 

=  &>~T  =  IvxT  =  27'5  pounds  thrust 

Again,  for  the  larger  propeller 

88  X  20 
F  =  =  55  pounds  thrust 

6Z  A  1 


441 


32  AERIAL  PROPELLER 

Of  course,  in  these  calculations,  the  losses  due  to  skin  friction 
and  to  the  churning  of  the  air,  are  neglected,  but  the  figures  show  a 
striking  comparison  in  favor  of  the  larger  propeller,  both  in  having 
smaller  slip  and  in  giving  a  higher  thrust  than  the  smaller  one  for 
the  same  amount  of  energy  in  each  case  expended  in  producing  slip. 


442 


AERONAUTICAL  PRACTICE 

PART  I 


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STABILITY   OF   THE   AEROPLANE 

Variations  of  Center  of  Pressure.  When  an  aeroplane  of  any 
shape  is  placed  at  various  angles  in  a  current  of  air,  it  is  found  that 
the  point  at  which  thepressure  acts,  i.e.,  the  center  of  pressure, 
varies  with  every  inclination. 
This  variation  or  travel  of  the 
point  of  application  of  the  center 
of  pressure  differs  with  every  sec- 
tion and  plan  shape  of  aerocurve 
or  aeroplane.  With  certain  aero- 
curves  and  with  all  aeroplanes 
the  center  of  pressure  appears  to 
travel  continuously  toward  the 
front  edge  as  the  inclination  is 
continuously  decreased.  In  Fig.  1  is  shown  the  locus  of  the  center 
of  pressure  for  rectangles  having  an  aspect  ratio  of  three  to  one  in 
length  and  width  aspects.  In  both  cases  the  center  of  pressure 
continuously  advances  with  decrease  of  inclination. 

Fig.  2  shows  a  similar  locus  for  an  aerocurve  having  a  camber 
°f  iV  span,  and  an  aspect  ratio  of  3  to  2,  curve  2  representing  the 
hollow  upward  and  curve  1  the  x 

hollow  downward.  The  curve  2 
indicates  strong  stability,  and  the 
curve  1,  an  absence  of  stability. 
These  and  the  following  curves 


O         ./          ./?  3         .-f-          .5  6 

PftOPOKT/OM  OF  W/Om  fROM  FftOMT  ED6E 


Fig.  1.    Center  of  Pressure  Curves  for  Rec- 
tangular  Planes.    Aspect  Ratio  3  to  1 


of  the   center  of  pressure  were 

taken  /o  inch  above  the  highest 

point  in  the  plane,  the  greatest 

dimension  of  the  plane  being  9 

inches.     A.  P.  Thurston,  who  made  the  series  of  experiments  here 

recorded,  found   it   preferable   to   obtain   corresponding   curves   in 

Copyright,  1912,  by  American  School  of  Correspondence. 


FROM  FftO/YT  EDGE 

Fig.  2.     Locus  of  Center  of  Pressure  at 
Different  Inclinations 


443 


£)OOO/ 


2  AERONAUTICAL   PRACTICE 

addition  below  the  planes,  since  the  resultant  pressure  becomes  more 
inclined  to  the  normal  as  the  inclination  of  the  plane  is  decreased. 
Then,  by  the  combination  of  the  two  curves  so  obtained,  it  is  possible 
to  find  the  travel  of  the  center  of  pressure  for  any  other  parallel  line. 
The  stability  of  a  flying  machine  depends  upon  the  continuous  travel 
of  the  center  of  pressure  toward  the  front  edge  with  decrease  of 
inclination. 

Conditions  for  Stability.  The  center  of  gravity  and  the  center 
of  pressure  coincide  under  normal  conditions  when  a  flying  machine 
is  running  at  the  natural  angle  and  speed,  but  when  the  angle  is  too 
small,  the  center  of  pressure  approaches  the  front  edge  and  forms, 
with  the  weight,  a  couple  tending  to  restore  the  machine  to  its  nat- 
ural inclination.  Conversely,  if  the  inclination  be  too  great,  the 

center  of  pressure  travels  behind 
the  center  of  gravity  and  forms 
a  couple  tending  to  decrease  incli- 
nation. It  follows,  as  the  first 
necessary  condition  for  maximum 
stability,  that  the  travel  of  the 
center  of  pressure  to  either  side 
of  the  center  of  gravity  should  be 
a  maximum  for  a  minimum  alter- 
ation in  the  angle  of  inclination. 
As  the  second  condition,  it  follows  that  the  moment  of  inertia 
of  the  machine  about  a  lateral  axis  through  the  center  of  gravity 
should  be  a  minimum,  since  the  inertia  of  the  machine  resists  the 
action  of  the  restoring  couples.  The  restoring  couple  at  any  point 
is  the  product  of  the  lift  by  its  distance  from  the  vertical  through 
the  center  of  gravity.  Since  the  lift  is  a  function  in  the  equation 
of  stability,  it  follows,  as  the  third  condition  for  maximum  stability, 
that  the  decrease  of  lift  with  decrease  of  inclination  should  be  a 
minimum.  In  the  ideal  condition,  the  lift  should  increase  as  the 
inclination  is  decreased  from  the  natural  angle.  This  is,  of  course, 
impossible  in  practice.  If,  when  a  machine  has  received  a  small 
displacement  from  the  natural  angle,  a  perpendicular  through  the 
center  of  lift  is  drawn  to  cut  the  line  which  passes  through  the  center 
of  gravity  and  which  is  perpendicular  when  the  machine  is  at  the 
natural  inclination,  a  point  is  obtained  the  position  of  which  affects 


Fig.  3.     Stability  Curves  for  Rectangular 
Planes 


444 


AERONAUTICAL   PRACTICE 


the  stability  of  the  machine.  This  point,  which,  to  coin  an  expres- 
sion, might  be  called  the  "phugoid  center"  corresponds  to  the  meta- 
center  of  vessels,  and  its  height  above  the  center  of  gravity  gives  a 
measure  of  the  longitudinal  stability  of  a  flying  machine. 

In  Figs.  3  and  4  are  shown  the  stability  curves  of  rectangular 
planes  having  aspect  ratios  of  3  to  1  in  length  and  width  aspects, 
respectively.  Models  were  made  and  the  centers  of  gravity  care- 
fully adjusted  until  the  best  flights  were  obtained.  Good  flights 
were  obtained  with  center  of  gravity  located  0.28  of  the  width  from 
the  front  edge.  The  models  were  then  pivoted  about  these  points,  and 
the  vertical  torque  resisting  a  displacement  from  the  natural  inclina- 
tion was  measured;  this  is  plotted  in  Figs.  3  and  4.  Fig.  4  is  an  enlarge- 
ment of  a  portion  of  Fig.  3.  Curve  a  shows  the  plane  in  the  length 
aspect,  and  curve  b  in  width  aspect. 
The  rectangle  in  length  aspect 
clearly  has  a  much  greater  stability 
than  the  same  rectangle  in  width 
aspect.  The  restoring  torque  is 
(/>  W  A  V2  pound  feet,  <f>  being  the 
stability  coefficient  for  any  devia- 
tion from  the  natural  flying  angle 
and  read  from  the  diagrams,  Figs. 
3  and  4;  W  the  width  of  plane 

feet,  back  to  front,   taken   in   the  direction 


Fig. 


Stability  Curves.      Enlarged 
Detail  of  Fig.  3 


the 


in    leet,   bacK  to  iront,   taKen   in   me  direction   of  motion;  A 
area  in  square  feet,  and  V  the  velocity  in  miles  per  hour. 

Methods  of  Increasing  Stability.  The  stability  of  a  machine 
may  be  increased  by  placing  a  second  or  rider  plane  in  front  of  or 
behind  the  main  plane.  For  maximum  efficiency  in  flight,  the  main 
plane  should  have  the  shape  and  area  giving  the  maximum  lift  effi- 
ciency, i.e.,  it  should  be  approximately  a  rectangle  in  length  aspect. 
The  shape  of  the  main  plane  being  thus  fixed,  it  is  possible  to  vary 
the  shape  and  disposition  of  the  rider  plane  only  for  the  purpose  of 
increasing  the  stability.  Now  the  travel  of  the  center  of  pressure 
might  be  increased  if  it  were  possible  to  cause  the  pressure  on  a  front 
rider  plane  to  decrease  at  a  less  rate  than  the  pressure  on  the  main 
plane,  and,  conversely,  with  a  tail  rider  plane,  to  decrease  at  a  greater 
rate  than  that  on  the  main  plane.  This  result  may  be  obtained  by 
each  or  all  of  the  following  means: 


445 


4  AERONAUTICAL   PRACTICE 

Placing  a  front  rider  plane  at  a  positive  angle  with  the  main  plane, 
i.e.,  at  a  greater  angle  to  the  air  than  the  main  plane,  and  a  rear  rider 
at  a  negative  angle,  i.e.,  at  a  less  angle. 

By  utilizing  the  wake  of  the  front  plane  to  affect  the  back  plane. 

By  the  use  of  certain  shapes  and  aspects  of  planes  for  the  front 
and  rear  riders,  respectively. 

Front  and  Rear  Rider  Plane.  If  the  front  rider  is  at  a  positive 
angle,  then,  as  the  inclination  decreases,  it  is  obvious  that  the  pres- 
sure on  the  main  plane  will  decrease  at  a  greater  rate  than  that  on 
the  rider,  since  the  rider  will  still  be  lifting  when  an  angle  is  reached 
at  which  the  main  plane  ceases  to  lift.  Conversely,  if  the  rider  is 
set  at  a  negative  angle,  then,  as  the  inclination  of  the  machine  decreases 
the  front  plane  will  reach  an  angle  at  which  it  ceases  to  lift,  and  upon 
a  still  further  decrease  in  inclination  the  air  will  act  upon  the  top  of 
it  and  introduce  a  depressing  force.  This  force  will  oppose  the  couple 
introduced  by  the  travel  of  the  center  of  pressure.  Thus  it  follows 
that  the  front  rider  should  be  set  at  a  positive  angle  with  the  main 
plane.  From  a  similar  reasoning  it  follows  that  a  tail  rider  should 
be  set  at  a  negative  angle  with  the  main  plane.  It  will  be  evident  that 
the  original  arrangement  of  the  Wright  machine  with  the  front 
rider  at  a  negative  angle  tended  to  decrease  the  natural  stability  of 
the  biplane,  and  this  was  probably  one  of  the  causes  that  led  to  its 
abandonment. 

"Wake  Effects."  Too  little  attention  appears  to  have  been  paid 
to  the  utilization  of  the  wake  effects  for  increasing  the  stability.  The 
air  which  is  engaged  by  an  'aeroplane  is  deflected  downward.  This 
downward  deflection  is  not  confined  to  the  air  in  the  immediate  run 
of  the  aeroplane,  but  extends  to  a  considerable  distance  above  and 
below  the  plane,  particularly  above.  The  field  of  an  aeroplane  is 
therefore  greater  than  its  run. 

A  series  of  original  stream-like  photographs  taken  with  the 
aid  of  smoke  in  a  current  of  air  having  a  speed  of  1,800  feet  per  min- 
ute demonstrated  this  very  clearly.  The  stream  of  air  flowed  out 
of  a  small  nozzle  so  that  it  could  be  positively  directed  at  any  point 
desired,  the  surfaces  experimented  with  being  models  of  the  sin- 
gle and  double  surface  elevating  planes  such  as  are  employed  on  the 
majority  of  standard  type  monoplanes  and  biplanes.  With  the 
monoplane  elevator  set  at  a  sharp  positive  angle  and  the  current 


446 


AERONAUTICAL   PRACTICE  5 

directed  horizontally,  the  air  considerably  above  the  plane  was  notice- 
ably influenced,  while  when  directed  straight  at  the  edge  of  the  plane 
the  air  divided  in  front  of  it,  closely  hugging  the  under  side  and  form- 
ing a  "surface  of  discontinuity"  on  the  back.  Directing  it  at  the 
center  of  the  plane,  the  angle  of  incidence  being  the  same  in  every 
case,  clearly  showed  the  compression  under  the  plane  as  well  as  the 
upward  spring  of  the  current  at  the  rear  to  counteract  the  suction 
above;  and  directing  the  stream  below  the  plane  showed  the  gentle 
downward  deflection  imposed  on  the  air  below  the  rear  edge  of  the 
plane,  indicating  that  the  air  entirely  below  the  plane  is  affected 
quite  as  much  as  that  above  it.  From  these  experiments  it  will  be 
apparent  that  the  air  at  the  rear  of  an  aeroplane  is  in  a  considerable 
state  of  agitation  which  varies  from  point  to  point.  Now  the  lift- 
ing effect  of  this  air  in  the  wake  is  not  so  good  as  that  of  undisturbed 
air;  moreover,  since  this  air  has 
on  the  average  a  downward  de- 
flection, an  effect  is  obtained  on 
the  rear  plane  similar  to  that  ob- 
tained by  placing  it  at  a  negative 
angle  with  the  front  plane.  Thus 
the  stability  may  be  increased  by 
placing  the  rear  plane  in  the 
wake  of  the  first  plane;  but 
there  is  an  additional  effect  to  be 
obtained  by  utilizing  the  wake. 

The  purpose  is  to  arrange  it  so  that  the  lift  on  the  rear  plane 
shall  decrease  at  a  greater  rate  than  that  on  the  front  plane.  Since 
the  lifting  effect  of  the  wake  is  not  so  good  as  that  of  undisturbed 
air,  it  follows  that  this  object  may  be  attained  by  arranging  the  rear 
plane  to  enter  the  wake  when  the  inclination  is  decreased,  and  to 
come  out  of  it  into  the  free  air  when  the  inclination  is  increased. 
The  best  place  for  mounting  the  rear  plane  to  obtain  the  maximum 
effect  by  this  means  can  be  determined  only  by  experiment  and  by 
drawing  the  stability  curves,  as  in  Figs.  3  and  4,  and  the  curves  for 
the  travel  of  the  center  of  pressure,  as  in  Figs.  1  and  2. 

Rider  Planes  of  Certain  Shapes  and  Aspects.  The  third  method 
of  increasing  the  stability  is  by  the  use  of  rider  planes  having  cer- 
tain shapes  and  aspects;  for  instance,  these  shapes  may  take  a 


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90°    80°  70"   60°  50°  4O°  30°  30°  !O°    0 

INCLINA  TION  JN  DEOffEES. 

Fig.  5.      Lift  on  Planes  at  Various  Inclinations 

Planes  3X1  Inches,  Velocity  of  Air 
21  Feet  per  Second 

447 


6  AERONAUTICAL   PRACTICE 

square,  rectangular,  circular,  semicircular,  triangular,  or  other  plan 
form.  Of  these  a  rectangle  in  length  aspect  and  having  the  greatest 
aspect  ratio  has  a  greater  lift  per  unit  of  area  at  small  angles 
than  any  other  shape.  In  Fig.  5,  which  is  derived  from  Dr.  Stan- 
ton's  experiments  on  a  plane  having  an  aspect  ratio  of  3  to  1,  the 
lift  on  the  plane  in  length  aspect  at  angles  between  zero  and  20 
degrees  (see  curve  a)  is  much  greater  than  that  on  the  plane  in  width 
aspect  (curve  b) .  Moreover,  for  angles  above  20  degrees  the  pressure 
decreases  proportionately  (curve  a)  at  a  less  rate  than  in  the  case  of 
the  same  rectangle  in  width  aspec-t  (curve  b) .  Therefore,  a  rectangle 
in  length  aspect,  and  having  a  large  aspect  ratio,  is  the  best  shape 
for  a  front  rider.  The  shape  of  planes  having  the  greatest  propor- 
tional decrease  with  inclination  appears  to  be  either  a  triangle  with 

tA         its  apex  to  the  wind,  or  a  rectangle 
in  width  aspect.    The  superiority 
a    T  of  the   triangle   in  this   respect 

Fig.  6.     Main  and  Tail  Planes  -,  PHI  i 

has  not  been  fully  demonstrated 

by  experiment,  but  it  has  proven  unusually  successful  in  some  of 
the  French  monoplanes  such  as  the  Antoinette.  It  is  clear  that 
there  is  a  greater  proportional  decrease  with  inclination  for  planes 
having  a  smaller  width  aspect.  Therefore,  it  follows  that  the  tail 
planes  should  have  a  smaller  aspect  ratio  than  the  front  planes. 

The  center  of  area  of  a  triangle  with  its  apex  to  the  wind  would  be 
farther  from  the  center  of  gravity  of  the  machine  than  the  center  of 
area  of  a  rectangle  of  equal  area  in  width  aspect.  A  greater  restor- 
ing torque  would,  therefore,  be  obtained.  Moreover,  for  equal  areas 
of  tail  plane,  a  triangular  tail  would  have  double  the  span  of  a  rectan- 
gular plane,  and,  therefore,  take  approximately  double  the  advantage 
of  the  wake  effect.  It  would  thus  appear  from  these  considerations 
that  a  tail  rider  plane  should  preferably  be  triangular,  with  the  apex 
toward  the  wind.  Conditions  represented  by  curves  b  and  c  (see  Fig. 
11)  appear  to  require  aspect  ratios  of  opposite  values;  thus  it  follows 
that  the  relation  of  the  dimensions  should  be  fixed  by  experiment. 

Methods  of  Producing  Effective  Damping  Couple.  The  problem 
of  stability  is  not  completely  solved  by  the  provision  of  a  suitable 
restoring  couple.  It  is  necessary  to  provide,  in  addition,  an  efficient 
damping  couple  to  damp  out  any  oscillation  which  may  be  set  up. 
This  damping  couple  is  provided  by  the  resistance  offered  to  the 


448 


i^' 


AERONAUTICAL   PRACTICE  7 

planes  as  they  oscillate  in  the  air  above  the  center  of  gravity  of  the 
machine.  If,  in  Fig.  6,  A  equals  area  of  the  tail  plane,  B  equals 
the  area  of  the  main  plane  and  X  is  the  center  of  gravity  of 
the  system,  then  AXb  equals  BXa.  Therefore,  since  the  areas  of 
both  planes  A  and  B  are  constant,  the  distances  a  and  6  must  also 
be  constant.  For  a  given  angular  velocity  of  oscillation  about  the 
center  of  gravity  X,  the  velocity  v  of  the  plane  A  is  proportional  to 
the  distance  b;  and  furthermore  the  resistance  offered  by  the  air  to 
a  plane  is  proportional  to  the  square  of  the  velocity.  Therefore, 
the  damping  couple  introduced  by  the  rider  plane  A  equals  resist- 
ance X  b,  i.  e.,  y2  X  A  X  b.  But  it  has  already  been  sated  that  v  is 
proportional  to  b  and,  therefore,  the  damping  couple  is  proportional 
to  Ab*  or  to  Ab(b2) ;  i.e.,  the  damping  couple  provided  by  rider  planes 
having  equal  control  torque  increases  as  the  square  of  the  distance 
from  the  center  of  gravity.  The  distance  between  the  planes  should, 
therefore,  be  as  large  as  is  prac-  go1 
ticable,  which  doubtless  accounts  ^  ^, 
for  this  characteristic  of  the  most 
successful  French  monoplanes, 
such  ao  me  Bleriot,  in  which  the 
fuselage  or  tail  is  extremely  long. 
Also  it  follows  that  a  triangular  | 
tail  gives  a  more  powerful  damp- 
ing action  than  a  rectangular  Fig  7 
width  aspect  tail.  From  the  * 

previous  reasoning  it  would  appear  that  for  maximum  longitudinal 
stability,  i 

(1)  With  the  rider  plane  in  front,  the  rider  should  have  a  large 
aspect  ratio  in  length  aspect,  and  a  long  span  approximating  to  that 
of  the  rear  main  plane. 

(2)  With  the  rider  plane  behind,  the  rider  should  have  a  smaller 
aspect   ratio   than   the   front   main   plane,  and   should   preferably 
be  triangular  with  the  apex  toward  the  wind  and  placed  so  as  to 
take  advantage  of  the  wake  effects. 

(3)  In  both  cases  the  rider  plane  should  be  set  as  far  as  possible 
(within  limits)  from  the  main  plane,  the  planes  should  be  set  at  a 
positive  angle  with  each  other,  and  the  moment  of  inertia  of  the 
machine  should  be  a  minimum. 


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Center  of  Pressure  Curves  for  Plan 
Shapes  of  Figs.  8  and  10 


449 


8 


AERONAUTICAL   PRACTICE 


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Fig. 


Center  of  Pressure  Curves  for  Plan 
Shape  Inset 


plane  9Xi  inch  in  length  aspect. 


Study  of  "Center  of  Pressure"  Curves.  Center  of  pressure 
curves  for  flying  machines  of  various  plane  shapes  and  dispositions 
are  shown  in  Figs.  7,  8,  9,  10,  and  11.  In  all  these  cases  the  main 

plane  is  rectangular,  9  by  2 
inches,  the  aspect  ratio  is  thus  4| 
to  1.  This  rectangle  is  fixed  to 
one  end  of  a  rib  with  its  length 
at  right  angles.  The  rider  planes 
are  adapted  to  be  pivoted  at  the 
other  end  of  the  rib  7  inches 
from  the  outside  long  edge  of  the 
main  plane.  The  curve  a,  Fig.  7, 
is  obtained  with  a  front  rider 
Its  aspect  ratio  is  therefore  18 
to  1.  Curve  b  is  a  corresponding  curve  with  a  square  front  rider  of 
equal  area  to  the  last.  In  both  cases,  the  rider  and  main  planes  are 
parallel.  The  increased  stability  obtained  by  the  rectangular  rider 
is  apparent.  If  allowance  is  made  for  the  increased  longitudinal 
length  of  the  model  with  a  square  front  rider,  the  superiority  of  the 
rectangular  rider  is  still  more  marked.  Curve  a  between  the  points 
B  and  C  was  found  to  be  unstable,  it  being  found  impossible  to 
obtain  definite  points  of  balance. 

Fig.  8  shows  curves  a  and  b  obtained  with  the  first  model,  hav- 
ing the  rectangular  front  rider  at  a  positive  and  negative  angle  of 

5  degrees,  respectively.  Curve  a 
is  obtained  with  the  rider  at  plus 
5  degrees  with  the  main  plane. 
This  disposition  gives  a  strong 
stability.  In  curve  b,  with  the 
rider  set  at  a  negative  angle 
with  the  main  plane,  there  is  a 
lack  of  stability,  the  center  of 
pressure  traveling  toward  the 


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^ffOPO/fT/ON  OF  LENGTH  fftOM  THE 
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Fig.  9. 


Center  of  Pressure  Curves  for  Plan 
Shape  of  Fig.  8 


below  13   degrees.     The 


rear   for   all  decreases  of  angle 
curves  were   also   found   to   be   unstable 
between  the  points  A,  B,  and  A',  B'. 

Curves  a  and  b,  Fig.  9,  show  the  same  model  with  the  rectangu- 
lar front  rider  at  plus  10  degrees  and  minus  10  degrees,  respectively. 


450 


AERONAUTICAL   PRACTICE 


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Fig  10 


Center  of  Pressure  Curves  for 
Plan  Shape  Inset 


Curve  a,  with  the  rider  at  plus  10  degrees,  shows  a  stronger  sta- 
bility than  the  previous  curve  a  of  Fig.  8,  and  curve  6  shows  a  cor- 
respondingly greater  lack  of  stability.  Again  it  was  found  impos- 
sible to  obtain  definite  reading 
between  the  points  A  and  B,  but  ^ 
no  such  difficulty  was  found  with  ^ 
curve  6. 

Fig.  10  shows  curves  corre-  § 
spending  to  those  in  Fig.  9,  but  | 
with  a  square  front  rider  of  equal  | 
area.  The  planes  are  set  at  plus 
10  degrees  and  minus  10  degrees, 
respectively,  in  curves  a  and  6. 
These  curves  are  very  similar  in  characteristic  shape  to  those  of 
Fig.  9,  but  in  neither  case  is  the  stability  or  instability  so  strongly 
marked.  The  portions  of  the  curves  indicating  the  stability  lie 
between  3  and  15  degrees.  It  is  clear  that  the  travel  of  the  curves 
between  these  inclinations  is  smaller  in  Fig.  10  than  in  Fig.  9.  Curve 
a  is  discontinuous  between  the  points  A  and  B. 

Fig.  11  shows  the  center  of  pressure  curve  for  a  Bleriot  dispo- 
sition with  a  rectangular  main  plane  and  a  triangular  tail  rider. 
The  planes  are  in  all  cases  at  plus  10  degrees  to  each  other.  Curve 
a  shows  great  stability.  The 
center  of  pressure  travels  in 
front  of  the  front  edge  of  the 
main  plane.  The  equilateral 
triangular  plane  is  pivoted  at 
its  centroid  and  has  an  area 
equal  to  the  square  and  rec- 
tangular riders  previously 
used.  It  is  mounted  at  the 
rear  of  the  main  plane  with  its 
apex  to  the  wind.  In  curve 
a  the  triangular  plane  is  mounted  &  inch  below  the  main  plane  and 
in  curve  b  $  inch  above.  The  difference  in  the  curves  a  and  b  is 
therefore  to  be  attributed  solely  to  the  wake  effects.  Curve  a  gives 
a  superior  stability  to  curve  b.  Curve  c  is  obtained  with  the  model 
used  in  curve  a  with  the  same  angle,  the  current  being  reversed.  Thus 


PRECENTAGE  OF  LENGTH  FROM  THE  PJVOT 
PO/NT  TO  THE  REAR  EDGE.  CURVE  (c). 
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PROPORT/OM  OF  LENGTH  FffO/V  FffO/VT EDGE 
TO  THE  P/VOT  PO/HT.   CURVES  (a)  &(b).  -* 


Fig.  11. 


Center  of  Pressure  Curves  for  Bleriot 
Plan  Shape  Inset 


451 


10  AERONAUTICAL   PRACTICE 

the  main  plane  becomes  a  rear  plane,  and  the  triangular  tail  a  front 
elevator  with  its  base  to  the  wind.  The  line  X  Y  is  the  vertical  base 
line  for  this  curve,  and  corresponds  with  the  back  of  the  main  plane. 
Curve  c  has  been  superposed  on  curves  a  and  b  to  show  the  effect  of 
plane  shape  and  disposition  on  the  travel  of  the  center  of  pressure 
and  the  stability.  These  experiments  were  carried  out  in  the  aero- 
dynamical laboratory  of  the  University  of  London. 

It  will  be  apparent  that  the  problem  of  stability  resolves  itself 
into  keeping  the  center  of  pressure  and  the  center  of  gravity  in  the 
same  vertical  line  while  sailing  through  the  rolling  masses  of  air 
that  constitute  every  wind,  the  principle  being  exactly  the  same  as 
in  the  dirigible  although  in  the  latter  the  putting  it  into  prac- 
tice is  not  attended  by  as  many  complications.  The  first  investi- 
gators tried  to  do  this  in  their  gliding  experiments  by  shifting  their 
weight  while  gliding,  but  found  it  a  difficult  and,  at  times,  an  impos- 
sible task.  For  instance,  Lilienthal,  after  making  more  than  a 
thousand  successful  glides,  was  overturned  and  killed.  The  first 
successful  departure  from  this  crude  method  was  that  of  the  Wright 
Brothers  who  employed  a  horizontal  rudder  or  rider  some  distance 
in  front  of  the  main  plane,  by  which  the  machine  could  be  prevented 
from  overturning  frontward  or  backward.  This  principle — that 
of  operating  stabilizing  planes  to  overcome  or  to  counteract  every 
variation  of  the  position  of  the  center  of  pressure  due  to  changes  in 
the  velocity  and  direction  of  the  wind  as  originated  by  the  Wrights 
—was  what  made  flying  possible,  and  it  is  now  employed  on 
every  successful  aeroplane.  As  demonstrated  by  the  experiments 
just  recorded,  however,  it  was  found  that  the  front  rider  did  not 
take  advantage  of  the  wake  effects  and  was  not  as  efficient  a  pre- 
server of  stability  as  the  rudder  in  the  rear;  later  Wright  machines 
all  were  built  in  this  manner,  the  only  surfaces  forward  of  the  main 
planes  being  two  small,  fixed  fins  or  keels  to  give  greater  inherent 
lateral  stability.  In  all  monoplanes,  the  stabilizing  surfaces  are 
at  the  rear  and  some  distance  behind  the  main  plane,  it  being  possi- 
ble to  reduce  the  area  of  these  surfaces  in  proportion  to  the  increased 
leverage  afforded  by  their  greater  distance  from  the  main  plane. 

With  the  elevators  and  stabilizing  planes  of  moderate  size 
and  placed  at  moderate  distances  from  the  center  of  gravity,  the 
balance  of  the  aeroplane  may  be  kept  under  control  in  the  most 


452 


AERONAUTICAL   PRACTICE  11 

irregular  winds,  provided  these  auxiliary  surfaces  are  always  set  at 
the  proper  angle  to  give  the  desired  restoring  effect  as  determined 
by  the  rapidly  shifting  conditions.  But  when  it  is  recalled  that, 
at  times,  even  the  birds  are  upset  by  gusts  of  wind,  and  sometimes 
fall  to  the  ground  before  they  can  recover  their  equilibrium,  it  is  not 
surprising  that  occasions  should  be  encountered  in  which  the  most 
experienced  aviator  is  not  quick  enough  to  set  the  rudders  to  meet 
every  gust.  It  is,  therefore,  essential  that  the  aeroplane  should  be 
possessed  of  sufficient  inherent  stability  to  supplement  the  aviator's 
efforts  in  times  of  emergency,  or  that  it  be  equipped  with  a  controller 
which  will  automatically  adjust  the  balancing  surfaces  independently 
of  the  aviator.  The  latter  is  a  subject  that  is  at  present  engrossing 
the  attention  of  many  of  the  foremost  investigators  in  this  field  and 
it  is  treated  of  in  detail  under  the  head  of  Automatic  Stability. 

Longitudinal  and  Lateral  Stability.  The  principle  on  which  the 
inherent  fore-and-aft,  or  longitudinal  stability  of  an  aeroplane 
depends  is  comparatively  simple.  The  center  of  gravity  of  the 
machine  is  placed  in  front  of  the  normal  center  of  air  pressure,  and 
the  forward  planes  are  inclined  at  a  greater  positive  angle  to  the 
line  of  flight  than  the  following  planes.  If  an  aeroplane  so  adjusted 
be  allowed  to  fall  from  a  great  height,  since  the  center  of  gravity  is 
forward  of  the  normal  center  of  pressure,  the  front  will  turn  down 
and  the  machine  will  dive  toward  the  ground.  Then,  when  it  has 
gained  sufficient  speed  from  gravity,  since  the  forward  rider  has  a 
greater  angle  of  incidence  than  the  main  planes,  the  front  receives 
a  proportionately  (^greater  air  pressure  and  the  machine  rights  itself. 
This  is  strikingly  illustrated  by  the  foolhardy  performance  vari- 
ously termed  the  "high  dive"  and  the  "dip  of  death,"  practiced  by 
professional  aviators  at  public  meets,  in  which  the  machine  is  allowed 
to  descend  from  a  height  of  1,500  to  2,000  feet  at  an  angle  of  45  to 
60  degrees  until  it  has  attained  a  terrific  speed,  and  then  suddenly 
tilting  the  elevating  planes  when  within  a  few  hundred  feet  of  the 
ground,  thus  bringing  the  machine  up  sharply  on  an  even  keel,  and 
incidentally  putting  a  frightful  strain  on  every  part  of  the  aeroplane. 
As  soon  as  the  front  of  the  aeroplane  turns  up  again,  its  speed  dimin- 
ishes until  the  front  again  drops,  and  in  this  manner  its  flight  through 
the  air  may  be  kept  constant  when  driven  by  the  motor.  What  is 
commonly  known  as  "volplaning" — descending  from  a  height  without 


453 


12  AERONAUTICAL   PRACTICE 

the  motor,  is  simply  a  succession  of  these  dives,  followed  by  alternate 
periods  of  sailing  on  an  even  keel  or  at  a  slight  upward  angle. 

There  are  two  different  principles  by  which  inherent  lateral 
stability  is  secured.  The  first  of  these  is  simply  to  arrange  the  main 
supporting  surfaces  at  a  dihedral  angle,  or  to  use  vertical  surfaces, 
i.e.,  fins  or  keels,  with  a  low  center  of  gravity.  Both  of  these  con- 
structions give  the  same  result,  viz,  the  air  pressure  on  the  lower  side 
is  increased,  thus  causing  it  to  rise.  The  other  method  is  somewhat 
more  complicated  for,  in  this  case,  there  must  be  a  vertical  plane  at 
some  distance  behind  the  center  of  gravity.  If,  with  this  arrange- 
ment, the  aeroplane  tilts  to  one  side,  it  will  slide  sideways  until  the 
air  catches  the  vertical  plane  in  the  rear  and  turns  it  head  into  the 
wind.  The  result  is  that  instead  of  upsetting,  the  aeroplane  simply 
wings  around.  If  there  be  a  constant  upsetting  force,  however, 
the  radius  of  the  circle  becomes  smaller  and  smaller  and,  unless 
corrected  by  the  controlling  planes,  the  machine  strikes  the  ground 
banked  at  a  steep  angle.  But  this  principle  works  fairly  well  even 
"in  high  winds  and  is  employed  on  the  majority  of  successful  aero- 
planes. A  typical  instance  of  its  use  is  found  in  the  Antoinette  mono- 
plane in  which  a  large  vertical  surface  is  combined  with  a  triangular 
elevator  at  the  extreme  end  of  a  long  tail  frame  or  fuselage. 

However,  though  an  aeroplane  may  maintain  its  balance  in  still 
air  in  this  manner,  when  winds  arise  troubles  arise  with  them  and 
for  that  reason  the  beginner  is  always  cautioned  never  to  attempt 
a  flight  in  a  power-driven  machine  except  when  there  is  an  absolute 
calm.  Since  the  stability  of  the  machine  depends  upon  the  reaction 
of  the  air  upon  it  when  gravity  pulls  it  one  way  or  the  other,  the 
balance  is  disturbed  whenever  it  is  struck  by  wind  gusts.  For  instance, 
just  as  when  the  aeroplane  flies  too  rapidly  through  the  air  it  turns 
upward  until  its  velocity  decreases,  so  if  a  wind  strikes  it  in  front 
its  speed  through  the  air  is  increased  and  the  front  turns  up  and 
if  the  wind  comes  from  behind  its  speed  is  decreased  and  it  turns 
toward  the  ground.  If  the  wind  gust  is  sharp  and  the  aviator  is 
flying  low,  he  may  strike  the  ground  before  equilibrium  can  be  recov- 
ered, and  not  a  few  aviators  have  either  been  seriously  injured  or 
killed  in  this  manner,  it  being  thought  that  a  condition  of  this  nature 
was  responsible  for  the  death  of  Moisant  whose  machine  suddenly 
plunged  to  the  earth  from  a  height  of  only  one  hundred  feet. 


454 


AERONAUTICAL   PRACTICE  13 

It  has  been  determined  by  innumerable  experiments  with  every 
type  of  model,  that,  in  general,  the  closer  the  centers  of  gravity 
and  pressure  coincide,  the  less  the  longitudinal  stability  is  influ- 
enced by  variable  air  currents.  It  is  almost  impossible  for  a  well- 
balanced  aeroplane  to  be  completely  overturned  while  in  the  air,  but 
it  may  easily  be  tipped  to  an  angle  which  is  very  dangerous,  espe- 
cially when  close  to  the  ground.  This  method  of  obtaining  stability 
is  the  only  one  in  common  use  up  to  the  present,  but  it  has  been 
noted  that  while  it  works  very  well  in  calm  air,  it  may  become  a 
source  of  danger  rather  than  of  safety  when  used  in  gusty  winds. 
If  every  time  the  aviator  comes  within  one  hundred  feet  or  less 
of  the  earth  he  is  in  danger  of  being  dashed  precipitately  to  the 
ground,  the  aeroplane  can  scarcely  be  considered  a  practical  or 
safe  machine.  As  has  already  been  noted,  the  designers  of  successful 
machines  have  provided  ample  area  in  the  stabilizing  surfaces 
to  counteract  extremes  of  movement  of  the  center  of  pressure 
caused  by  variations  of  wind  velocity  and  direction,  so  that  if  it  be 
possible  in  any  manner  to  cause  these  balancing  planes  to  act  of 
their  own  accord  to  counteract  changing  conditions  as  rapidly  as 
they  arise,  perfect  equilibrium  in  the  most  sharply  varying  winds  will 
be  attained.  This  in  brief  is  the  problem  of  automatic  stability. 

AUTOMATIC   STABILITY 

As  at  present  constituted  the  lateral  stability  of  an  aeroplane 
is  largely  dependent  upon  the  aviator  himself.  That  it  is  precarious 
at  best  is  amply  evidenced  by  the  numerous  fatalities  among  skilled 
aviators,  many  of  which  have  undoubtedly  resulted  from  inability 
to  think  quickly  enough — to  always  do  the  right  thing  at  the  right 
moment.  Control  once  lost  is  apparently  lost  for  good,  if  the 
numerous  disastrous  plunges  to  the  ground  from  varying  heights 
that  have  followed  loss  of  control,  may  be  regarded  as  a  criterion. 
To  obtain  this  control  by  mechanical  means,  independent  of  the 
skill  and  dexterity  of  the  aviator,  is  accordingly  one  of  the  most 
generally  sought  improvements  in  the  aeroplane  today. 

Before  describing  some  of  the  more  important  devices  put  for- 
ward to  attain  this  end,  it  is  essential  that  a  clear  understanding  of 
what  is  meant  by  the  term  *  'automatic  stability"  be  had,  as  it  is 
very  generally  confused  with  ''inherent  stability."  Any  stabilizing 


455 


14  AERONAUTICAL   PRACTICE 

effect  brought  about  by  the  shape  of  the  planes  or  the  addition  of 
keels,  as  represented  by  the  numerous  vertical  partitions  between  the 
main  planes  of  the  first  Voisin  types,  is  merely  inherent  stability. 
This  is  due  to  the  form  of  the  machine  itself,  i.  e.  to  the  employment 
of  extra  surfaces  in  a  certain  way,  so  that  the  machine  has  a  natural 
tendency  to  right  itself  and  maintain  an  even  keel  in  flight.  This  is 
often  erroneously  referred  to  as  automatic  stability,  whereas  the 
latter,  in  the  real  sense  of  the  term,  can  be  accomplished  only  by 
some  extraneous  device  designed  mechanically  to  counteract  the 
adverse  effects  of  the  wind. 

PRINCIPLES  OF  CONTROL 

Balancing  is,  of  course,  automatic  in  the  case  of  a  bird  and  the 
method  employed  by  the  bird  may  possibly  be  imitated.  The  organs 
by  which  equilibrium  is  maintained  are  known  as  the  semicircular 
canals.  They  are  small,  hair-like  tubes  filled  with  fluid  lying  in 
three  planes  at  right  angles  to  one  another  in  the  bone  of  the  skull, 
each  tube  controlling  through  delicate  nerve-ends  the  movements 
of  the  bird  in  its  respective  plane.  Although  it  is  not  possible  to 
reproduce  artificially  such  a  complex  and  delicate  structure,  devices 
designed  to  act  in  much  the  same  manner  may  be  employed. 

Controllers  employed  to  regulate  the  supplementary  surfaces 
in  this  manner  may  be  divided  into  three  general  classes:  (1)  Those 
which  depend  for  their  balancing  properties  upon  the  action  of  the 
air  itself  when  the  position  of  the  aeroplane  is  altered;  (2)  those 
depending  upon  the  action  of  gravity,  such  as  pendulums;  and  (3) 
those  depending  upon  some  other  force  than  gravity  or  the  reaction 
of  the  air  to  control  the  balancing  planes. 

Air  Reaction  Principle.  The  most  simple  form  of  controller 
depending  upon  the  reaction  of  the  air  is  that  in  which  longitudinal 
stability  is  regulated  by  an  auxiliary  vertical  plane  struck  by  the 
wind  in  front,  and  lateral  stability  is  regulated  by  a  plane  acted 
upon  by  air  currents  from  either  side,  as  shown  in  Fig.  12.  In  this 
case,  when  the  aeroplane  turns  down,  the  increased  speed  increases 
the  pressure  on  the  wind  plane  A  and,  forcing  it  back,  elevates  the 
horizontal  rudder,  or  elevating  plane.  If  it  turn  up,  the  pressure 
diminishes  and  the  spring  B  brings  the  plane  forward  and  depresses 
the  rudder.  If  the  aeroplane  tilt  to  one  side,  it  slides  down  edge- 


456 


AERONAUTICAL  PRACTICE 


15 


wise  until  sufficient  pressure  results  on  the  surface  C  to  cause  the 
latter  to  adjust  the  ailerons  or  warping  edges  of  the  wings  to  coun- 
teract this  effect.  The  faults  of  this  type  of  automatic  control  are 
obvious.  Since  the  action  of  the  balancing  planes  depends  entirely 


Fig.  12.     Stability  Control  by  Auxiliary  Planes 

T 

upon  the  wind  striking  the  controlling  surfaces,  the  result  of  sud- 
den gusts  is  to  greatly  disturb  the  stability  of  the  machine.  In  fact, 
it  is  made  much  more  sensitive  to  suddenly  changing  conditions  than 
the  machine  which  secures  stable  equilibrium  by  means  of  fixed  sup- 
plementary surfaces  as  already  described. 

Longitudinal  Stability  Control.  To  eliminate  this  trouble  with 
wind  gusts,  the  Wright  Brothers  invented  an  automatic  controller 
of  longitudinal  stability  designed  to  maintain  the  aeroplane  flying  at 
a  definite  angle  of  incidence  instead  of  at  a  constant  velocity  through 
the  air.  The  principle  of  this  automatic  control  is  shown  in  Fig.  13, 
with,  however,  the  omission  of  compressed-air  connections  to  set  the 
horizontal  rudder  according  to  the  position  of  the  controller.  The 
regulating  plane  Al  is  placed  parallel  to  the  plane  of  flight,  and  is 


Fig.  13.      Diagram  of  Wright  Automatic  Stabilizer  without  Compressed-Air  Connections 


connected  by  levers  and  rods  with  the  elevator  L.  Whenever  the 
aeroplane  turns  up,  the  wind  strikes  the  under  side  of  A  l  moving  it 
to  A  2  and  depressing  the  rudder,  T>r  vice  versa.  It  will  be  apparent 
that  this  device  is  likewise  influenced  by  wind  gusts  but  not  so 


457 


16  AERONAUTICAL   PRACTICE 

strongly  as  the  type  just  mentioned  previously,  though  when  flying 
close  to  the  ground  it  would  probably  be  as  dangerous  as  the  usual 
manual  control,  should  the  machine  be  suddenly  struck  from  behind 
by  a  strong  gust  of  wind.  It  has  been  employed  in  experimental 
flights  but  the  Wrights  state  that  they  can  not  trust  it  as  fully  as 
they  can  their  own  skill  in  maintaining  the  equilibrium  of  the 
machine  in  gusty  winds. 

Wright  Brothers'  Patent.  The  Wright  Brothers  were  awarded 
a  patent  in  England,  in  ,1909,  on  this  device  (No.  2913-1909).  It 
is  described  as  follows: 

Using  compressed  air  or  other  fluid  pressure  as  power,  the  action  of  the 
contrivance  is  controlled  in  one  case  by  a  pivoted  vane  acting  under  the  influ- 
ence of  the  wind;  in  the  other  case  by  a  pendulum.  In  both  cases  the  con- 
troller is  merely  used  to  operate  a  three-way  valve,  its  influence  upon  the  manip- 
ulation of  the  steering  gear  or  front  control  (old  AVright  machine),  as  the  case 
may  be,  taking  place  through  the  agency  of  a  relay  which  the  opening  of  the 
valve  brings  into  action. 

This  relay  mechanism  consists  of  a  compressed-air  engine  which  is  linked 
up  to  the  steering  gear  or  front  control,  as  the  case  may  be,  by  means  of  a  con- 
necting rod.  The  engine  itself  is  operated  by  compressed  air  from  a  reservoir, 
which  would  presumably  be  maintained  or  kept  charged  by  a  pump  attached 
to  the  aeroplane  motor.  Regarding  the  compressed-air  system  as  the  principle, 
the  patent  covers  two  separate  and  distinct  applications  to  the  same  flyer. 
One  of  these  systems  is  exclusively  devoted  to  the  control  of  the  elevator,  i.  e., 
the  front  horizontal  control.  The  other  is  likewise  reserved  solely  for  the 
manipulation  of  the  vertical  rudder  and  the  warping  of  the  main  planes.  Each 
of  these  systems  has  its  own  reservoir,  or  compressed-air  tank,  engine,  and 
controller,  the  latter  apparatus  being,  as  already  mentioned,  a  pivoted  vane 
in  the  case  of  the  elevating  gear,  and  a  pendulum  in  the  other  instance. 

The  apparatus  consists  of  a  pulley  normally  under  the  control  of  the  avia- 
tor through  the  agency  of  a  lever,  but  embodies  such  features  in  its  construc- 
tion as  enable  it  to  be  coupled  up  to  the  connecting  rod  of  the  engine  which  is 
operated  from  the  tank  of  compressed  air.  There  are  two  connections  from 
this  tank  to  the  cylinder  of  the  engine,  the  one  to  the  lower  part  of  the  cylinder 
being  permanent,  while  that  to  the  upper  first  leads  to  the  three-way  valve 
designed  to  be  operated  by  the  automatic  movements  of  a  horizontal  vane,  or 
aeroplane,  mounted  on  an  arrangement  of  beams  forming  a  parallel  motion 
mechanism.  The  frame  upon  which  these  beams  are  pivoted  hangs  from 
brackets  mounted  on  an  adjacent  part  of  the  main  struts  of  the  flyer,  and  one  of 
its  members  is  prolonged  downward  to  form  a  handle  within  reach  of  the  aviator. 

The  advantage  of  this  arrangement  is  that  the  pilot  himself  may  reset 
the  course,  or,  as  it  may  be  better  described,  "the  neutral  line  of  flight;"  i.  e.,  if, 
after  having  flown  along  a  horizontal  course,  it  is  desired  to  ascend,  the  auto- 
matic mechanism  may  still  be  retained  in  action  to  guard  the  machine  against 
variations  from  its  ascending  path  by  merely  resetting  the  position  of  the  frame. 
Since  the  three-way  valve  is  mounted  upon  the  frame  and  because  the  beams 


458 


AERONAUTICAL   PRACTICE  17 

are  independently  in  equilibrium  as  a  whole  by  reason  of  the  balance  weight,  it 
will  be  evident  that  any  alteration  in  the  position  of  the  frame  will  at  once  affect 
the  state  of  the  valve;  i.e.,  if  open,  it  may  tend  to  close  it,  or  vice  versa.  Assume 
it  to  be  open  and  the  elevator  set  for  ascent,  then  should  the  pilot  wish  to  ascend 
permanently,  he  will  move  the  handle  so  as  to  open  the  valve  a  little  way.  This 
will  have  no  effect  directly  upon  the  position  of  the  controlling  vane  because 
the  balance  weight  serves  to  keep  it  horizontal  irrespective  of  the  position 
of  the  frame.  The  change  from  a  horizontal  to  an  ascending  flight  path, 
however,  will  automatically  result  in  a  change  of  the  real  altitude  of  the  vane 
to  the  relative  wind,  which  will  now  bear  upon  it  partly  from  above,  and  will 
thus  cause  it,  when  the  wind  is  strong  enough,  to  fall  a  little  and  close  the  valve. 
This  action  will  bring  the  relay  mechanism  into  action  and  will  alter  the  angle 
of  the  elevator  until  the  conditions  are  restored,  which  will  cause  the  control- 
ling vane  to  return  to  its  normal  position.  Naturally,  these  appliances  are  not 
dead  beat  and,  consequently,  oscillations  are  set  up  which  require  time  to  die 
out  and  it  is  more  than  likely  that  the  normal  state  of  affairs  would  be  one  in 
which  the  vane  is  constantly  moving  up  and  down. 

For  regulating  the  lateral  stability,  a  pendulum  is  employed  instead  of 
a  vane,  the  pendulum  being  suitably  coupled  to  the  valve  so  that  any  cant- 
ing of  the  flyer  from  its  normal  level  causes  the  valve  to  open  or  shut  accord- 
ing to  the  requirements.  The  pendulum  hangs  straight  down  like  a  plumb 
bob  under  the  influence  of  gravity  and  it  is  thus  really  the  movements  of  the 
machine  as  a  whole  about  the  pendulum  as  a  fixed  point  which  form  the  con- 
trol. In  practice,  the  normal  state  of  the  pendulum  control  would  presumably 
be  one  of  more  or  less  continuous,  though  possibly  slight,  oscillations.  In  the 
same  way  that  it  is  possible  for  the  vane  to  alter  the  neutral  line,  so  can  the  same 
variation  be  accomplished  with  the  pendulum,  and,  if  necessary,  the  flyer  be 
made  to  travel  in  a  circular  path  indefinitely. 

Regarding  this  patent,  Orville  Wright  stated  in  an  interview 
at  the  time  of  its  granting: 

The  device  which  the  English  are  making  such  a  fuss  about  is  an  old  con- 
trivance with  which  we  planned  to  get  automatic  stability  as  long  as  five  or 
six  years  ago.  That  WE(S  before  anybody  believed  that  flying  as  we  know  it 
today  was  possible.  Since  then  we  have  progressed  beyond  this  device  and 
have  others  which  may  be  great  improvements.  The  vane  and  pendulum 
device  is  a  very  simple  one.  It  can  be  adjusted  to  any  machine  in  a  few  min- 
utes and,  theoretically,  it  works  very  well.  We  have  used  it  often  but  I  do 
not  think  it  was  used  in  connection  with  any  big  flights.  Since  first  bringing 
it  out,  we  have  been  working  upon  several  devices  to  obtain  automatic  sta- 
bility. We  realize  that  if  we  can  make  an  aeroplane  balance  automatically  in 
the  air  while  in  flight,  it  will  be  a  very  important  step  forward. 

It  is  accordingly  apparent  that  a  wind  plane  is  not  an  entirely 
practical  device  to  employ  as  a  controller  either  in  a  horizontal  or  a 
vertical  position  when  used  in  either  of  the  ways  just  outlined,  or  in 
any  manner  partaking  of  the  characteristics  of  these  methods.  Con- 
sequently, this  eliminates  all  devices  in  that  class  for  the  time  being, 


459 


18 


AERONAUTICAL   PRACTICE 


and  the  value  of  the  pendulum,  as  being  the  chief  representative  of 
the  class  depending  upon  gravity  for  its  action,  may  be  considered. 


Fig.  14.     Diagram  Illustrating  the  Fault  of  Pendulum  Control 

Gravity  Principle.  The  effect  to  be  gained  by  the  use  of  this, 
as  illustrated  in  Fig.  14,  is  that,  when  the  aeroplane  changes  its  posi- 
tion with  respect  to  the  direction  of  the  force  of  gravity,  the  pendu- 
lum will  remain  vertical,  and  either  by  direct  connections  or  by 
operating  valves  for  compressed  air  or  by  making  contacts  which 
will  set  electrical  devices  in  action,  it  will  reset  the  balancing  planes 
so  as  to  re-establish  the  equilibrium  of  the  machine.  This  is  excel- 
lent in  theory  and  many  have  accepted  the  latter  blindly,  but  one 
great  difficulty  is  that  under  the  influence  of  sudden  gusts  the  pen- 
dulum is  likely  to  oscillate  so  violently  as  to  destroy  all  stability. 
This  is  not  insurmountable,  however,  as  these  oscillations  can  be 
damped  by  friction  or  a  water  bath  or  a  mercury  level,  as  shown  in 
Fig.  15.  But  even  if  these  oscillations  be  reduced  to  a  negligible 
point,  the  pendulum  when  used  as  a  controller  does  not  preserve  a 

vertical  position  except  by 
the  reaction  of  the  air  upon 
the  aeroplane,  and,  therefore, 
can  not  be  successfully  used. 
This  is  illustrated  by  Fig.  16. 
_i —  rr^=*L  If  the  aeroplane  be  tipped  at 

Fig.  15.     Mercury  Level  to  Dampen  Oscillations        &n  angje  ^  there  jg  aR  accej_ 

eration  due  to  gravity  tending  to  bring  the  pendulum  back  to  a  ver- 
tical position,  which  is  evidently  equal  to  g  sinN.     But  supposing 


460 


AERONAUTICAL   PRACTICE 


19 


the  resistance  of  the  aeroplane  to  motion  in  a  horizontal  plane  to  be 
zero,  when  tipped  at  an  angle  of  N  degrees  its  acceleration  is  also 
g  sin  N,  the  same  as  that  of  the  pendulum.  This  being  the  case, 
there  is  no  force  to  change  the  latter's  position  with  reference  to  the 
former.  If,  however,  as  is  always  the  case,  the  aeroplane  offers 
some  resistance  to  motion  in  a  horizontal  direction,  as  its  speed 
through  the  air  under  the  influence  of  gravity  is  increased,  the  resist- 
ance will  increase  and  its  acceleration  will  correspondingly  dimin- 
ish. The  controller  will  then  resume  its  perpendicular  position 
and  by  means  of  its  connections  adjust  the  balance  of  the  machine. 
But  here  the  former  difficulty  again  enters.  If  it  is  only  because  of 


Fig.  16.      Theoretical  Diagram  of  Action  of  Pendulum  Control 

the  air  resistance  that  the  air  controller  works,  it  will  be  affected  by 
wind  currents.  For  instance,  if  a  sharp  gust  of  wind  should  strike 
the  machine  from  one  side,  it  would  blow  the  wings  over,  while  the 
pendulum,  owing  to  its  inertia,  would  tend  to  remain  in  its  original 
position,  and  would  therefore  swing  toward  the  wind,  raising  the 
aeroplane  on  that  side.  In  fact,  so  many  have  pinned  their  faith  to 
the  pendulum,  and  still  do — purely  on  theoretical  grounds — that  a 
resume  of  the  manner  in  which  it  acts  under  all  conditions  will  be 
of  value  in  demonstrating  the  futility  of  further  attempts  along  this 
line.  This,  of  course,  refers  to  the  use  of  a  pendulum  as  a  direct 
agency  in  operating  the  controls  to  give  automatic  stability,  and  not 
to  a  small  pendulum  employed  as  a  relay  to  set  a  motor  in  operation, 
as  in  the  Wright  device.  However,  the  same  objections  would  be 
present  in  the  latter  device,  though  on  a  greatly  reduced  scale. 


461 


20 


AERONAUTICAL   PRACTICE 


The  manner  in  which  a  pendulum  device  is  relied  upon  to  give 
automatic  control  is  best  shown  by  reference  to  Figs.  17,  18,  and  19. 
Fig.  17  represents  a  longitudinal  section  of  a  pendulum  control  P 
for  fore-and-aft  balance,  and  an  elevator  rudder  E.  The  direction 
of  flight  is  indicated  by  the  arrow  and  in  this  same  diagram  the 
aeroplane  is  assumed  to  be  in  normal,  horizontal  flight.  Fig.  18 


Fig.  17.     Pendulum  Control.     Machine  Going  Steadily 


Fig.  18.     Pendulum  Control.     Restoring  Action  when 
Machine  Rears 


Fig.  19.      Pendulum  Control.      Restoring  Action  when 
Machine  Dips 


shows  the  same  apparatus  immediately  after  a  sudden  gust  has 
tilted  the  front  of  the  machine  up.  The  pendulum  P,  due  to  its 
inertia,  has  retained  its  vertical  position  P',  but  in  doing  so  has 
pulled  on  the  rod  ab,  causing  the  front  elevator  to  assume  the  posi- 
tion E'  and  to  receive  the  pressure  of  the  wind  on  its  upper  face. 
This  causes  a  downward  force  on  the  rudder  surface  which  brings 


4*52 


AERONAUTICAL   PRACTICE  21 

the  machine  back  to  the  horizontal.  Fig.  19  represents  the  effect  of 
a  sudden  downward  plunge  of  the  machine. 

In  the  same  manner,  the  inertia  of  the  pendulum  is  used  to 
move  side  controls  when  a  sudden  transverse  tilt  occurs.  Of  course, 
the  nature  of  the  pendulum  and  the  manner  in  which  it  controls  the 
equilibrium  is  vastly  different  in  many  of  the  suggested  methods, 
but  the  fundamental  principle  is  always  the  same,  the  pendulum 
itself  consisting  variously  of  an  extra  weight,  the  weight  of  the  car, 
the  weight  of  the  aviator  swinging  on  a  movable  seat,  or  the  move- 
ment of  a  mercury  bath. 

Objections  to  Pendulum  Devices.  There  are  four  distinct  objec- 
tions to  employing  any  kind  of  a  pendulum  device  for  automatic 
stability : 

(1)  The    most   important   objection  is  that,  if  the  pendulum 
is  at  all  heavy,  it  will  tend  when  the  machine  is  tilted  to  accen- 
tuate greatly  the  tipping.    Thus,  in  Fig.  18,  due  to  the  fact  that  the 
weight  Pf  has  traveled  through  an  angle  0,  with  respect  to  the  frame, 
there  will  be  a  strong  downward  pull  in  the  direction  BA.    This  will 
certainly  accentuate  the  downward  force  at  the  rear,  due  to  the 
vertically  downward  component  EC.    If  the  weight  is  heavy  enough, 
and  the  inclination  great  enough,  this  is  likely  to  completely  unbal- 
ance the  machine. 

(2)  Another  effect  upon  a  pendulum  mechanism  that  makes 
it  distinctly  undesirable  is  that  if  there  is  a  sudden  lurch  of  the  entire 
machine,  either  forward  or  backward  or  to  either  side,  unaccom- 
panied by  any  tilting,  then  the  inertia  of  the  pendulum  will  cause  it 
to  swing  away  from  the  side  to  which  the  machine  lurches,  thus  mov- 
ing the  rudder  and  actually  disturbing  the  equilibrium  of  the  machine, 
by  either  making  it  rise,  plunge,  or  tilt  over  to  one  side.     Due  to 
"holes  in  the  air,"  sudden  side  gusts,  and  even  variable  propeller 
thrusts,  such  sudden  lurches  are  of  more  or  less  frequent  occur- 
rence and  unless  some  means  of  deadening  the  pendulum  is  provided 
the  equilibrium  will  be  very  unstable. 

(3)  The  action  of  centrifugal  force  in  making  a  turn  will  cause 
the  pendulum  to  assume  a  position  parallel  to  the  struts  of  the 
machine,  or  of  any  other  normally  vertical  parts,  and  it  will  not  fly 
to  the  outside  as  is  commonly  supposed.    Its  action  in  turning,  there- 
fore, is  nil,  and  to  make  the  turn  positive  it  would  be  necessary  to 


463 


22  AERONAUTICAL  PRACTICE 

*  .»• 

install   a  separate   control.     This  arrangement  assumes   a  proper 
"banking"  of  the  machine. 

(4)  After  any  displacement  of  the  pendulum  itself  from  its 
normal  position  due  to  the  sudden  movement  or  lurch  of  the  aero- 
plane, the  pendulum  will  at  once  tend  to  swing  back  to  the 'normal. 
If  the  period  of  this  swing  should  ju^st  happen  to  coincide  with  the 
frequency  of  any  vibration  or  sway  in  the  machine  or  with  any 
wave  pulsations  of  the  air  stream,  then  the  swinging  would  continue 
and  be  amplified,  eventually  destroying  the  equilibrium  of  the 
machine.  Synchronism  of  ^this  sort  is  not  at  all  unlikely  to  happen 
for  air  waves  are  known  to  possess  pulsations  at  regular  time  inter- 
vals; and  in  addition,  propellers  have  often  been  found  to  give  con- 
tinuously and  rhythmically  varying  thrusts,  causing  a  slow  sway- 
ing vibration  in  the  aeroplane  quite  distinct  from  the  vibration  of 
the  motor. 

It  appears,  therefore,  that  the  use  of  a  pendulum  for  preserving 
the  lateral  stability  of  an  aeroplane  is  limited  in  its  action  to  the  con- 
dition of  comparatively  steady,  horizontal  flight,  and  is  hardly  feasi- 
ble in  very  gusty  weather.  A  pendulum  device,  designed  to  act  as 
a  relay,  setting  in  operation  an  electrical  apparatus  which  causes  an 
increase  or  decrease  in  the  thrust  of  the  screws  of  a  fernr-propeller 
type  of  helicopter  machine,  was  patented  in  this  country  as  far  back 
as  1888,  and  many  others  of  a  similar  nature  have  been  patented 
since. 

All  of  the  foregoing,  however,  is  to  a  very  large  extent  based 
upon  the  theory  of  the  pendulum's  action  under  the  varying  condi- 
tions in  question,  and  is  merely  the  result  of  the  author's  study  of 
this  phase  of  the  subject  from  a  theoretical  point  of  view.  That 
the  conclusions  reached  are  not  well  substantiated  in  practice 
will  be  evident  from  the  following  excerpt  from  a  letter  written 
by  Orville  Wright  to  the  author,  calling  attention  to  the  fact 
that  his  experience  with  the  pendulum  was  quite  to  the v  contrary. 
He  says: 

We  have  always  considered  a  pendulum  theoretically  an  almost  perfect 
system  for  lateral  balance.  If  the  vertical  rudder  of  a  flying  machine  is  turned 
so  as  to  face  the  machine  towards  the  left,  the  momentunTSr  centrifugal  force 
of  the  pendulum  will  cause  it  to  swing  to  the  right-hand  side.  This  will  cause 
the  wings  to  be  warped  until  the  machine  is  banked  enough  to  bring  the  pendu- 
lum at  right  angles  to  the  planes,  which  is  exactly  the  bank  the  planes  should 


464 


AERONAUTICAL   PRACTICE  23 

take  in  making  a  turn.  Not  only  is  this  theoretically  the  case,  but  in  all  of  our 
experiments  with  our  lateral  stabilizing  device  this  fact  has  been  conclusively 
demonstrated. 

There  are  pendulum-operated  stabilizing  devices  in  use  in  which  it  is 
necessary  for  the  operator  to  make  adjustments  in  order  to  give  the  machine 
a  proper  bank  in  turning,  but  this  is  not  due  to  a  fault  of  the  pendulum  but  to 
other  devices  which  have  been  incorporated  with  the  pendulum  in  the  stabiliz- 
ing system.  The  Ellsworth  lateral  stabilizer  is  one  of  this  type.  Theoretic- 
ally it  would  operate  only  in  straight  flight  and  could  not  make  a  turn  with- 
out special  adjustments  by  the  operator.  I  have  recently  made  some  flights 
with  a  new  lateral  stabilizing  device,  in  which  the  pendulum  is  used  and,  by 
simply  setting  the  top  lever  of  our  machine  slightly  to  one  side,  the  device 
banks  the  machine  for  turning  and  holds  it  at  the  proper  bank  without  any 
assistance  from  the  operator.  The  fact  that  the  pendulum  does  give  a  proper 
bank  to  a  machine  in  making  a  turn,  I  consider  to  be  its  principal  virtue.  For 
theoretical  reasons  I  have  always  considered  gyroscopic  devices  inefficient  for 
fore-and-aft  control.  I  hold  to  the  theory  that  true  stabilizing  devices  should 
be  dependent  on  the  wind.  Assuming  a  case  where  a  machine  is  flying  with 
the  least  power  that  can  possibly  sustain  it  at  its  most  favorable  angle  of  inci- 
dence, any  device  that  operates  purely  with  reference  to  the  vertical  or  hori- 
zontal, will  cause  it  to  fly  at  a  different  angle  in  case  it  runs  into  a  rising  or 
descending  trend. 

I  also  noticed  some  reference  to  an  automatic  device,  which  I  took  with 
me  and  was  intending  to  try  at  Kitty  Hawk  (October,  1911,  experiments). 
This  was  an  automatic  device  for  fore-and-aft  equilibrium,  and  is  not  the  one 
described  in  our  patent  of  several  years  ago.  I  did  not  try  it  on  account  of  the 
presence  of  the  newspaper  men  at  Kitty  Hawk.  I  have  had  one  of  the  power 
machines  here  equipped  with  the  device,  and  expect  very  soon  to  test  it  out 
thoroughly. 

AUTOMATIC  STABILIZERS 

Eteve  Stabilizer.  A  number  of  experiments  have  been  made 
with  devices  designed  to  give  automatic  longitudinal  stability  alone, 
one  of  these — the  invention  of  Captain  Eteve,  of  the  Sapper  balloon- 
ist battalion  of  the  French  army — having  been  put  to  numerous  tests 
in  actual  practice.  The  machine  itself  was  a  Wright  biplane  of 
French  construction,  the  usual  rear  rudder  of  the  original  Wright 
type  of  machine  being  replaced  by  two  hexagonal  planes  borne  on  a 
special  stabilizer  framework  and  controlled  by  spring-held  cables. 
As  shown  by  the  sketch,  Fig.  20,  the  two  planes  A  and  B  are  mov- 
able on  the  axis  E,  the  latter  being  carried  by  a  framework  about 
15  feet  long,  attached  to  the  transverse  members  of  the  aeroplane 
surfaces.  A  horizontal  vane  D,  movable  on  an  axis  F,  is  connected 
to  the  planes  A  and  B  by  rods  KJ  and  KL.  The  axis  of  the  vane  is 
firmly  fixed  to  a  tube  H,  controlled  by  the  rod  M I  through  a  bell 


465 


24 


AERONAUTICAL  PRACTICE 


crank,  MHF,  this   rod  being  in  turn  operated  by  a  lever  maneu- 
vered by  the  pilot. 

When  the  lever  is  fixed,  axis  F  is  immovable  and  the  stabilizer 
vane  struck  by  the  wind  moves  sensibly  in  the  belt  or  layer  of  wind 
immobilizing  the  planes  A  and  B,  which  are  compensated;  the 
angle  of  attack  of  these  planes  is  then  invariable  when  the  direction 
of  the  air  current  is  constant,  Fig.  21  A.  But  when  this  latter  varies, 
the  movement  of  the  vane  is  modified  and  the  planes  A  and  B  turn 
in  a  direction  contrary  to  that  of  the  vane. 


Fig.  20.     Detail  Diagrams  of  Etevc  Stabilizer 

Should  the  aeroplane  "rear,"  Fig  2 IB,  the  vane  D  is  tilted  and 
causes  the  planes  A  and  B  to  turn  in  a  direction  contrary  to  their 
proper  movement.  This  tends  to  correct  or  straighten  out  the  aero- 
plane; when  it  "plunges,"  Fig  2 1C,  the  reverse  effect  is  produced 
and  the  maneuver  is  executed  without  interference  owing  to  the 
simplicity  of  the  mechanism,  a  quality  indispensable  to  an  automatic 
stabilizer.  It  will  be  noted  that  the  Eteve  device  does  not  depend 
upon  any  external  source  of  power  but  is  operated  by  the  action  of 
the  wind  itself. 

The  planes  A  and  B,  considered  as  depression  rudders,  auto- 
matically partake  of  the  same  movements  as  those  resulting  from 


466 


AERONAUTICAL   PRACTICE  25 

the  maneuver  made  by  the  pilot;  moreover,  the  vane  has  the  advan- 
tage over  the  aviator  of  acting  simultaneously  with  the  cause  that 
produces  the  disturbance  of  equilibrium.  In  a  word,  the  Eteve 
stabilizer  opposes  all  variations  of  the  angle  of  attack  of  the  aero- 
plane in  the  same  manner  as  a  very  long,  light,  and  instantaneously- 
acting  empennage  (tail)  would.  Of  course,  it  is  necessary  to  be  able 
to  vary  the  magnitude  of  the  angle  of  attack  in  order  to  climb  or 
descend.  To  preserve  the  automatic  action  of  the  stabilizer  prior 
to,  during,  and  after  the  execution  of  the  maneuver  by  the  pilot, 
the  axis  F  of  the  vane  can  be  raised  or  lowered  by  means  of  a  lever 
under  the  control  of  the  aviator,  as  in  the  Wright  apparatus  already 


PLANE  AB 


AXIS 


W/ND 


D 
POSITION  of  EQUILIBRIUM  "  '  THE  MACHINE  REARS ' 


^ POSITION  °r  EQUILIBRIUM 

MACHINE  DIPS  WITH  LARGE  ANGLE  or  ATTACK 


C 


0 


POSITION   or  EQUILIBRIUM 
\  WITH  -SMALL  AF/GLE  or  ATTACK 

E 

Fig.  21.     Control  Action  of  Eteve  Stabilizer  under  Different  Conditions 

described.  All  displacement  of  F  involves  a  change  of  equilibrium 
of  the  vane  and  consequently  a  modification  of  the  angle  of  attack 
of  the  planes  A  and  B.  (Note  positions  D  and  E,  Fig.  21.)  This 
indirect  control  of  the  stabilizer  offers  the  great  advantage  of  render- 
ing the  vane  sensitive  to  exterior  influences,  the  apparatus  playing 
the  role  of  depression  rudder  and  stabilizer  at  the  same  time. 

The  weight  of  the  entire  stabilizer  tail  is  60.5  pounds,  which, 
less  the  vertical  rudder  it  displaces,  only  places  an  additional  weight 
of  26.5  pounds  on  the  machine.  The  total  surface  of  the  stabilizer 
planes  is  43  square  feet,  or  half  the  surface  of  the  depression  rudder 


467 


26  AERONAUTICAL   PRACTICE 

of  the  Wright  aeroplane.  The  numerous  experimental  flights  made 
with  the  machine  thus  fitted  demonstrated  the  important  role  played 
by  the  stabilizer.  First,  preliminary  attempts  were  made  to  verify 
the  equilibrium  of  the  modified  aeroplane,  the  operation  of  the  appa- 
ratus then  being  tried  out  by  running  on  the  ground.  Next,  flights 
of  a  quarter  to  half  a  mile  with  turns  were  made;  then  a  flight  of  10 
minutes  was  made  which  showed  that  the  ordinary  Wright  machine 
can  be  thus  readily  controlled.  The  operation  of  the  depression 
rudder  was  found  to  be  considerably  simplified,  and  despite  the  large 
surface  of  the  depression  rudder  of  the  Wright  machine,  the  stability 
was  such  that  the  apparatus  frequently  remained  in  equilibrium  for 
some  minutes  without  the  intervention  of  the  aviator. 

Gyroscopic  Stabilizers.  The  consideration  of  the  different  types 
of  automatic  controllers  already  discussed  leads  to  a  conclusion 
which  is  almost  self-evident.  The  same  cause  always  produces  the 
same  result  and  hence,  when  an  aeroplane  is  tipped  to  one  side,  if  it 
is  turned  back  to  its  proper  level  by  the  action  of  the  air  due  to  its 
change  of  velocity  or  angle  of  flight  through  the  air  in  that  direc- 
tion, then,  when  an  equal  change  in  angle  of  flight  or  speed  through 
the  air  is  caused  by  some  gust  striking  the  machine,  the  aeroplane 
will  be  affected  in  a  similar  manner.  For  instance,  when  an  aero- 
plane in  stable  equilibrium  turns  upward,  its  speed  through  the  air 
is  diminished  and  the  front  drops  to  the  proper  level,  but  when  a 
wind  strikes  it  from  behind,  its  speed  through  the  air  is  likewise 
diminished  and  the  front  will  again  drop,  but  this  time  away  from 
the  proper  angle  of  flight.  Therefore,  since  it  is  found  that  the  sta- 
bility of  all  machines  balanced  in  a  manner  similar  to  those  above 
described  must  depend  upon  the  machine's  reaction  with  the  air, 
no  such  system  of  automatic  equilibrium  can  be  depended  upon  to 
preserve  perfect  balance  while  the  aeroplane  sails  through  the  cur- 
rents and  cross  currents  met  with  in  practically  every  flight. 

True  Stabilizer  Independent  of  Wind  Changes.  It  is  essential, 
therefore,  that  the  controller  shall  be  sensitive  not  to  the  force  or 
direction  of  the  wind  that  strikes  the  machine,  but  to  some  other 
force  which  will  move  the  controller  with  respect  to  the  aeroplane 
when  its  equilibrium  is  disturbed.  The  only  such  forces  known  are 
that  of  the  earth's  magnetic  field  acting  on  a  magnetic  needle,  and 
the  gyroscopic  force  of  a  rapidly  rotating  wheel.  The  magnetic 


468 


AERONAUTICAL   PRACTICE  27 

needle  is  usually  employed  merely  to  indicate  the  north,  but  since 
the  earth's  magnetic  field  tends  to  make  it  dip  downward  at  an  angle 
of  about  75  degrees  with  the  horizon,  and  since  this  angle  is  constant 
in  any  locality,  if  the  direction  of  flight  be  fixed,  the  magnet  may 
be  employed  to  determine  a  horizontal  position.  It  may  be  made  to 
operate  the  controlling  planes  through  the  medium  of  electromag- 
nets acting  to  open  and  close  the  valves  of  a  compressed-air  motor. 
Since  both  arms  of  the  magnet  have  the  same  mass,  neither  gravity 
nor  centrifugal  force,  due  to  the  oscillations  of  the  aeroplane,  would 
affect  it  in  any  way,  but  the  slightest  vibration  once  started  would 
continue  indefinitely  and  thus  be  transmitted  to  the  control  of  the 
aeroplane.  Also  in  making  turns,  since  the  needle  points  downward 
at  an  angle  of  75  degrees,  instead  of  90  degrees,  there  would  be  dan- 
ger of  losing  balance.  So,  aside  from  the  prohibitive  frailness  of  the 
construction,  the  magnetic  needle  would  not  make  a  suitable  con- 
trolling device.  It  is  therefore  necessary  to  examine  what  can  be 
accomplished  with  the  aid  of  the  gyroscope. 

Gyroscopic  Action.  It  is  a  well-known  fact  that  a  rapidly 
spinning  top  forcibly  resists  any  attempt  to  change  its  plane  of  rota- 
tion. This  force  depends  upon  the  weight  at  the  periphery  of  the 
revolving  body  and  its  speed  of  rotation.  The  top  is  a  gyroscope 
in  its  simplest  form,  and  by  giving  it  the  form  of  a  flywheel  with  a 
heavy  rim  we  have  the  toy  that  is  doubtless  familiar  to  most  boys — 
the  gyroscopic  top.  In  this,  the  diminutive  flywheel  is  supported 
on  a  spindle  carried  in  a  circle  of  wire  in  order  to  provide  a  means  of 
support  independent  of  the  spindle  itself.  When  spinning  rapidly, 
such  a  top  will  continue  to  rotate  in  any  plane  in  which  it  is  placed, 
horizontally,  vertically,  or  at  any  angle  between  the  two.  This  singu- 
larly curious  force  was  first  applied  industrially  in  1870.  Since  then 
the  progress  achieved  in  its  use  has  been  comparatively  slow.  It 
has  been  employed  for  securing  much-needed  stability  to  the  Beau- 
champ  hydraulic  turret,  the  Obry  torpedo,  the  Scherl,  Brennan,  and 
Froelich  monorail  systems  of  transportation,  and  to  Schlick's  device 
for  preventing  the  rolling  of  a  ship. 

Widespread  interest  now  attaches  to  its  employment  in  a  similar 
role  on  the  aeroplane.  In  this  connection,  however,  the  distinction 
between  equilibrium  and  stability  should  be  borne  in  mind  as  the 
terms  are  so  frequently  used  interchangeably  as  to  prove  confusing. 


469 


28  AERONAUTICAL   PRACTICE 

Briefly  stated,  an  aeroplane  is  in  equilibrium  when  traveling  at  a 
uniform  rate  of  speed,  and  it  is  necessary  for  stability  that,  if  the 
aeroplane  is  not  in  equilibrium  and  be  not  moving  uniformly,  it 
shall  tend  toward  a  center  of  equilibrium,  also  that  any  oscillatory 
motion  shall  have  a  positive  coefficient  of  subsidence.  A  thorough 
study  of  the  different  forms  of  machines  made  by  a  close  observer 
led  him  to  the  conclusion  that  the  only  two  types  likely  to  prove 
stable  under  ordinary  conditions  are  the  single-surface  glider  and 
the  balanced  glider.  The  first,  as  he  expressed  it,  relies  for  its  longi- 
tudinal stability  on  the  variation  of  the  center  of  pressure  with  the 
angle  of  attack,  while  the  second  relies  on  the  variation  in  altitude 
of  a  balancer  or  tail  surface.  In  each  case,  a  torque  should  come 
into  existence  to  bring  the  glider  back  to  its  original  position.  With 
these  types,  however,  as  they  now  stand,  a  very  severe  squall  is 
likely  to  prove  disastrous ;  for  the  righting  of  the  machine  can  not  be 
made  rapidly  enough.  There  must  necessarily  be  an  automatic 
adjustment  to  secure  the  equilibrium  of  all  the  planes. 

Regnard  Device.  To  bring  about  this  automatic  adjustment, 
numerous  inventors  are  looking  to  the  gyroscope  as  a  solution  of  the 
problem,  one  of  the  first  machines  to  be  equipped  with  it  being  the 
Regnard  monoplane.  The  details  of  the  aeroplane  in  plan  and  ele- 
vation are  shown  in  Fig.  22,  while  the  gyroscope  and  its  mounting 
are  given  in  Fig.  23.  In  this  case,  the  small  and  comparatively  light 
gyroscope  used  is  not  directly  employed  to  insure  stability.  It  merely 
serves  to  transmit  an  electrical  current  to  devices  for  giving  both 
lateral  and  longitudinal  stability.  The  gyroscope  itself,  A,  Fig.  22, 
is  located  directly  beneath  the  center  of  the  main  supporting  sur- 
face I  and  in  line  with  the  motor.  It  is  hung  on  gimbals — i.e.,  a 
universally- jointed  support,  Fig.  23,  permitting  complete  indepen- 
dence and  freedom  of  movement.  Within  the  ring  A  of  this  gyro- 
scope is  the  flywheel  T  and  the  ring  armature  C  of  a  small  electric 
motor  to  which  it  is  directly  coupled  at  its  lower  end. 

The  stationary  field  L  of  the  motor  is  also  of  the  ring  type  and 
lies  in  the  same  plane  as  the  armature  it  encloses.  Current  from 
eight  or  ten  storage  cells  of  about  the  size  ordinarily  employed  in 
electric  vehicles,  maintains  the  flywheel  in  rotation  at  a  speed  of 
10,000  r.  p.  m.  According  to  well-known  laws  of  mechanics,  it  will 
adopt  under  the  influence  of  this  rotative  speed  an  invariable  plane, 


470 


AERONAUTICAL   PRACTICE 


29 


parallel  to  the  plane  of  the  space  wherein  it  is  hung — a  horizontal 
plane  in  this  case.  Owing  to  its  method  of  support  it  will  take,  with 
reference  to  the  aeroplane,  all  the  relative  positions  corresponding 
to  the  inclination  of  the  latter.  In  other  words,  the  gyroscope  will 


Fig.  22.     Detail  Diagrams  of  Regnard  Gyroscopic  Stabilizer 

continue  to  revolve  in  its  horizontal  plane,  while  its  frame,  attached 
to  the  aeroplane,  will  assume  different  positions  relative  to  it  in  ac- 
cordance with  the  angle  of  inclination  of  the  machine,  i.e.,  the  gyro- 
scope remains  stationary  while  its  support  moves  about  it  as  a  fixed 


471 


30 


AERONAUTICAL  PRACTICE 


point.  In  doing  so,  the  stud  E,  rigidly  attached  to  the  gyroscope, 
establishes  electric  contact  with  the  plates  F,  according  to  the  move- 
ments of  the  aeroplane.  Each  of  these  contacts  is  alternately 
employed  for  controlling  and  steadying  the  movements  of  one  or 
more  of  the  surfaces  of  the  aeroplane. 

These  contacts  can  be  made  in  a  number  of  different  ways — 
by  way  of  example,  as  shown  in  the  upper  and  lower  diagrams  of 

Fig.  23,  through  the  me- 
dium of  the  conducting 
plates  a  and  6,  which 
are  superposed  but  not 
touching.  The  upper 
plate  a  has  a  projection 
c  on  which  the  stud  E 
will  press,  the  convex 
surface  of  the  latter  al- 
ways corresponding  to 
the  center  of  rotation  of 
the  gyroscope.  Regard- 
less of  the  inclination  of 
the  aeroplane  the  axis  of 
E  is  always  vertical,  and 
in  whatever  direction  the 
machine  cants,  it  will 
press  momentarily  upon 
the  plate  a,  the  latter 
then  coming  in  contact 
with  b.  The  circuit 
thus  established  can  be 
utilized  for  specially  con- 
trolling any  one  or  more 
of  the  balancing  organs 
of  the  aeroplane.  In  the 
present  instance,  this  is 

effected  by  means  of  solenoids,  or  hollow  electromagnets,  in  which  soft 
iron  plungers  slide.  Two  of  these  solenoids,  G  and  Gf,  are  employed, 
adapted  to  be  energized  in  alternate  directions  by  means  of  two 
sets  of  contacts,  Fl  and  F2,  for  the  longitudinal  balance,  and  F3  and 


Fig.  23.     Gyroscopic  Control-Device  of  Regnard 
Stabilizer 


472 


AERONAUTICAL   PRACTICE  31 

F±  for  the  lateral  balance.  For  instance,  should  a  strong  gust  of  wind 
cause  the  aeroplane  to  tilt  downward,  E  will  instantly  make  contact 
with  Flt  energizing  the  solenoid  G.  The  plunger  of  the  latter  is  suitably 
connected  by  means  of  a  cable  to  the  elevating  rudder  H  and  the 
pull  exerted  by  the  solenoid  will  vary  its  angle  of  attack  downward, 
thus  righting  the  machine,  or  bringing  it  to  an  even  keel.  In  case  of 
the  reverse  inclination — the  tendency  of  the  aeroplane  to  stand  on 
its  tail — the  solenoid  G  will  again  come  into  action  through  the 
contact  F2,  but  the  plunger  will  move  in  the  other  direction  due 
to  a  reversal  of  the  current,  and  the  elevating  rudder  will  be 
moved  to  the  opposite  angle,  again  bringing  the  machine  down  to 
an  even  keel,  or  horizontal  plane.  Transverse  control  is  maintained 
in  a  similar  manner,  an  inclination  to  either  side  causing  the  sole- 
noid G'  to  come  into  action  in  one  direction  or  the  other  through  the 
contacts  F3  and  F4,  according  to  the  movement  of  the  aeroplane 
itself.  The  plunger  of  this  solenoid  is  connected  through  suitable 
multiplying  gear  and  cables  to  the  warping  apparatus  of  the  wings. 
It  will  be  noted  that  this  device  is  practically  similar  in  its 
operation  to  the  Wright  apparatus,  except  that  a  gyroscope  is 
employed  as  an  automatic  governing  control  in  place  of  the  vane 
and  pendulum  of  the  latter,  and  electric  power  is  employed  instead 
of  compressed  air.  In  other  words,  both  devices  merely  relieve  the 
aviator  of  the  constant  necessity  of  manually  operating  the  usual 
controls  for  maintaining  longitudinal  and  lateral  stability — the 
elevating  rudder  and  the  wing-warping  levers.  There  is  nothing 
unusual  about  ttye  Regnard  apparatus  electrically  or  mechanically, 
except  the  automatic  method  of  making  contact  by  means  of  the 
gyroscope,  the  action  of  a  solenoid  being  commonly  utilized  to 
operate  such  electrical  apparatus  as  circuit  breakers  and  the  like. 
However,  the  efficiency  of  a  solenoid  is  comparatively  low;  it  requires 
considerable  current  to  cause  it  to  generate  an  appreciable  amount 
of  power  and  to  act  quickly.  With  such  a  limited  source  of  power 
as  the  storage  cells  mentioned,  the  solenoids  would  have  to  be  pro- 
hibitively heavy.  Of  course,  a  dynamo  could  be  run  by  the  motor 
of  the  aeroplane  itself,  but  this  likewise  involves  considerable  extra 
weight.  Moreover,  while  an  apparatus  such  as  that  described  would 
be  considered  simple  for  an  electric  lighting  station  or  similar  instal- 
lation, it  involves  an  excessive  amount  of  complication  for  an  aero- 


473 


32  AERONAUTICAL   PRACTICE 

plane — there  would  be  entirely  too  many  small  things  to  look  after 
and  keep  in  order.  Using  a  generator  directly  attached  to  the  gaso- 
line motor  and  two  small  electric  motors  instead  of  the  solenoids, 
would  simplify  the  apparatus  somewhat  and  make  it  much  more 
powerful  for  its  weight,  but  still  there  would  be  entirely  too  much 
unnecessary  weight  to  carry  along.  The  attempt  is  interesting  as 
illustrating  what  may  be  done,  but  there  are  doubtless  few  aviators 
who  would  not  prefer  to  rely  upon  their  skill  in  manually  operating 
the  controls  rather  than  have  the  machine  encumbered  with  so 
much  apparatus,  particularly  as  some  means  of  cutting  out  its  action 
when  desiring  to  ascend  or  descend  would  also  have  to  be  provided, 
as  mentioned  in  connection  with  both  the  Wright  and  Eteve  stabil- 
izing devices. 

Beach  Device.  Utilizing  the  controlling  force  of  the  gyroscope 
direct  would  appear  to  hold  forth  much  greater  promise  of  simplicity 
and  reliability  in  action.  This  was  attempted  during  1910  by 
an  American,  Stanley  Y.  Beach,  the  aeronautical  editor  of  the 
Scientific  American.  The  gyroscope  in  this  case  is  a  flywheel  weigh- 
ing about  20  pounds  and  is  designed  to  revolve  in  a  vacuum  at  10,000 
r.p.m.  The  complete  apparatus  weighs  about  30  pounds.  The 
gyroscope  itself  is  illustrated  in  Fig.  24,  while  its  location  and  method 
of  attachment  to  a  Beach  monoplane  (Bleriot  type)  is  shown  at  the 
bottom  of  Fig.  25.  The  flywheel  is  driven  through  bevel  gears  so 
that  it  runs  about  three  times  as  fast  as  the  driving  pulley  on  the  hor- 
izontal shaft.  The  spindle  projecting  out  at  the  top,  Fig.  24,  passes 
down  through  a  long  bushing  about  6  inches  in  length  and  drives 
a  short  shaft  at  the  bottom  through  a  ratchet  attachment.  It  is  in 
fact,  a  friction  drive,  the  details  of  which  are  not  as  yet  protected 
by  patents,  for  which  reason  they  are  not  given  here. 

To  obtain  the  vacuum,  which  makes  necessary  only  a  fraction 
of  a  horse-power  to  drive  the  flywheel,  a  small  vacuum  pump,  about 
the  size  of  the  ordinary  bicycle  pump,  is  attached  by  means  of  a 
short  rubber  tube  to  a  pet  cock  at  the  apex  of  the  conical  housing. 
The  air  can  be  exhausted  from  this  housing  with  the  pump  in  ques- 
tion in  about  five  minutes,  and  the  leakage  about  the  stuffing  box 
of  the  spindle  is  so  slight  that  the  vacuum  is  maintained  for  almost 
twenty-four  hours.  The  only  object  of  employing  a  vacuum  is  to 
minimize  the  amount  of  driving  power  necessary,  it  having  no  effect 


474 


AERONAUTICAL   PRACTICE 


33 


one  way  or  the  other  upon  the  gyroscope  or  its  action.  When  driven 
in  the  air,  two  or  three  times  as  much  power  is  required  and  it  takes 
a  great  deal  longer  to  get  the  flywheel  up  to  speed  owing  to  the  resist- 


Fig.  24.     Beach  Gyroscopic  Stabilizer 

ance.  With  a  vacuum,  on  the  other  hand,  only  about  fifteen  min- 
utes are  necessary  for  it  to  attain  a  speed  of  10,000  r.p.m.  and  it  will 
then  continue  to  run  for  one  and  a  half  to  two  hours  without  any 
further  application  of  power. 


475 


34  AERONAUTICAL  PRACTICE 

When  the  aeroplane  tends  to  tilt  to  either  side,  the  gyroscope 
will  resist  this  inclination  with  a  force  of  900  pounds  at  a  distance 
of  1  foot  from  the  center  of  the  flywheel.  At  the  same  time,  as  the 
aeroplane  inclines  slightly  to  one  side  or  the  other,  the  gyroscope 
will  tilt  forward  or  backward,  as  the  case  may  be.  To  permit  of 
overcoming  this  force  of  the  gyroscope,  when  not  desired,  a  band 
brake  acting  on  a  drum  on  the  shaft  (not  shown  in  the  illustration) 
is  employed.  This  locks  the  gyroscope  and  prevents  its  performing 
its  act  of  precession,  as  it  is  technically  termed.  In  this  condition 
its  resistance  is  practically  negligible  and  applying  this  brake  allows 


Fig.  25.     Beach  Gyroscopic  Stabilizer  Mounted  in  an  Aeroplane  Frame 

the  aeroplane  to  "bank"  in  rounding  a  turn  by  means  of  the  trans- 
verse warping  control  as  is  customarily  done.  Should  the  aviator 
neglect  to  apply  this  brake  before  attempting  to  make  a  turn, 
however,  no  harm  will  result,  as  the  machine  will  then  simply 
remain  on  a  level  keel  and  "skid"  or  slide  toward  the  outer  circum- 
ference of  the  curve  it  is  making,  under  the  action  of  centrifugal 
force.  Fig.  24  shows  the  complete  gyroscope  mounted  in  a  frame 
corresponding  to  its  support  on  the  aeroplane,  this  frame  being 
tipped  to  represent  the  inclination  of  the  flyer  to  the  right.  It  is 
being  driven  at  its  usual  high  speed  as  shown  here  and  the  forward 
tilt  of  the  apparatus  is  noticeable,  though  this  does  not  appear  to 


476 


AERONAUTICAL  PRACTICE  35 

be  as  great  as  it  is  in  reality.  When  tried  on  a  monoplane  running 
over  the  ground,  this  gyroscope  gave  a  perceptibly  steadying  effect, 
though  not  running  at  more  than  half  its  normal  speed. 

Doutre  Stabilizer.  This  is  a  type  that  differs  more  or  less  rad- 
ically from  any  of  those  already  mentioned.  It  has  been  put  to 
severe  tests  by  the  army  in  both  France  and  Russia  and  has  showed 
unusually  promising  results.  The  apparatus  consists  of  two  ele- 
ments, each  fulfilling  a  distinct  function.  The  first  of  these  is, 
properly  speaking,  an  anemometer  whose  purpose  is  to  detect  changes 
in  the  wind  pressure;  the  second  element  constitutes  an  acceler- 
ometer,  its  function  being  to  detect  and  respond  to  changes  in  the 
velocity  of  the  aeroplane.  These  two  elements  are  so  arranged  as 
to  act  either  separately  or  jointly,  according  to  exigencies,  upon  the 
mechanism  controlling  the  elevating  rudder  at  the  front  of  the  aero- 
plane. The  anemometer,  which  is  shown  in  diagrammatical  repre- 
sentation in  Fig.  26  and  in  greater  detail  in  Fig.  27,  comprises  a  plate 
P,  mounted  on  four  rods  T,  con- 
nected with  two  tubes  A  which 
slide  smoothly  in  an  aluminum 
body  S.  Springs  R2  oppose  the 
tendency  of  the  air  to  force  back 

the  plate  P,  when  the  latter  is    AftAA/       U/UA  AAAA< 

moving  in  a  direction  from  left  /?,    I       \   /?,  /?* 

to  right.     The  strength   of  the 

Fig.  26.     Diagram  of  Doutre  Stabilizer 

springs  is  so  adjusted  that  when 

the  relative  wind  pressure  is  equal  to  or  greater  than  that  required 
to  sustain  the  aeroplane,  the  springs  R2  are  compressed  to  their 
limit  and  the  tubes  A  thrust  back  against  a  shoulder  upon  the 
aluminum  casing.  If  the  pressure  of  the  wind  falls  below  this  value, 
the  springs  7^  act  on  the  weights  M,  which  in  turn,  through  the  pins 
0,  thrust  forward  the  rods  E.  These  latter  rods  are  rigidly  con- 
nected with  the  sliding  piston  rod  N  of  an  auxiliary  motor,  the  cylin- 
der C  of  which  receives  through  the  chamber  D  compressed  air  act- 
ing upon  the  piston  Blf  There  is  no  need  to  enter  into  detailed 
description  of  the  auxiliary  motor,  the  principle  of  which  is  well 
known;  air  is  admitted  into  the  compartments  H  and  7,  according 
as  the  displacement  of  the  piston  rod  N  opens  or  closes  the  admis- 
sion port  shown  in  dotted  lines.  The  surplus  air  escapes  through 


477 


36 


AERONAUTICAL  PRACTICE 


openings  at  the  end  of  the  rod  N,  or  the  piston  Blf  as  the  case  may 
be.  Every  displacement  of  N  is  immediately  followed,  in  conse- 
quence of  the  arrangement  described,  by  a  displacement  in  the  same 
direction  of  the  piston  B^  This  latter  actuates  the  rudder  through 
a  pivoted  point  B2 . 

So  far  the  control  of  the  rod  N  by  the  springs  #2  has  been 
described.  But  there  is  a  second  control,  which  is  effected  by  the 
two  weights  M .  These  are  ordinarily  kept  stationary  by  the  springs 
RI.  But  if  the  aeroplane  makes  a  sudden  plunge,  the  inertia  of  the 
weights  causes  them  to  lag  behind  the  motion  of  the  body  of  the 
machine;  thus  there  is  a  relative  motion  of  the  weights  M  in  regard 
to  the  tubes  A  upon  which  they  slide,  a  motion  which  is  directed 


Fig.  27.     Detail  Section  of  Doutre  Stabilizer 

either  forward  or  backward  according  as  the  acceleration  of  the 
machine  is  negative  or  positive.  These  movements  of  the  weights 
are  transmitted  to  the  rods  E  by  the  pins  0,  and  thus  react  on  N  and 
the  auxiliary  motor  much  in  the  same  way  as  the  plate  P.  A  force 
of  100  grams  weight  (3.2  ounces)  is  sufficient  to  affect  the  appara- 
tus, while  the  auxiliary  motor,  which  receives  its  air  supply  from 
the  aeroplane  motor,  readily  gives  a  thrust  of  10  to  30  kilograms 
(22  to  66  pounds) .  This  is  more  than  sufficient  to  operate  the  rudder. 
The  anemometer  plate  and  the  accelerometer  weights  both  act 
independently  and  simultaneously  upon  the  elevating  rudder.  Their 
effect  is  either  added  or  opposed,  according  to  the  conditions  of 


478 


AERONAUTICAL   PRACTICE  37 

flight,  and  the  whole  is  adjusted  so  as  to  give  the  proper  steering 
upon  the  rudder.  Since  each  variation  in  the  angle  of  the  rudder 
brings  about  a  variation  in  the  aeroplane  speed,  the  apparatus  acts 
to  correct  the  effect  of  its  own  action  on  the  rudder,  even  while  this 
is  taking  place.  It  is  also  to  be  noted  that  the  apparatus  does  not 
wait  to  act  until  the  aeroplane  has  taken  a  false  movement,  but  it 
acts  directly  under  the  shock  which  also  tends  to  act  upon  the  aero- 
plane, thus  taking  account  of  the  cause  itself  and  not  the  effect. 
The  correction  given  to  the  rudder  is  thus  very  quick.  The  move- 
ment of  the  main  rod  of  the  apparatus  is  transmitted  to  the  rudder 
in  a  very  simple  way  by  the  use  of  compressed  air,  the  air  being 
furnished  by  a  small  compressor  driven  from  the  aeroplane  motor 
itself.  The  compressed  air  piston  device  is  operated  by  the  main 
rod,  and  the  piston  movement  is  transmitted  in  a  suitable  way  to 
the  rudder,  independent  of  the  pilot's  levers.  The  pilot  can  work  the 
rudder  himself  or  he  can  remove  his  hands  from  the  levers  and  allow 
the  automatic  device  to  do  the  steering,  at  least  for  a  short  time. 

Trials  of  the  Doutre  stabilizer  have  shown  it  to  be  so  sensitive 
in  action  that  the  pilot  has  removed  his  hands  from  the  levers  while 
the  machine  was  still  rolling  on  the  ground,  and  the  automatic 
apparatus  has  assumed  control  of  the  aeroplane  causing  it  to  rise, 
the  operator  again  taking  hold  after  reaching  an  elevation  of  60 
feet.  The  aeroplane  was  then  sent  up  to  a  height  of  1,000  feet,  and 
again  entrusted  to  the  stabilizer,  the  pilot  keeping  his  hands  on  the 
levers,  but  not  working  them.  It  was  noted  that  the  small  plate 
kept  up  a  slight  (beating  movement,  working  back  and  forth  over 
some  three  inches,  as  an  indicating  pointer  showed;  the  rudder 
followed  up  this  slight  movement,  so  that  the  flight  was  very  steady. 
The  levers  moved  somewhat  under  the  action  of  the  apparatus, 
despite  the  fact  that  the  pilot  kept  his  hands  on  them.  He  then 
raised  his  hands  for  periods  of  four  to  six  seconds,  resuming  them 
only  to  take  care  of  the  side  steering  to  avoid  a  rolling  movement. 
At  times  it  was  quite  evident  that  no  effort  was  required,  the  auto- 
matic device  doing  all  the  steering.  When  the  pilot  tried  to  oppose 
the  action  of  the  stabilizer  he  had  to  use  quite  a  little  force.  At  one 
time,  the  apparatus  was  left  to  itself  entirely  for  twelve  seconds; 
then  the  pilot  slowed  up  the  motor  several  times,  and  each  time  the 
plate  and  the  moving  weights  gave  the  right  action  to  the  rudder. 


479 


38 


AERONAUTICAL   PRACTICE 


Fig.  28.     Doutre  StabiUzer.     Action  of  M 
on  Sudden  Acceleration 


Ellsworth  Lateral  Stabilizer. 


Returning,  the  motor  was  slowed  up  and  the  aeroplane  descended 
on  a  very  good  slope  and  the  apparatus  always  corrected  the  descent 
so  that  it  took  place  under  the  best  conditions  right  to  the  moment 
of  landing.  The  action  is  shown  diagrammatically  in  Figs.  28,  29, 

and  30.  The  test  was  thus  very 
conclusive,  and  numerous  others 
made  subsequently  proved 
equally  satisfactory.  Three  aero- 
planes for  the  French  army  have 
been  fitted  with  the  Doutre  ap- 
paratus. 

Supplementing  the  good  results 
obtained  with  the  French  longitudinal  stabilizer  just   described   is 
an  American  device  for  maintaining  lateral   stability,    which  after 
all  is  quite  as  important,  if  not  more  so.    As  a  general  rule  a  prop- 
erly-designed   aeroplane   is    well 
balanced  longitudinally  and  does 
not    ordinarily    tend    to    pitch, 
while    its   lateral   stability   is   a 
matter  that  has  to  be  corrected 
every   few   minutes   during   the 
entire  flight.    The  device  is  the 

invention  of  a  resident  of  Portland,  Oregon,  and  is  the  first  lateral 
automatic  stabilizer  to  be  successfully  tried  out  in  practice.  The 
mechanism  consists  of  two  rotating  electromagnets  driven  in 
opposite  directions  by  a  gear.  An  armature  between  these  two 

multipolar  magnets  is  keyed  to 


a  shaft  carrying  a  drum  so  that 
any  movement  of  the  armature 
carries  the  drum  with  it.  This 
drum  carries  cables  connected 
to  the  ailerons  or  wing  tips  for 
balancing.  An  electric  circuit  is 
completed  by  an  arm  of  a  pendulum  dipping  into  a  mercury 
cup  upon  the  listing  of  the  aeroplane  to  either  side.  One  of  the 
rotating  magnets  is  then  excited  and  exerts  a  magnetic  pull  on 
the  armature,  thus  rotating  the  drum.  The  drum  shaft,  however, 
terminates  in  a  gear,  and  the  block  containing  the  mercury  contact 


Fig.  29.     Plate  P  Sets  Elevating  Rudder 
for  Descent  if  Speed  Slackens 


Fig.  30.     Motor  Breakdown  Sets  Rudder 
for  Volplaning 


480 


AERONAUTICAL   PRACTICE  39 

cup  is  so  attached  to  the  gear  wheel  that  the  rotation  of  the  latter 
will  drop  the  cup  away  from  the  pendulum  arm,  again  breaking 
the  circuit  and  leaving  the  ailerons  set  to  right  the  aeroplane.  As 
the  latter  resumes  its  normal  level  of  flight,  the  action  of  the 
stabilizer  is  reversed,  returning  the  ailerons  to  their  normal  neu- 
tral position.  Means  are  provided  which  permit  the  aviator  to 
rotate  the  block  containing  the  mercury  cups  at  will,  thus  making 
contact  for  banking  the  aeroplane  to  any  required  angle  to  round 
a  curve.  A  movement  of  the  block  does  not  cause  any  movement 
of  the  gear  wheel,  yet  a  movement  of  the  latter  causes  a  rela- 
tive movement  of  the  block.  This  permits  the  aviator  to  alter  his 
angles  laterally,  of  course,  at  will  without  in  any  way  interfering 
with  the  automatic  control.  It  can  be  applied  to  fore  and  aft,  as 
well  as  lateral,  control.  One  of  the  Ellsworth  stabilizers  was  fitted 
to  a  Curtiss  biplane  during  the  fall  of  1911,  and,  in  the  course  of  an 
extended  series  of  flights,  it  was  said  to  respond  instantly  to  the  least 
variation  from  the  horizontal  far  more  quickly  than  could  be  detected 
by  the  aviator  himself.  This  was  learned  by  having  the  wires  from 
the  ailerons  connected  to  the  steering  post,  which  was  pulled  from 
side  to  side  by  the  action  of  the  automatic  control  in  maintaining 
the  balance,  before  the  aviator  was  even  aware  that  the  balance 
had  been  sufficiently  disturbed  to  make  this  necessary.  In  turning 
corners,  the  stabilizer  banks  the  aeroplane  automatically  by  hav- 
ing the  mechanism  connected  to  and  controlled  by  the  steering 
wheel,  thereby  banking  the  machine  at  just  the  required  angle  for 
the  turn;  but  the  amount  of  this  banking  is  always  at  the  instant 
command  of  the  aviator  should  he  desire  to  make  it  more  or  less, 
and  the  automatic  balance  is  not  interfered  with  in  any  way.  The 
device  is  very  compact,  weighing  but  18  pounds,  and  is  adapted  to 
be  driven  directly  from  the  aeroplane  motor,  but  it  can  also  be 
arranged  so  as  to  be  driven  from  an  electric  motor  and  storage  bat- 
teries to  provide  against  stoppage  of  the  driving  motor,  in  which 
case  the  drive  would  automatically  be  taken  up  by  the  electric 
motor.  This  addition,  however,  would  involve  extra  complication 
and  weight  that  ordinarily  would  not  be  considered  justifiable. 

While  many  investigators  are  working  on  the  problem  of  auto- 
matic stability  as  revealed  by  the  various  devices  described  here, 
opinion  as  to  the  necessity  of  providing  any  automatic  form  of  con- 


481 


£0  AERONAUTICAL  PRACTICE 

trol  is  more  or  less  divided  at  the  present  writing.  It  seems  prob- 
able, however,  that  the  perfected  machine  of  the  future  will  embody 
this  feature,  and  that  it  will  be  of  such  a  flexible  character  as  to  per- 
mit manual  control  of  the  machine  at  all  times  and  yet  be  capable 
of  preventing  such  complete  loss  of  equilibrium  as  seems  to  have 
occurred  in  the  cases  of  Moisant,  Hoxsey,  and  Johnstone — in  other 
words,  a  self-righting  ability  analogous  to  and  approaching  as  closely 
as  possible  to  that  shown  by  the  birds  when  accidentally  capsized 
in  violent  winds.  Hoxsey's  death,  for  example,  which  is  generally 
thought  to  have  been  due  to  loss  of  consciousness  resulting  from  the 
sudden  change  of  altitude,  might  have  been  averted  by  such  a 
device  as  it  would  have  brought  the  machine  to  the  ground  without 
damage. 

ALTITUDE  AND  ITS  MEASUREMENT 

Nothing  more  strikingly  reveals  the  great  development  of 
the  aeroplane  in  a  very  short  time  and  the  absolute  command 
over  it  that  has  been  achieved,  than  the  rapidity  with  which  altitude 
records  have  followed  one  another.  It  will  be  recalled  that  the 
pioneers  of  aerial  flight  had  quite  as  much  difficulty  in  learning  to 
fly  as  they  did  in  designing  a  machine  in  which  to  accomplish  it, 
and  they  trusted  themselves  to  a  motor-driven  craft  only  after  hav- 
ing thoroughly  mastered  the  principles  of  the  art  through  long- 
repeated  practice  in  gliding.  There  was,  therefore,  nothing  strange 
in  the  fact  that  although  flight  in  a  heavier-than-air  machine  was 
actually  a  reality,  the  flyers  preferred  at  first  to  remain  close  to  the 
ground.  For  this  reason  there  was  keen  and  widespread  disappoint- 
ment among  the  spectators  who  attended  the  first  public  exhibitions 
of  flying  in  this  country  by  Farman,  the  Frenchman.  The  manner  in 
which  he  kept  close  to  the  ground,  never  exceeding  a  height  of  50  feet 
and  oftener  remaining  within  30,  was  not  at  all  satisfactory  to  the 
crowd  to  whom  the  definition  of  the  word  flying  did  not  mean  the 
ground-skimming  swoops  of  the  sparrow,  but  the  lofty  soaring  of 
the  eagle  or  larger  birds.  From  a  spectacular  point  of  view,  Farman's 
exhibition  was  an  utter  failure. 

Altitude  Records.  With  increasing  confidence,  heights  of  200 
or  300  feet  were  attained  and  at  some  of  the  earlier  French  meetings 
the  height  reached  by  the  aviator  was  determined  by  means  of  a 


482 


AERONAUTICAL   PRACTICE  41 

captive  balloon  anchored  over  the  field.  If  the  contestant  flew  above 
it,  he  surpassed  the  former  record  and  there  was  not  much  question 
of  definite  figures.  But  advancement  was  so  rapid  that  this  plan 
very  soon  became  obsolete.  From  the  few  hundred  feet  that  seemed 
to  mark  the  limit  in  the  early  part  of  1908,  Morane  rose  to  2,500 
meters  or  8,202  feet  but  little  more  than  a  year  later,  September  3, 
1909.  This  eye-opening  performance  showed  what  could  be  done  and 
immediately  inspired  confidence  in  others.  Competition  was  fos- 
tered by  numerous  and  substantial  prizes  offered  for  altitude  at 
meetings,  and  one  record  followed  another,  Johnstone  reaching  a 
height  of  9,714  feet  in  a  Wright  biplane  during  the  International 
Meet  at  Belmont  Park  in  October,  1910,  and  Drexel  surpassing  this 
in  a  Bleriot  monoplane  only  a  few  weeks  later  at  Philadelphia  by 
attaining  an  altitude  of  9,897  feet.  As  this  record  stood  but  little 
more  than  a  month  before  being  raised  by  the  very  liberal  margin  of 
more  than  1,000  feet  by  Hoxsey  who  soared  to  an  altitude  of  11,474 
feet  in  California  on  December  27,  1910,  it  is  quite  apparent  that  a 
point  has  already  been  reached  where  the  matter  of  soaring  is  one 
limited  jmly  by  human  rather  than  mechanical  shortcomings.  In 
other  words,  it  seems  quite  possible  that  an  aeroplane  can  be  flown 
as  high  as  human  endurance  will  permit.  The  various  elevations 
attained  by  human  effort  are  shown  in  Fig.  31.* 

It  has  been  a  matter  of  common  knowledge  for  many  years  that 
ascending  to  great  heights  on  mountains  is  attended  by  considerable 
physical  discomfort  and  is  accompanied  by  disagreeable  physiological 
symptoms.  Some  individuals  are  peculiarly  susceptible  to  the  latter 
and  claim  to  be  affected  by  them  at  an  elevation  of  only  a  few  thou- 
sand feet.  While  mountain  climbing  offers  some  analogy  to  aero- 
plane climbing,  the  gradual  transition  from  the  heavier  to  the  lighter 
and  more  rarefied  atmosphere  permits  ample  opportunity  for  the 
body  to  accustom  itself  to  the  change.  In  contrast  with  this,  it  has 
been  common  for  aviators  to  travel  the  first  7,000  or  8,000  feet  of 
their  record-breaking  upward  flights. in  a  little  more  or  less  than  half 
an  hour.  Hoxsey  is  said  to  have  risen  the  first  9,000  feet  of  his  record 
flight  in  California  in  thirty-five  minutes.  This  is  equivalent  to 
being  transported  upward  a  mile  and  three-quarters  in  about  the 

*These  were  considerably  surpassed  in  1911,  Beachey  having  risen  well  over  12,000  feet 
at  the  Chicago  Meet  in  August,  while  French  aviators  have  also  been  making  new  altitude 
records. — Ed. 


483 


42 
$. 


AERONAUTICAL  PRACTICE 


<0 


^                         m    S                    !IL 

i            I 

484 


AERONAUTICAL  PRACTICE  43 

same  time  that  it  would  take  the  express  elevators  of  one  of  our  sky- 
scraping  towers  to  make  the  same  distance.  The  barograph  record 
of  Hoxsey's  flight  at  Belmont,  Park  October  27,  1910,  Fig.  32,  shows 
that  he  rose  to  a  height  of  over  5,000  feet  in  the  first  thirty  minutes. 
In  this  flight,  however,  he  found  the  wind  too  severe  and  reached 
an  elevation  of  only  6,500  feet;  in  attempting  to  get  down,  he  dropped 
the  whole  distance  in  less  than  fifteen  minutes,  having  been  blown 
backward  about  30  miles.  Fig.  33  shows  the  record  made  at  the 
same  time  and  place  by  Johnstone  when,  although  facing  the  wind, 
he  was  blown  backward  42  miles.  It  is  well  known  that  the  sudden 
transition  from  the  high  pressure  of  a  subaqueous  tunnel  or  founda- 
tion caisson  to  the  normal  sea-level  atmosphere  is  often  attended  with 
fatal  results,  and  it  does  not  seem  unlikely  that  the  reverse  process 
of  going  from  a  comparatively  low  pressure  to  a  much  higher  one  in  a 
short  time,  as  where  the  aviator  descends  from  a  height  of  9,000  to 
10,000  feet  in  less  than  10  minutes,  physical  inconvenience  might 
follow.  Experiments  carried  out  by  prominent  physicians  in  France 
show  that  such  an  experience  is  attended  by  a  considerable  increase 
in  the  blood  pressure  of  the  individual.  The  time  of  transition  is 
so  short  that  the  circulatory  system  does  not  have  time  to  adapt  itself 
to  the  change  in  pressure. 

The  aviator,  after  .a  quick  descent  from  anything  above  a  few 
thousand  feet,  suffers  from  headache,  ringing  in  the  ears,  and  a  high 
pulse,  and  his  feet  and  hands  are  apt  to  be  blue  and  numb — quite  as 
much  from  impeded  circulation  as  from  the  cold  experienced  at  a 
great  height.  These  experiments  invariably  showed  that  the  blood 
pressure  was  increased  as  much  as  30  to  40  per  cent,  despite  the  fact 
that  the  aviators  in  every  case  were  trained  athletes  in  full  form. 
The  rise  in  temperature  was  less  apparent  where  the  individual  was 
fatigued,  and  was  not  present  where  the  flight  did  not  exceed  a  height 
of  300  or  400  feet.  By  the  result  of  these  experiments,  the  importance 
of  descending  slowly  is  pointed  out,  as  well  as  the  dangerous  fatigue 
to  which  flight  at  high  altitudes  exposes  the  circulatory  apparatus 
by  provoking  increased  and  irregular  activity  of  the  heart.  That 
some  of  the  fatalities  ascribed  to  mechanical  defects  might  in  reality 
have  been  due  to  fatigue  of  the  human  machine,  seems  quite  possible. 

Methods  of  Altitude  Measurement.  Captive  Balloon.  Interest 
in  high  flying  and  altitude  records  is  so  general  that  a  description  of 


485 


486 


AERONAUTICAL  PRACTICE  45 

the  methods  employed  in  ascertaining  the  height  reached  by  an 
aviator  will  be  appropriate  here.  There  are  numerous  ways  of 
measuring  elevation — of  varying  degrees  of  accuracy — and  in  general 
the  simplest  and  easiest  are  the  least  accurate.  When  a  record  is  to 
be  made,  possibly  exceeding  a  rival's  by  a  few  feet  only,  exactness 
is  evidently  a  desideratum.  In  view  of  the  conditions,  however,  it 
is  naturally  out  of  the  question  to  reduce  matters  to  such  a  fine  point 
as  this.  A  rule  has  accordingly  been  adopted  recently  by  the  Aero 
Club  that  henceforth  an  altitude  flight  is  to  be  considered  as  making 
a  record  only  when  it  exceeds  by  at  least  300  feet  the  mark  previously 
set.  In  1908,  getting  up  as  much  as  300  feet  was  in  itself  considered 
a  record.  At  that  time  a  certain  amount  of  rope  with  a  captive 
balloon  attached  to  its  upper  end  sufficed  as  a  measure  of  the  height 
reached.  The  fact  that  a  calm  might  permit  the  balloon  to  rise 
straight  up  and  stay  there  or  a  wind  might  carry  it  along  some  dis- 
tance thus  reducing  its  vertical  height  above  the  ground  considerably 
made  little  difference.  As  a  matter  of  fact,  a  breeze  sufficient  to  do 
this  was  more  than  enough  to  prevent  a  flight  of  any  kind. 

Triangulation.  The  balloon  very  shortly  becoming  of  no  further 
use  as  an  altitude  indicator,  triangulation  was  resorted  to,  this 
method  being  employed  at  the  Harvard  Meet  near  Boston,  in  Sep- 
tember, 1910.  By  this  means,  two  observers  at  the  end  of  a  measured 
base  line  watch  the  soaring  machine  and  obtain  its  angle  of  elevation 
simultaneously.  From  these  two  angles  and  the  length  of  the  base 
the  other  two  sides  of  the  triangle,  and,  consequently,  the  height  of 
its  apex,  may  readily  be  calculated  with  the  aid  of  trigonometric 
formulas.  The  longer  the  base  line  adopted  and  the  more  accurate 
the  instruments  employed  for  the  observation,  the  more  exact  the 
result  will  be.  The  preparations  for  checking  the  heights  reached 
by  the  aviators  at  the  Harvard  Meet  were  the  most  elaborate  ever 
undertaken  in  this  country. 

It  was  assumed  that  a  height  of  10,000  feet  might  be  reached, 
which  required  that  the  points  of  the  base  line  be  located  something 
over  2  miles  distant  from  the  aviation  field,  in  order  to  obtain  angles 
which  could  be  conveniently  observed  with  an  ordinary  surveyor's 
transit.  The  time  of  the  observations — late  afternoon — necessitated 
a  position  south  of  the  field  in  order  that  the  observers  might  have 
the  sun  behind  them,  and  made  possible  the  utilization  of  high  ground 


487 


46  AERONAUTICAL   PRACTICE 

for  the  observation  stations.  The  work  was  carried  on  under  the 
supervision  of  Prof.  R.  W.  Wilson,  of  Harvard  University,  Albert 
J.  Holmes,  an  engineer  of  Cambridge,  being  stationed  at  the  other 
observation  point.  Station  A  was  located  on  the  slope  of  Forbes 
Hill,  Quincy,  and  Station  B  was  at  East  Milton  in  an  open  field. 
Either  station  could  be  seen  from  the  other,  but  as  a  direct  measure- 
ment could  not  conveniently  be  made  between  them,  the  distance 
was  figured  from  indirect  measurements  and  was  found  to  be  6,236 
feet.  The  distance  from  the  aviation  field  was  about  2f  miles,  so 
that  had  any  one  of  the  aviators  reached  an  altitude  of  10,000  feet, 
his  angle  of  elevation  would  not  have  exceeded  35  degrees. 

Back  of  each  station,  in  the  line  of  the  base,  range  poles  covered 
with  alternate  strips  of  black  and  white  cotton  cloth  and  surmounted 
by  a  signal  flag  were  erected.  Around  the  hub  marking  each  station, 
three  stakes,  on  which  to  place  the  instrument,  were  driven  flush  with 
the  ground,  thus  insuring  a  quick  and  stable  set-up.  Sun  and  wind 
shelters  for  the  instruments  were  also  provided,  and  telephone  con- 
nections were  made  between  the  two  stations  and  with  Professor 
Wilson's  office  on  the  aviation  field. 

The  recorder  at  each  station  was  also  the  telephone  operator, 
who  was  provided  with  a  head  and  breast  attachment  for  receiver 
and  transmitter.  When  notice  was  received  from  the  field  that  an 
altitude  flight  was  about  to  be- attempted,  both  stations  were  called 
and  the  standard  chronometer  time  given.  The  operators'  watches 
were  compared  with  this  standard  and  the  result  recorded.  At  the 
same  time,  the  name  of  the  aviator  and  the  type  of  machine  to  be 
used  were  given.  As  soon  as  the  aeroplane  could  be  seen  from  both 
stations,  the  recorder  at  Station  A  would  give  the  word  to  get  ready, 
at  which  both  the  observers  trained  their  instruments  on  the  aviator 
himself,  Fig.  34,  as  representing  the  center  of  gravity  of  the  machine. 
An  answer  of  "all  right" was  then  passed  back  to  Station  A.  - 

Each  observer  then  followed  the  movements  of  the  aeroplane 
by  turning  the  upper  motion  of  the  transit  with  his  left  hand — the 
lower  motion  having  been  set  at  zero  on  the  base  line — and  moving 
the  telescope  up  or  down  with  his  right  hand  by  means  of  the 
tangent  screw  on  the  vertical  circle.  The  signal  "all  right"  was 
repeated  back  and  forth  until  the  recorder  at  Station  A  would  say 
"set,"  at  which  the  observers  would  cease  moving  their  instruments 


488 


AERONAUTICAL  PRACTICE  47 

and  read  to  the  recorder  the  resulting  horizontal  and  vertical  angles. 
At  the  same  signal  each  recorder  noted  the  time  to  the  nearest  second. 
The  recorded  time  reduced  to  standard  time  served  to  identify  corre- 
sponding observations.  Eight  series  of  observations  were  taken  on 
five  different  days  during  the  course  of  the  meet.  While  there  was 
nothing  new  in  the  methods  thus  employed  in  determining  altitude, 


'Fig.  34.     Triangulation  Method  of  Measuring  Altitudes 

the  conditions  were  such  as  to  call  for  smoothly-working  instruments 
in  perfect  adjustment,  and  the  observers  and  recorders  had  neces- 
sarily to  be  on  the  alert.  Approximate  heights  obtained  by  sextant 
observation  were  announced  on  the  field  after  each  flight.  Aneroid 
barometers  and  other  apparatus  were  also  used  on  the  machines 
themselves,  but  the  official  altitudes  were  computed  from  the  obser- 


489 


4$  AERONAUTICAL   PRACTICE 

vations  described  above  and  were  made  public  only  after  having 
been  carefully  worked  out  at  the  close  of  the  day's  events.  The  best 
height  reached  during  the  course  of  this  meet  did  not  approach  the 
existing  record  at  that  time.  It  was  a  flight  of  3,860  feet  made  by 
Brookins  in  a  Wright  biplane.  The  same  aviator  had  previously 
ascended  over  5,000  feet  at  Atlantic  City,  his  altitude  being  deter- 
mined by  the  same  method  of  triangulation  here  described. 

The  cumbersomeness  of  the  elaborate  preparations  involved 
as  well  as  the  number  of  trained  observers  and  the  apparatus  required 
for  carrying  out  this  method  call  for  scarcely  any  comment.  Even 
were  it  a  method  that  could  be  universally  applicable,  or,  in  other 
words,  adapted  to  any  conditions,  it  could  hardly  come  into  general 
use,  although  the  fact  is  conceded  that  it  is  the  most  accurate  method. 
It  will  be  evident  that  as  it  depends  entirely  for  its  working  upon  the 
ability  of  the  observers  to  follow  the  aeroplane,  regardless  of  the 
height  it  attains,  the  habit  of  rising  "clear  out  of  sight"  that  has  been 
indulged  in  by  the  aviators  in  recent  record-breaking  flights  would 
put  the  entire  system  out  of  commission.  This  would  likewise  be  the 
case  where  there  were  any  low  clouds  or  mist  to  obscure  the  view. 

A  method  of  triangulation  can  also  be  employed  from  the  aero- 
plane itself,  but  has  the  disadvantage  of  requiring  an  observer  for 
this  purpose,  while  observations  would  be  difficult  at  the  high  rate 
of  speed  ordinarily  attained  by  the  heavier-than-air  machine.  The 
method  is  more  applicable  for  use  in  a  balloon  or  dirigible.  It  con- 
sists of  observing  two  points  of  the  imaginary  base  line  of  a  triangle 
on  the  ground  with  the  aid  of  an  instrument  having  a  graduated 
scale.  The  length  of  this  base  line,  or  distance  between  the  two 
points  on  the  ground  selected  by  the  observer,  is  evidently  in  inverse 
proportion  to  the  distance  from  the  observer's  location  in  the  balloon 
to  one  of  the  points.  The  observer  sights  an  object  of  known  dimen- 
sions, such  as  a  house  or  a  tree,  thus  measuring  the  apparent  angle 
under  which  it  is  seen. 

Acoustic  Method.  There  is  also  the  acoustic  method  by  which 
rough  approximations  can  be  obtained  of  moderate  heights.  It  con- 
sists in  measuring  the  time  necessary  for  sound  to  traverse  the  dis- 
tance which  separates  the  aviator  from  the  ground  and  is  likewise  only 
applicable  to  the  balloon  or  dirigible,  also  involving  a  special  observer 
to  carry  it  out.  Any  distinct  noise  made  by  the  aeronauts  will  be 


490 


AERONAUTICAL   PRACTICE  49 

deflected  or  echoed  by  the  surface  of  the  earth  and  returned  to  them 
after  a  certain  lapse  of  time,  measured  by  their  distance  in  the  air. 
By  accurately  noting  the  time  required  for  a  sharp  blast  on  a  horn 
to  reach  the  earth  and  return  as  an  echo,  and  multiplying  this  by  the 
speed  at  which  sound  travels,  the  result  obtained  will  be  twice  the 
distance  above  ground.  However,  since  the  speed  of  sound  is  340 
meters  per  second,  it  would  be  easy  to  make  such  serious  mistakes 
in  the  observations  as  to  render  the  latter  entirely  worthless  for  any 
practical  purpose,  a  difference  of  only  one-fifth  of  a  second  making 
a  variation  of  more  than  100  feet  in  height.  Even  though  obtained 
by  accurate  observations,  the  result  also  requires  changes  and  cor- 
rections according  to  the  density  of  the  atmosphere,  and  it  may  be 
altogether  erroneous  if  there  happen  to  exist  ascending  or  descending 
currents  of  air  at  that  point  at  the  time  the  observations  are  made. 

It  will  be  easy  to  appreciate,  for  instance,  how  difficult  it  would 
have  been  to  ascertain  the  heights  attained  in  any  of  the  attempts 
at  altitude  records  that  marked  the  close  of  1910.  The  rivalry  to  be 
the  first  to  attain  10,000  feet  was  very  keen.  Drexel  came  very  close 
to  this  mark,  his  corrected  readings  showing  a  shortage  of  only  a  little 
over  100  feet.  The  record  was  finally  made  by  Legagneux,  who, 
soaring  over  Pau,  France,  reached  a  height  of  10,499  feet.  Then 
Hoxsey,  in  a  Wright  biplane,  ascended  almost  1,000  feet  higher  at 
Los  Angeles  on  December  27,  1910.  This  represents  a  distance  of 
nearly  2  miles  from  the  earth  and  long  before  that  height  is  reached 
such  a  small  object  as  an  aeroplane  becomes  invisible  to  the  naked 
eye,  and  while  it  ^vould  be  extremely  difficult  for  one  observer  with 
a  telescope  to  keep  the  tiny  speck  in  view,  it  would  be  much  more 
difficult  for  two  to  follow  it  constantly. 

In  the  case  of  Hoxsey's  record-breaking  flight,  his  machine  was 
completely  lost  to  view  for  more  than  an  hour,  and  although  sub- 
sequent events  showed  that  he  had  gone  practically  straight  up  over 
the  aviation  field — coming  down  again  at  the  same  place — it  was 
impossible  for  numerous  experienced  observers  to  sight  him  even  with 
the  aid  of  strong  field  glasses.  In  fact,  as  the  ascent  was  made 
in  little  short  of  a  gale — the  wind  blowing  forty  miles  an  hour — it 
was  feared  that  he  had  been  blown  away  and  surrounding  towns 
were  notified  to  be  on  the  lookout  for  the  machine.  Only  a  few 
years  ago,  there  was  scarcely  an  aviator  who  dared  rise  in  the  air 


491 


50 


AERONAUTICAL  PRACTICE 


when  there  was  more  than  a  zephyr  stirring,  so  that  Hoxsey's  ascent 
was  an  extraordinary  feat  in  more  than  one  sense,  affording  a  striking 
illustration  of  the  stability  of  the  biplane.  The  same  wind  but  a 
short  time  before  had  brought  Latham's  huge  Antoinette  monoplane 
to  grief.  (It  was  Latham  who  set  the  initial  high  mark  for  1910  at 
3,445  feet,  in  France.)  On  landing,  Hoxsey  was  so  benumbed  that 
he  could  scarcely  speak  and  had  to  be  lifted  from  his  seat  and  sup- 
ported until  his  circulation  again  approached  the  normal. 


Fig.  35.     Barograph  Mounted  so  as  to  Prevent  Vibration 

Barograph.  The  aeroplane  accordingly  outgrew  the  triangula- 
tion  method  of  ascertaining  the  height  reached  after  it  had  been  given 
a  few  trials.  Although  its  accuracy  is  indisputable,  this  being  the 
means  employed  by  civil  engineers  to  determine  the  height  of 
mountains,  it  was  not  depended  upon  solely  even  on  the  occasions 
in  question,  a  barograph  being  placed  on  the  machine  in  addition. 
Now  that  invisible  heights  have  been  attained,  even  under  the  clearest 
weather  conditions,  the  barograph  is  the  only  resource. 


492 


AERONAUTICAL   PRACTICE 


51 


TABLE  I 
Fall  of  Barometer  at  Different  Elevations  above  Sea  Level 

(Latitude  40  degrees) 


Height  above  Sea  Level 
Feet 

Fall  of  Barometer 
Inches 

917 

1 

1,860 

2 

2,830 

3 

3,830 

4 

4,861 

5 

The  barograph,  as  its  name  indicates,  consists  of  a  recording 
aneroid  barometer  which  for  aeroplane  use  is  housed  in  a  light  but 
strong  glass  case,  as  shown  by  Fig.  35.  The  aneroid  barometer 
proper  is  a  very  delicately  made  and  adjusted  vacuum  box,  or  rather 
a  series  of  exhausted  cells  of  very  thin  metal,  placed  one  above  the 
other.  It  is  so  delicately  adjusted  that  it  is  susceptible  to  very  slight 
changes  in  atmospheric  pressure,  contracting  as  the  pressure  increases 
and  expanding  as  the  pressure  decreases,  as  in  ascending.  Its  move- 
ments are  transmitted  through  a  series  of  multiplying  levers  to  a 
pivoted  lever  carrying  at  its  end  a  small  pen  and  a  supply  of  ink. 
This  pen  bears  against  a  chart  wound  upon  a  hollow  drum,  the  latter 
being  revolved  by  clockwork.  The  chart  is  graduated  according  to 
the  metric  system,  usually  representing  meters  of  ascent,  the  divisions 
being  of  one  millimeter  each;  or  in  hundred ths  of  an  inch,  representing 
feet  of  ascent.  The  abscissas  of  the  chart  mark  the  ascent  or  descent 
and  the  ordinates  mark  divisions  of  time. 

A  mercury  barometer  falls  approximately  1  inch  for  every  900 
feet  of  ascent,  as  can  be  seen  from  Table  I  compiled  at  mean 
atmospheric  pressure  in  latitude  40  degrees. 

But  despite  its  sensitiveness  and  delicacy  of  adjustment,  the 
use  of  the  barograph  is  not  without  its  drawbacks.  It  is  affected 
adversely  by  the  vibration  of  the  motor  and  to  guard  against  this 
various  expedients  are  resorted  to.  In  one  of  his  attempts,  Latham 
suspended  the  instrument  around  his  neck — a  plan  that  rendered  it 
necessary  to  take  his  hands  from  the  control  in  order  to  consult  it, 
and  one  that  might  prove  annoying  in  other  ways.  Ordinarily,  it 
is  suspended  by  three  spring  straps  from  guy  wires  or  other  con- 


493 


52  AERONAUTICAL   PRACTICE 

venient  points  on  the  machine  where  it  will  be  in  plain  sight  of  the 
aeronaut,  Fig.  35.  As  far  back  as  twenty  years  ago  Colonel  Renard 
adopted  the  scheme  of  suspending  the  barometer  itself  inside  its  box 
or  housing  by  means  of  rubber  bands  fastened  to  the  different  cor- 
ners, thus  isolating  the  instrument  somewhat  after  the  manner  of 
a  spider  hanging  in  the  middle  of  its  web.  The  barometer  thus 
protected  was  employed  in  connection  with  sounding  balloons  and 
it  was  found  that  a  fall  of  12  to  15  feet  had  no  effect  on  it. 

A  further  disadvantage  of  the  barometer  is  what  may  be  termed 
its  lag,  or  retardation.  In  other  words,  it  does  not  respond  instantly 
to  the  change  of  pressure.  This  lag  will  be  more  or  less  accentuated 
according  to  the  rapidity  with  which  the  altitude  is  attained  and  the 
pressure  correspondingly  modified,  so  that  in  order  to  obtain  a  cor- 
rect reading  at  any  given  height  a  brief  period  must  be  allowed  to 
permit  the  instrument  to  accommodate  itself  to  the  changed  atmos- 
pheric conditions.  The  rapidity  with  which  it  will  do  this  depends 
in  large  measure  on  the  extent  of  the  difference  between  the  actual 
and  recorded  pressure  at  the  moment.  Where  the  variation  is  great 
the  force  tending  to  overcome  the  inertia  of  the  instrument  is  corre- 
spondingly increased,  and  the  atmospheric  pressure  may  be  said  to 
accumulate  a  head,  analogous  to  a  column  of  water,  this  being  true 
of  thermal  as  well  as  barometric  variation  in  its  influence  upon  the 
recording  instrument.  But  even  with  this  allowance  for  accommoda- 
tion to  changed  conditions,  the  barograph  indications  only  approach 
the  actual  height  in  a  varying  degree,  experience  having  demon- 
strated that  this  is  almost  always  more  or  less  inferior  to  the  real 
altitude  attained. 

Since  the  reading  of  the  instrument  denotes  only  the  difference 
in  pressure  between  the  point  of  departure  and  the  altitude  attained, 
the  barograph  employed  must  be  calibrated  just  before  being  used, 
and  its  record  is  also  subject  to  correction,  depending  upon  the 
atmospheric  conditions  prevailing  at  the  time.  In  fact,  a  resume 
of  the  precautions  observed  on  the  occasion  of  Drexel's  flight  at 
Philadelphia  would  make  it  appear  that  this  apparently  very  simple 
method  is  almost  as  elaborate  as  that  required  to  obtain  a  similar 
result  by  triangulation.  The  instrument  employed  was  a  Richard, 
of  French  make,  but  similar  in  construction  to  the  barograph  manu- 
factured by  Queen  and  Company,  Philadelphia,  and  illustrated  here. 


494 


AERONAUTICAL   PRACTICE 


53 


Being  compensated  for  temperature,  the  barograph  requires  no 
correction  for  the  effect  of  temperature  on  the  instrument  itself, 
but  its  reading  requires  correction  for  the  effect  of  temperature  on 
the  atmosphere,  which  need  be  taken  into  consideration  only  when 
the  latter  is  above  or  below  50°F.  That  this  may  be  the  case  fre- 
quently, in  fact  practically  always,  is  illustrated  by  the  sufferings  of 
aviators  at  high  altitudes.  In  the  monoplane  with  the  motor  at  the 
head,  the  aviator  sits  directly  in  the  blast  of  the  propeller  and  it 


Fig.  36.     Drexel  Preparing  for  an  Altitude  Flight 

appears  to  be  next  to  impossible  to  wear  sufficient  clothing  to  pre- 
vent suffering  from  the  cold.  Drexel,  Fig.  36,  wore  several  sweaters 
in  addition  to  a  specially  fleece-lined  skin  suit.  The  daily  press 
reports  of  Hoxsey's  flight  at  Los  Angeles  mentioned  that  the  aviator 
was  afraid  that  "the  carbureter  of  his  motor  would  freeze,"  in  other 
words,  choke  up  with  ice  and  stop  the  motor.  This  might  have  been 
the  case  with  a  motor  of  the  ordinary  type,  but  the  Wright  motor 
could  hardly  suffer  from  such  a  defect  as  it  is  not  equipped  with  a 


495 


54  AERONAUTICAL   PRACTICE 

carbureter  of  any  kind.  Instead,  it  is  fitted  with  a  small  gasoline 
pump  which  forces  the  fuel  directly  to  the  inlet  valve  of  each  cylinder. 
As  an  automatic  inlet  valve  is  employed,  the  spring  tension  of 
the  valves  might  prove  excessive  under  the  diminished  pressure 
encountered  at  high  altitudes,  thus  greatly  cutting  down  the  supply 
of  air  through  the  decrease  in  the  maximum  opening  of  the  valve,  but 
this  does  not  appear  to  have  occasioned  any  trouble  thus  far.  The 
Antoinette  motor  is  also  fitted  with  a  gasoline  pump  to  feed  the  fuel, 
instead  of  the  usual  carbureter.  In  the  case  of  the  latter,  the  lower- 
ing of  the  temperature  is  aggravated  by  the  rapid  evaporation  at  the 
air  intake,  a  tendency  that  has  brought  about  a  very  general  use  of 
the  water-jacketed  type  of  carbureter  on  the  automobile. 

In  reading  the  barograph,  it  is  customary  to  apply,  for  correction 
of  temperature,  the  carefully  worked  out  tables  of  Sir  G.  Airy,  late 
British  royal  astronomer.  Carrying  the  instrument  about  is  apt  to 
derange  it  through  the  jolting  it  receives,  so  that  in  order  to  insure 
accuracy,  it  is  necessary  to  calibrate  it  before  a  flight.  Before  Drexel's 
attempt  at  record  breaking,  his  Richard  barograph  was  carefully 
tested  by  the  experts  of  Queen  and  Company,  with  the  assist- 
ance of  the  expert  of  the  weather  bureau.  This  was  done  by 
placing  the  instrument  in  the  receiver  of  a  large  air  pump  and  exhaust- 
ing the  air.  Connected  with  the  partial  vacuum  in  which  the  instru- 
ment rested  was  a  column  of  mercury,  which  had  previously  been 
accurately  adjusted  for  temperature,  altitude,  and  capillarity.  In 
the  course  of  exhausting  the  air,  the  instrument  passed  through  all 
the  changes  represented  by  an  ascent  from  sea  level,  or  an  atmospheric 
pressure  of  29.92,  to  an  elevation  of  15,000  feet,  and  was  found  to 
register  in  absolute  coincidence  with  the  mercurial  column.  The 
inclosing  cover  having  a  glass  front  and  permitting  the  instrument 
to  be  seen,  but  not  touched,  was  then  sealed,  and  attached  to  the 
Bleriot  monoplane.  Immediately  after  the  conclusion  of  the  flight, 
the  instrument  was  again  taken  to  the  laboratory  and  subjected  to  a 
similar  test,  which  proved  it  to  be  in  good  order  and  correct  in  its 
indications.  The  following  are  the  results  of  the  examination: 

The  difference  in  atmospheric  pressure  between  the  upper  and 
lower  stations  on  the  barograph  record  was  9.302  inches.  At  the 
time  of  the  ascension  the  pressure  at  the  ground,  as  indicated  by 
the  record,  was  30.05  inches  and  at  the  altitude  attained  was  20.75 


49S 


AERONAUTICAL   PRACTICE  55 

inches,  giving  a  difference  of  9,929  feet  on  the  basis  of  pressure  at 
sea  level  of  29.90  inches  at  a  temperature  of  the  air  of  50°F.  Making 
a  correction  to  the  pressure  of  the  lower  station  (plus  136  feet),  cor- 
rection to  the  mean  temperature  of  the  air  column  (minus  205  feet), 
correction  for  the  gravity  at  Philadelphia  which  is  in  latitude  40 
degrees  North  (plus  5  feet) ,  correction  for  moisture  in  the  air  column 
(plus  32  feet),  we  have  9,929  plus  136  plus  32  plus  5  minus  205  feet= 
9,897  feet,  as  representing  the  actual  altitude  reached. 

The  temperature  of  the  upper  air  is  also  of  some  importance  in 
determining  the  final  result,  and  while  no  recording  thermometer 
was  carried  by  Drexel,  it  just  so  happened  that  the  United  States 
Weather  Bureau  had  its  temperature  kites  flying  from  Mt.  Weather 
at  an  altitude  of  13,000  feet,  the  air  currents  at  the  time  flowing  from 
the  southwest  directly  over  Philadelphia.  It  was  thus  possible  to 
apply  an  accurate  correction  for  the  temperature  of  the  upper  air 
stratum,  there  being  at  that  altitude  no  local  conditions  to  affect 
the  result. 

From  the  foregoing,  it  will  be  apparent  that  the  making  of  an 
altitude  record  with  the  barograph  is  almost  as  delicate  and  involved 
a  matter  as  determining  the  height  by  triangulation.  For  the  com- 
parison of  records  and  to  establish  indisputably  the  rights  of  each 
competitor,  it  is  essential  that  the  results  be  determined  with  the 
utmost  exactitude  attainable.  Thus  Drexel's  flight,  while  an 
extremely  creditable  performance,  particularly  in  view  of  the  time 
of  year  it  was  made,  did  not  constitute  a  breaking  of  the  record 
made  by  Johnstonel  in  the  special  Wright  biplane  at  Belmont  Park 
a  month  earlier,  as  his  increase  did  not  exceed  the  new  limit  of  100 
meters,  or  328  feet,  the  actual  difference  being  only  183  feet.  On 
the  other  hand,  the  public  is  anxious  to  know  results  on  the  spot, 
and  to  satisfy  the  clamor  the  actual  reading  of  the  barograph  is 
usually  given,  it  being  understood  that  such  figures  are  subject  to 
modification  by  careful  verification,  as  precision  is  incompatible 
with  rapidity. 

In  addition  to  the  numerous  corrections  that  have  to  be  made 
before  the  record  can  be  considered  properly  verified,  there  is 
also  the  danger  of  deranging  the  instrument  through  the  jolts  it 
may  receive  in  the  starting  and  alighting  of  the  aeroplane.  The 
barograph  must  be  calibrated  just  previous  to  the  ascent  and  veri- 


497 


56 


AERONAUTICAL   PRACTICE 


fied  as  soon  afterward  as  possible,  the  former  being  particularly 
necessary  as  the  instrument  may  have  been  carried  a  long  distance 
in  an  automobile  or  railway  train,  as  was  the  case  with  Drexel's 
instrument. 

Individual  Barograph  Records.  Johnstone.  A  comparison  of 
the  experiences  of  aviators  who  have  reached  great  heights  is  of 
interest  in  this  connection.  In  making  his  record-breaking  flight 
at  Belmont  Park,  the  barograph  record  of  which  is  shown  in  Fig. 
37,  Johnstone  was  only  35  minutes  in  reaching  the  8,000-foot  level, 
but  it  took  him  almost  an  hour  to  ascend  the  remaining  1,000  feet  of 
his  flight.  He  descended  at  a  terrific  rate  in  one  long  dive  that 


™*  /  /  /  rdr-TT  d:  :3io    I  T/r7  ,;  /  /  TT" 

I  /•  ^  L    «W  w  vf—rJ^-r-  rh->~  i~\—**   >»/  TT*  TT— fr-/%t  f~\  sf*  /-\  '*>Tjf"T^l        / I          I  1         I 


\ \ \    \    \    \    \    \    \    \    \ \ \ \ YI\ \ \ 


\V-\ \ \ \ \ \ \ \ \ \ \ \ V- 

\\\  \r\\\V\\\\\  V 


Fig.  37.     Barograph  Record  of  Johnstone,  Showing  Rapid  Ascent 

required  only  5  or  6  minutes  to  bring  him  back  to  the  ground — a 
somewhat  foolhardy  proceeding  that  might  have  had  serious  physical 
results,  as  already  explained  at  the  opening  of  the  present  subject. 
Johnstone  kept  his  motor  throttled  coming  down  and  accordingly 
did  not  have  the  terrifying  experience  that  Brookins  passed  through 
earlier  in  the  same  meet  when  he  was  forced  to  descend  from  a  height 
of  5,000  feet  in  the  Wright  "baby"  biplane  with  a  dead  motor.  The 
machine  was  considerably  damaged  in  alighting  but  Brookins  was 
unhurt. 

Johnstone  was  fond  of  "hair-raising  stunts"  such  as  these  steep 
dives  and  lost  his  life  shortly  after  as  the  result  of  a  similar  perform- 
ance at  Denver  in  the  middle  of  November.  On  the  occasion  of  his 


498 


AERONAUTICAL   PRACTICE 


57 


lofty  flight  at  Belmont  Park  in  October,  Johnstone  did  not  experience 
any  discomfort  from  his  exceedingly  rapid  transition  from  a  height 
of  almost  2  miles  with  its  rarefied  air  down  to  the  normal  atmospheric 
pressure  to  which  \ve  are  accustomed  at  sea  level. 

Drexel.  It  was  otherwise  with  Drexel  at  Philadelphia.  During 
his  first  attempt  to  break  Johnstone 's  record,  he  was  attacked  by 
mountain  sickness — one  of  the  numerous  fanciful  appellations  under 
which  nausea  travels — and,  in  addition,  he  was  numb  with  the  cold. 
At  the  time,  he  was  at  an  elevation  of  8,373  feet  which  he  had  attained 
in  about  45  minutes  and,  as  he  was  then  over  the  Atlantic  Ocean,  he 
immediately  started  downward  in  long  spiral  sweeps,  Fig.  38.  The 
second  attempt  was  made  a  few  days  later  and  it  accentuated  the 


*Y 

I 


n(W) 


I     I  I 


_ 

/  pcfr/j 


/ 


0f-f 


\  \  \  \  \ 


\    \    \    \    \  _l  -\    \    \    \    \ 


\  \  \  \  \ 


Fig.  38.      Barograph  Record  of  Drexel,  Showing  Rapid  Ascent  and  Descent 

experience  which  most  aeronauts  have  encountered  in  rising  to  a 
great  height — that  is,  the  ease  with  which  a  certain  altitude  between 
8,000  and  9,000  feet  is  attained  and  the  difficulty  met  in  getting 
any  higher — as  illustrated  by  the  fact  that  Johnstone  made  his  ascent 
of  the  first  8,000  feet  in  little  over  half  an  hour,  but  was  almost  an 
hour  in  rising  1,000  feet  more. 

When  Drexel' s  barograph  recorded  within  less  than  a  hundred 
feet  of  the  then  coveted  10,000-foot  mark,  it  seemed  impossible  to 
go  up  any  higher.  It  will  be  recalled  that  the  actual  reading  of  the 
instrument  lacked  only  71  feet  of  this  figure,  but  numerous  attempts 
to  ascend  farther  in  spirals,  as  is  usually  done,  made  no  impression 


499 


58 


AERONAUTICAL   PRACTICE 


TABLE  II 
Aeroplane  Altitude  Records  for  1910 


Date 

Name 

Machine 

Place 

~ 

Altitude 

Jan.     7 

Latham 

Antoinette  monoplane 

France 

3,280 

Jan.  12 

Paulhan 

Farman  biplane 

United  States 

4,165 

July    9 

Brookins 

Wright  biplane 

United  States 

6,171 

Aug.  11 

Drexel 

Bleriot  monoplane 

England 

6,600 

Sept.  3 

Morane 

Bleriot  monoplane 

France 

8,471 

Sept.  8 

Chavez 

Bleriot  monoplane 

France 

8,485 

Oct.     3 

Wynmalen 

Farman  biplane 

France 

9,104 

Oct.  31 

Johnstone 

Wright  biplane 

United  States 

9,714 

Nov.  23 

Drexel 

Bleriot  monoplane 

United  States 

9,897 

Dec.    9 

Legagneux 

Bleriot  monoplane 

France 

10,499 

Dec.  27 

Hoxsey 

Wright  biplane 

United  States 

11,474 

whatever  on  it.  The  expedient  of  making  a  sudden  dive  and  then 
shooting  upward  with  the  momentum  thus  gained,  roller-coaster 
fashion,  was  then  tried  but  failed  to  result  in  forcing  the  machine 
more  than  a  few  feet  higher.  The  descent  was  made  in  a  perfectly 
straight  line  at  an  angle  which  brought  the  machine  to  the  ground 
at  a  point  12  to  15  miles  distant  from  the  starting  field. 

Legagneux.  Although  Drexel  did  not  succeed  in  breaking  John- 
stone's  record  officially,  the  latter  only  remained  valid  for  a  very 
short  time,  Legagneux  reaching  a  height  of  3,200  meters,  or  10,499 
feet,  within  less  than  a  fortnight  later,  December  9,  1910.  This  was 
accomplished  in  a  Bleriot  monoplane  although  this  French  aviator 
had  previously  been  closely  identified  with  the  Farman  biplane.  In 
one  of  the  latter  machines  he  successfully  made  Le  Circuit  de  L'Est, 
one  of  the  leading  French  long-distance  flights,  constituting  prac- 
tically an  aerial  circumnavigation  of  France — a  trip  of  several  hun- 
dred miles.  He  also  made  the  180-mile  flight  from  Paris  to  Brussels 
with  a  passenger  in  a  Farman,  covering  the  distance  in  slightly  less 
than  3J  hours  or  an  average  for  the  distance  of  near  60  miles  an  hour, 
which  is  remarkable  in  view  of  the  load  carried. 

Summary  of  Altitude  Records.  How  rapidly  altitude  records 
followed  one  another  during  the  year  1910  will  be  evidenced  from  a 
glance  at  Table  II. 

As  the  new  rule  making  necessary  a  difference  of  100  meters  to 
constitute  an  official  record  went  into  effect  only  a  short  time  before 


500 


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Si 


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501 


60  AERONAUTICAL   PRACTICE 

Drexel's  flight  at  Philadelphia,  those  preceding  his  accomplishment 
were  officially  regarded  as  setting  up  new  altitude  marks  regardless 
of  the  slight  difference  that  may  have  actually  existed  between  the 
new  height  attained  as  compared  with  the  one  just  given.  This  is 
noticeable  in  the  flights  of  Morane  and  Chavez — the  latter  of  whom 
made  his  record  in  crossing  the  Italian  Alps — there  being  a  margin 
of  only  14  feet.  This,  taken  in  connection  with  the  numerous  cor- 
rections necessary  in  the  reading  of  the  barograph  before  the  actual 
height  attained  can  be  accurately  calculated,  makes  apparent  the 
wisdom  of  the  rule  in  question. 

That  the  instruments  will  give  remarkably  uniform  results 
when  carefully  checked,  however,  may  be  noted  from  the  experience 
of  the  International  Aviation  Meet  at  Belmont  Park,  in  October, 
1910 — one  of  the  most  important  events  of  the  year.  At  times, 
there  were  as  many  as  eight  or  ten  machines  of  different  types  in  the 
air  at  once.  All  of  the  altitude  instruments  used  were  'carefully 
calibrated  in  advance  by  Major  Samuel  Reber,  U.  S.  A.,  who  served 
as  a  member  of  the  Contest  Committee  of  the  Aero  Club  of  America. 
The  formula  of  Laplace  was  used  in  this  work  and,  as  the  corrections 
for  temperature  were  allowed,  the  results,  as  shown  by  the  barograph 
records  were  practically  correct.  Each  instrument  was  calibrated 
separately,  the  readings  being  checked  at  every  50  millimeters  on 
the  chart.  So  accurate  were  the  results  thus  obtained,  that  two 
barographs  sent  aloft  on  the  same  aeroplane  varied  from  each  other 
by  only  13  feet,  or  less  than  the  width  of  one  of  the  recording  lines 
which  were  equivalent  to  a  height  of  17  feet. 

In  view  of  what  has  been  accomplished  in  less  than  a  dozen 
attempts  spread  over  the  course  of  a  year,  it  would  be  futile  to  attempt 
to  predict  what  the  next  few  years  may  bring  forth  in  altitude 
records.  With  a  water- jacketed  carbureter  to  prevent  freezing  at 
the  low  temperatures  encountered  at  great  heights  even  in  mid- 
summer and  a  means  for  compensating  for  the  increasing  rarity  of 
the  air  in  order  to  prevent  the  efficiency  of  the  motor  from  falling 
off  too  rapidly,  as  the  supply  of  oxygen  decreases  in  proportion  to 
the  volume  of  air,  there  would  appear  to  be  only  one  limit  to  the 
heights  attainable — that  of  human  endurance.  Adapting  the  motor 
to  the  extreme  range  of  conditions  under  which  it  must  operate  in 
traveling  from  sea  level  to  an  altitude  of  2  to  3  miles  or  more  without 


502 


AERONAUTICAL  PRACTICE  61 

serious  loss  of  efficiency,  is  an  apparently  simple  matter.  In  addition 
to  the  precautions  against  freezing,  means  have  to  be  provided  for 
mixing  a  very  much  greater  volume  of  the  rarefied  air  with  the  gaso- 
line in  order  to  maintain  the  supply  of  oxygen  at  a  point  where  it 
will  be  sufficient  to  create  an  explosive  mixture  of  equal  power  to 
that  normally  obtainable  at  much  lower  levels.  Otherwise,  there 
would  appear  to  be  no  difficulty  in  running  the  motor  with  practically 
the  same  power  output,  regardless  of  the  height  attained.  Adding 
to  these  precautions  the  fact  that  at  certain  points  the  characteristic 
hourly  wind  velocities  for  different  altitudes  have  been  obtained, 
as  shown  in  Fig.  39 — a  sort  of  chart  of  the  air  which  will  warn  the 
aviator  of  the  dangers  he  is  liable  to  encounter — it  seems  as  if  all  of 
the  difficulties  except  those  inherent  in  the  aviator  himself  had  been 
guarded  against. 

The  ability  of  the  human  organism  to  withstand  the  sudden  tran- 
sition from  normal  atmospheric  pressures  to  a  very  low  pressure,  and 
vice  versa,  without  serious  physiological  results,  is  a  different  matter. 
There  are  undoubtedly  individuals  who  are  but  slightly  susceptible 
to  this  or,  at  any  rate,  very  much  less  so  than  others,  as  witnessed 
by  Johnstone's  experience,  and  with  inducements  in  the  form  of  cash 
prizes,  these  aviators  are  likely  to  come  forward.  At  present  the 
heights  attained  represent  only  about  a  third  of  the  distance  reached 
in  ordinary  spherical  balloons  and  slightly  more  than  this  propor- 
tion of  the  altitudes  reached  in  mountain  climbing,  Fig.  31.  It  is  true 
that  bleeding  at  the  nose  and  ears,  and  even  loss  of  consciousness, 
has  resulted  from  reaching  extreme  altitudes  in  a  comparatively 
short  time,  as  where  a  balloon  has  suddenly  shot  up  to  a  great  height. 
Being  overcome  in  this  manner  would  naturally  end  fatally  in  the 
case  of  the  aeronaut  who  has  to  be  alert  every  moment  in  order  to 
insure  his  safety.  He  has  no  sheltering  basket  in  which  he  can  safely 
remain  inert  until  the  recurrence  of  normal  conditions  revives  him. 
Despite  these  dangers,  it  seems  quite  probable  that  the  course 
of  the  next  few  years  will  mark  the  attainment  of  great  heights  in 
a  heavier-than-air  machine — in  fact,  altitudes  marking  the  limit 
beyond  which  human  life  can  not  be  sustained.  It  is  no  longer  a 
question  of  mechanics  nor  of  confidence  in  the  ability  of  the  machine 
to  accomplish  what  is  demanded  of  it,  but  merely  one  of  human 
endurance. 


503 


62  AERONAUTICAL   PRACTICE 

Although  the  air  has  the  apparent  advantage  of  being  a  high- 
way without  hills,  it  is  evident  that  there  is  more  need  for  climbing 
than  on  solid  ground,  and  this  need  will  increase  with  the  number  of 
aviators  until  it  will  become  necessary  to  go  up  or  down  to  avoid 
machines  approaching  from  other  directions.  Climbing,  in  fact,  is 
one  of  the  first  feats  to  be  mastered  for  at  the  very  start  the  aeroplane 
must  be  driven  upward  to  clear  obstructions.  If  the  angle  of  ascent 
be  too  great,  the  machine  may  very  quickly  lose  headway  and  come 
to  a  standstill,  under  which  circumstances  a  sudden  slant  in  almost 
any  direction  might  result  with  an  inexperienced  driver  and  would 
probably  be  followed  by  a  fall.  The  latter  would  be  caused  by  the 
almost  total  loss  of  the  effective  supporting  surface  through  such  a 
radical  alteration  of  the  angle  of  incidence. 

This,  and  the  experiences  of  Johnstone,  Drexel,  Hoxsey,  and 
others  who  have  ascended  to  great  heights,  suggest  the  importance 
of  employing  a  gradometer  on  the  machine.  When  these  aviators 
went  out  of  sight  of  the  ground,  and  particularly  when  enveloped  in 
a  cloud,  they  found  it  difficult  to  determine  whether  the  machine 
was  heading  up  or  down,  except  when  the  angle  was  acute  enough  to 
be  readily  perceptible.  The  gradometer  as  used  on  automobiles  is 
nothing  but  a  small  spirit  level  with  a  scale  calibrated  to  indicate 
the  angularity  of  ascent  or  descent  in  degrees.  Every  machine  has 
its  peculiarities  and  there  is  an  angle  at  which  it  climbs  most  effect- 
ively, while  in  the  case  of  fog  close  to  the  ground  it  would  be  of  great 
assistance  to  the  aviator  by  indicating  whether  the  aeroplane  was 
approaching  the  ground  or  the  reverse. 


504 


AERONAUTICAL  PRACTICE 

PART  II 


LEGAL  STATUS  OF  THE  ART 

Wright  Patents  in  American  and  Foreign  Courts.  Probably 
no  single  phase  of  aviation  is  as  little  known  by  those  who  should 
be  well  informed  on  the  subject  as  the  actual  status  of  aviation 
where  the  Wright  patent  is  concerned.  The  move  on  the  part  of  the 
Wright  Brothers  to  establish  the  standing  of  their  patents  by  hav- 
ing them  adjudicated  and,  as  this  is  an  extremely  lengthy  process, 
to  restrain  infringers  in  the  meantime,  has  led  to  a  perfect  flood  of 
criticism — even  abuse  and  vilification — all  of  which  has  been  mis- 
guided, to  say  the  least. 

A  clear  understanding  of  the  situation  as  it  now  stands  may  be 
obtained  from  the  following  brief  resume  of  the  events  that  led  up 
to  this  attitude,  nl  December,  1903,  the  Wright  Brothers  first  suc- 
ceeded in  flying  a  motor-driven  heavier-than-air  machine  guided 
by  man.  The  adoption  of  the  wing-warping  device  used  in  con- 
nection with  the  operation  of  the  vertical  or  direction  rudder  of  the 
machine,  which  made  this  possible,  marked  the  culmination  of  cen- 
turies of  effort  bent  upon  the  same  goal,  and  which  in  the  twenty 
years  just  preceding  had  engaged  the  talents  of  many  of  the  world's 
noted  scientists.  It  must  be  conceded  by  even  their  most  bitter 
antagonists  that  they  were  the  first  to  actually  fly;  moreover,  that 
although  others  may  have  suggested  or  even  attempted  to  use  a 
device  similar  to  theirs,  they  were  the  first  to  perfect  it,  and  that  the 
state  to  which  they  developed  it  made  the  general  introduction  of 
flying  possible.  To  refuse  to  admit  this  is  merely  going  contrary  to 
the  facts.  It  must  be  further  conceded  that  they  were  the  first  to 
obtain  patents  on  a  device  of  this  nature  which  had  actually  proved 
operative.  The  importance  of  this  will  be  pointed  out  later. 

There  is  accordingly  presented  on  the  one  hand  a  patentee  who, 
after  years  of  labor  and  the  expenditure  of  a  considerable  sum  of 

Copyright,  1912,  by  American  School  of  Correspondence. 


505 


64  AERONAUTICAL   PRACTICE 

money,  has  succeeded  in  inventing  a  device  of  an  absolutely  revolu- 
tionary nature;  on  the  other  hand,  an  enormous  number  of  inves- 
tigators in  the  same  field  who  wish  to  avail  themselves  of  his  hard- 
earned  success  without  in  any  way  contributing  to  the  reward  which 
should  be  his.  The  United  States  courts  held  that  Alexander  Graham 
Bell  was  the  first  to  perfect  a  device  for  the  transmission  of  speech 
over  a  wire.  A  situation  analogous  to  that  now  presented  in  the 
field  of  aviation  would  have  arisen,  had  the  public  claimed  the  right 
to  help  itself  to  Bell's  telephone  thirty  years  ago.  But  a  telephone 
could  not  be  manufactured,  bought,  or  sold,  for  love  or  money,  except 
by  the  Bell  Telephone  Company,  up  to  March,  1893— the  date  the 
patent  expired.  The  restriction  of  a  utility  of  such  far-reaching 
importance  could  be  criticized  as  an  unjust  monopoly,  and  undoubt- 
edly the  lack  of  competition  retarded  the  development  of  the  art,  as 
was  shown  by  the  strides  it  made  when  the  bars  were  let  down,  but 
there  was  no  possible  legal  basis  for  complaint. 

There  appears  to  be  little  doubt  but  that  the  Wright  patent 
is  quite  as  basic  as  that  of  the  telephone.  Speaking  over  a  wire  was 
generally  considered  quite  as  much  of  an  impossibility  before  Bell's 
invention,  as  flying  was  before  that  of  the  Wright  invention.  Whether 
the  Wright  Brothers  decide  to  grant  licenses  to  manufacture  on  a 
royalty  basis,  once  their  patent  has  been  successfully  adjudicated, 
is  entirely  for  them  to  decide.  Their  non-committal  attitude  on  the 
question  in  the  meantime,  despite  the  precedent  of  the  Selden  auto- 
mobile patent  under  which  numerous  licenses  to  manufacture  were 
granted  pending  its  ligitation,  has  led  to  a  great  deal  of  criticism 
with  "hampering  the  development  of  the  art"  as  its  chief  foundation. 
But  there  is  quite  another  side  to  the  question.  It  has  been  shown 
to  be  possible  to  fly  without  utilizing  the  Wright  device,  as  in  the 
original  Voisin  biplane,  but  not  with  any  great  degree  of  speed  or 
safety;  or  again,  as  in  the  case  of  the  Pfitzner  monoplane,  the  possibil- 
ities of  which  have  not  been  fully  put  to  the  test  as  yet.  The  necessity 
of  competing  against  the  patented  device  should  be  instrumental  in 
advancing  the  art,  instead  of  hampering  its  development.  It  is 
scarcely  necessary  to  add,  that  these  inventors,  unless  of  a  sufficiently 
philanthropic  turn  of  mind  to  dedicate  their  inventions  to  the  public, 
would  likewise  expect  to  reap  the  reward  of  their  efforts.  It  is  simply 
a  case  of  the  survival  of  the  fittest,  and  should  the  Wright  Brothers' 


506 


AERONAUTICAL   PRACTICE  65 

invention  prove  to  be  the  only  successful  method  of  flight,  as  it  has 
proved  thus  far — when  it  is  considered  that  all  successful  machines 
to  date  either  warp  the  planes  or  employ  a  method  which  is  claimed 
to  infringe  this — there  appears  to  be  no  reason  why  they  should  not 
legally  control  the  situation.  Their  attitude  toward  the  matter,  as 
noted  by  an  unbiased  observer  who  has  probably  had  a  better  oppor- 
tunity to  appreciate  the  status  of  affairs  as  they  really  exist,  leads  to 
the  belief  that  the  upholding  of  their  patent  rights  will  not  bring  into 
existence  any  restrictive  monopoly.  This  has  already  been  amply 
demonstrated  by  their  full  permission  for  the  employment  of  their 
device  in  experimental  work. 

What  they  have  attempted  to  stop  has  been  merely  the  manu- 
facture of  machines  alleged  to  infringe  their  patents  for  sale  and 
exhibition  purposes — in  other  words,  the  making  of  money  by  means 
claimed  to  have  been  made  possible  through  the  utilization  of  their 
ideas,  whether  in  the  same  or  a  modified  form.  In  brief,  the  legal 
steps  taken  thus  far  are  as  follows: 

The  patent  which  embodies  the  Wright  flying  machine  was 
issued  May  22,  1905.  In  the  latter  part  of  1909,  the  United  States 
Circuit  Court  was  appealed  to  to  enjoin  the  Herring-Curtiss  Com- 
pany and  Glenn  H.  Curtiss  from  manufacturing,  selling,  or  using  for 
exhibition  purposes,  the  Curtiss  aeroplane.  Contrary  to  established 
precedent  in  patent  litigation,  Judge  Hazel,  of  the  United  States 
Circuit  Court  in  Buffalo,  granted  a  preliminary  injunction  restrain- 
ing the  defendants  mentioned.  The  chief  question  at  issue  in  this 
instance  was  whether  or  not  movable  auxiliary  surfaces,  popularly 
termed  ailerons,  or  wing  tips,  constituted  an  infringement  of  the 
Wright  patent.  The  court  reviewed  the  Wright  patent  at  some  length, 
but  in  its  opinion  the  question  of  infringement  as  between  warping 
and  the  use  of  ailerons  is  the  only  one  of  importance  existing  at 
present.  On  this,  Judge  Hazel  said: 

Defendants  claim  generally  that  the  difference  in  construction  of  their 
apparatus  causes  the  equilibrium,  or  lateral  balance,  to  be  maintained  and  its 
aerial  movement  secured  upon  an  entirely  different  principle  from  that  of 
complainant;  that  defendants'  aeroplanes  are  curves  firmly  attached  to  the 
stanchions  and  hence  are  incapable  of  turning  or  twisting  in  any  direction; 
that  the  supplementary  planes  or  so-called  rudders  are  secured  to  the  forward 
stanchion  at  the  extreme  lateral  ends  of  the  planes  and  are  adjusted  midway 
between  the  upper  and  lower  planes  with  their  margins  extending  beyond  the 


507 


66  AERONAUTICAL   PRACTICE 

edges;  that  in  moving  the  supplementary  planes  equal  and  uniform  angles  of 
incidence  are  presented  as  distinguished  from  fluctuating  angles  of  incidence, 
which  claimed  functional  effects,  however,  are  strongly  contradicted  by  the 
expert  witness  for  complainant.  Upon  this  contention,  it  is  sufficient  to  say 
that  the  complainant's  affidavits  so  clearly  define  the  principle  of  operation 
of  the  flying  machine  in  question  that  I  am  reasonably  satisfied  there  is  a 
variableness  of  the  angle  of  incidence  in  the  machine  of  defendants  which  is 
produced  when  a  supplementary  plane  on  one  side  is  tilted  or  raised,  and  the 
other  simultaneously  tipped  or  lowered.  I  am  also  satisfied  that  the  rear 
rudder  is  turned  by  the  operator  to  the  side  having  the  least  angle  of  incidence 
and  that  such  turning  is  done  at  the  time  the  supplementary  planes  are  raised 
or  depressed  to  prevent  tilting  or  upsetting  the  machine. 

On  the  papers  presented,  I  incline  to  the  view,  as  already  indicated,  that 
the  claims  of  the  patent  in  suit  should  be  broadly  construed;  and  when  given 
such  construction,  the  elements  of  the  Wright  machine  ere  found  in  defend- 
ants' machine  performing  the  same  functional  result.  There  are  dissimi- 
larities in  the  defendants'  structure — changes  of  form  and  strengthening  of 
parts — which  may  be  improvements,  but  such  dissimilarities  seem  to  me  to 
have  no  bearing  upon  the  means  adopted  to  preserve  the  equilibrium,  which 
means  are  the  equivalent  of  the  claims  in  suit  and  attain  an  identical  result. 

Defendants  further  contend  that  the  curved  or  arched  surfaces  of  the 
Wright  aeroplanes  in  commercial  use  are  departures  from  the  patent  which 
describes  "substantially  flat  surfaces,"  and  that  such  a  construction  would  be 
wholly  impracticable.  The  drawing  attached  to  the  specification,  however, 
shows  a  curved  line  inward  of  the  aeroplane  with  straight  lateral  edges,  and 
considering  such  drawing  with  the  terminology  of  the  specification,  the  slight 
arching  of  the  surface  is  not  thought  a  material  departure.  At  any  rate,  the 
patent  in  issue  does  not  belong  to  the  class  of  patents  which  requires  narrow- 
ing to  the  details  of  construction. 

The  preliminary  injunction  restraining  Curtiss  was  accordingly 
granted  January  3,  1910.  About  the  same  time  the  United  States 
Circuit  Court  for  the  Southern  District  of  New  York  was  appealed 
to  to  restrain  Louis  Paulhan,  the  French  aviator,  from  using  a 
machine,  claimed  to  infringe  the  Wright  patents,  for  exhibition  pur- 
poses in  this  country.  Paulhan  contended  that  it  would  be  suicidal 
to  interconnect  the  operating  control  of  the  ailerons  and  the  direc- 
tion rudder;  that  either  may  be  and  is  used  independently  of  the 
other;  that  the  use  of  the  rudder  alone  will  prevent  "skidding"  and 
restore  the  aeroplane's  equilibrium;  and  that  complete  turns  may 
be  made  without  employing  the  ailerons  or  warping  the  wings.  An 
excerpt  from  Paulhan's  statement  on  this  point  is  as  follows: 

In  turning  a  corner  in  the  Farman  biplane,  or  any  aeroplane  with  which 
I  am  familiar,  it  is  not  at  all  essential  to  use  the  aileron  to  increase  the  angle 
of  incidence  on  the  outer  edge.  There  are  circumstances  in  making  a  turn  in 


508 


AERONAUTICAL   PRACTICE  67 

such  machines  and  in  straightaway  flight  when  the  operator  would  use  the 
aileron  or  warp  the  wings  without  turning  the  rudder  at  all,  and  very  often 
the  rear  vertical  rudders  are  used  without  any  interference  with  the  ailerons.* 
If  for  some  reason  such  aeroplanes  move  obliquely  to  their  longitudinal 
axis,  i.e.,  "skid,"  the  use  of  the  rudder  alone  will  correct  the  aeroplane's  equi- 
librium and  bring  it  back  to  its  normal  line  of  advance.  The  operator  can 
make  a  complete  turn  by  the  use  of  the  rear  vertical  rudders  alone  and  with- 
out using  either  ailerons  or  warping  to  correct  horizontal  equilibrium.  The 
rear  vertical  rudders  have  a  most  powerful  turning  effect  in  all  cases.  In 
making  a  sharp  turn  the  outer  end  of  the  aeroplane  may  be  tilted  up  and  a 
new  plane  of  movement  established  which  may  be  at  an  angle  of  ten  or  more 
degrees.  The  tendency  of  the  rudder  during  such  movement  is  to  swing  the 
tail  to  the  outer  side  of  the  turning  arc  with  great  rapidity.  Where  one  side  of 
the  Farman  biplane  is  depressed  or  tilted  downward,  that  side  tends  to  move 
more  slowly  and  the  aeroplane  turns  in  the  direction  of  the  depressed  side. 

These  statements  represent  a  condition  so  utterly  contrary  to 
what  the  Wright  Brothers  had  experienced  in  all  their  experiments 
as  absolutely  essential  to  flight,  that  they  invited  Paulhan  to  sub- 
stantiate his  theories  in  flight  in  their  presence,  making  his  ailerons 
fast  so  that  they  could  not  be  moved.  It  is  believed  that  some  of 
these  test  flights  were  actually  carried  out,  but  what  their  result 
was  does  not  appear.  At  any  rate,  Judge  Hand  granted  a  pre- 
liminary injunction  to  the  Wright  Brothers  against  Paulhan  on 
February  17,  1910,  requiring  the  defendant  to  file  a  bond  for  $25,000 
for  one  month's  flights.  This  was  shortly  afterward  changed  to 
$6,000  a  week. 

The  most  significant  part  of  Judge  Hand's  opinion,  which 
was  lengthy,  throws  considerable  light  on  what  he  considered  the 
invention  to  consist  of,  and  also  illustrates  what  is  regarded  as  the 
status  of  the  numerous  prior  patents  which  are  claimed  to  antici- 
pate the  Wrights'.  After  referring  to  the  Ader  machine  in  which 
there  was  a  provision  for  warping  the  planes,  he  says: 

The  mere  coincidence  of  these  parts  by  chance  or  as  a  matter  of  taste 
was  in  no  sense  an  anticipation  of  their  functional  correlation,  in  understand- 
ing which  the  complainant's  discovery  consists  and  with  it  their  invention. 

In  fact,  the  Wright  Brothers  state  in  their  application: 

We  are  aware  that,  prior  to  our  invention,  flying  machines  were  con- 
structed having  superposed  wings  in  combination  with  horizontal  and  ver- 
tical rudders. 


*Provision  is  made  in  the  Wright  machine  for  independent    use  of   either  warping  or 
vertical  rudder,  as  the  controlling  lever  may  be  moved  in  one  or  both  directions  at  will. — ED. 


509 


68  AERONAUTICAL   PRACTICE 

Some  of  the  more  important  patents  upon  which  the  claim  of 
anticipation  is  based  are  the  Mattullath  patent,  application  filed 
January  8,  1900;  the  Boswell  patent  dated  September  24,  1901; 
and  the  machines  of  Mouillard,  Le  Bris,  and  Ader,  discussed  in 
Chanute's  "Progress  of  Flying  Machines." 

At  a  time  when  the  controversy  is  at  its  height,  it  is  naturally 
difficult  to  reconcile  the  innumerable  conflicting  statements  and  the 
maze  of  contradictions  that  exist.  Where  what  is  known  as  the 
"prior  art"  is  concerned,  however,  it  would  appear  quite  probable 
from  a  statement  occurring  in  an  opinion  handed  down  by  the 
United  States  Circuit  Court  of  Appeals  in  New  York,  that  earlier 
patents  will  be  disregarded  where  they  have  not  been  shown  to  be 
operative,  which  would  naturally  exclude  practically  every  patent 
granted  prior  to  May  22,  1906.  The  action  in  question  was  in  regard 
to  a  railway  signal,  the  reference  in  the  opinion  being  by  way  of 
illustration  of  the  principle  that  a  patent  for  a  useful  device  will 
not  be  held  void  because  of  an  earlier  patent  for  a  useless  device. 

Success  can  not  be  anticipated  by  failure.  When  the  problem  of  aerial 
navigation  is  finally  solved  by  the  construction  of  a  secure,  dirigible  airship, 
it  is  safe  to  predict  that  the  inventor's  patent  will  not  be  invalidated  by  a  prior 
structure,  no  matter  how  perfect  it  may  be,  which  was  never  known  to  fly. 

As  already  mentioned,  it  was  quite  contrary  to  precedent  to 
grant  a  preliminary  injunction  restraining  an  alleged  infringer  before 
the  patent  was  actually  adjudicated,  i.e.,  upheld  in  an  action  to 
test  its  validity,  so  that  in  vacating  the  injunctions  against  Curtiss 
and  Paulhan  about  six  months  later,  the  Circuit  Court  of  Appeals 
simply  followed  the  long-established  precedent  of  American'  patent 
law.  As  a  general  rule,  preliminary  injunctions  are  not  countenanced 
in  patent  cases,  even  by  the  lower  courts.  It  seems  evident  upon 
reading  in  full  the  opinions  of  the  lower  courts  in  this  case,  and 
particularly  that  of  Judge  Hazel,  that  the  court  was  led  to  disre- 
gard precedent  through  what  appeared  to  be  the  clearness  of  the 
case  of  infringement  of  a  basic  patent  of  far-reaching  importance. 

The  reason  why  preliminary  injunctions  are  so  rarely  issued 
is  because  seldom,  indeed,  is  infringement  so  clearly  established 
that  a  court  is  justified  in  restraining  the  use  and  manufacture  of 
an  invention  before  the  question  of  patent  validity  is  decided.  The 
hardship  which  results  from  too  great  a  readiness  on  the  part  of  a 


510 


AERONAUTICAL   PRACTICE  69 

lower  court  to  restrain  an  alleged  infringer  is  strikingly  illustrated 
by  the  injunctions  issued  against  Curtiss  and  Paulhan.  As  a  result, 
the  Wright  Brothers  controlled  aviation  in  this  country  (L  e.,  exhibi- 
tion flights,  manufacture,  and  sale  of  machines)  absolutely  for  half 
a  year.  Unless  he  filed  a  bond  with  the  court,  no  aviator,  using  a 
machine  equipped  with  ailerons  or  wing-warping  devices  operated 
in  conjunction  with  a  vertical  rudder,  could  make,  sell,  or  fly  his 
apparatus  in  the  United  States. 

But  that  there  appeared  to  be  excellent  reason  for  departing 
from  established  precedent  in  this  instance  must  be  plain  to  anyone 
who  has  had  an  opportunity  to  review  the  correspondence  that 
passed  between  Curtiss  and  the  Wright  Brothers  prior  to  the  time 
that  Curtiss  began  to  build  or  exhibit  machines  for  profit.  Curtiss 
was  assisted  to  a  considerable  extent  in  the  design  and  construction 
of  his  machine  by  the  Wrights,  and  acknowledges  his  indebtedness 
to  them  for  information  of  this  nature  as  well  as  for  valuable 
data.  When  it  was  rumored  that  Curtiss  was  about  to  enter  the 
commercial  field,  the  Wright  Brothers  voluntarily  offered  to  take  up 
the  question  of  a  license  to  use  their  machines,  but  Curtiss  replied 
under  date  of  July  24,  1908,  that,  contrary  to  newspaper  reports,  he 
did  not  expect  to  do  anything  in  the  way  of  exhibitions.  This  cor- 
respondence was  all  placed  in  evidence  in  support  of  the  petition  for 
the  injunction,  and  it  was  further  shown  that  Bleriot  did  not  apply 
anything  in  the  nature  of  the  present  method  of  control  until  subse- 
quent to  the  publication  of  the  French  Wright  patent  in  1904.  In 
fact,  Captain  Ferber,  who  is  regarded  as  the  leading  French  authority 
on  aviation,  states  in  his  works  that  the  art  was  only  taken  up  in 
France  as  the  result  of  the  publication  of  the  Wright  Brothers'  early 
experiments  in  Europe.  There  has  seldom  been  a  case  in  patent 
litigation  where  infringement  of  a  sound  basic  patent  was  apparently 
so  clearly  made  out,  so  that  it  was  difficult  to  see  how  the  court  could 
refuse  to  grant  the  injunction  under  the  circumstances. 

The  vacating  of  these  injunctions  accordingly  forms  no  criterion 
of  the  final  outcome,  as  no  trial  on  its  merits  has  yet  been  held. 
The  Circuit  Court  of  Appeals  merely  held  that  infringement  was 
not  so  clearly  established  as  to  justify  a  preliminary  injunction.  A 
trial  of  the  action  against  the  Herring-Curtiss  Company  for  infringe- 
ment was  therefore  begun,  and  other  similar  actions  have  since 


511 


70  AERONAUTICAL  PRACTICE 

been  instituted,  notably  that  against  Claude  Grahame  White,  the 
English  aviator.  When  this  action  comes  to  trial,  Henri  Farman 
promises  to  produce  several  heretofore  unknown  foreign  patents 
which  he  has  acquired  and  which  are  claimed  to  clearly  anticipate 
the  Wrights'.  Meanwhile  the  Farman  Brothers  are  threatening 
to  prosecute  all  infringers  of  the  several  patents  they  hold  in  com- 
mon. In  view  of  the  opinion  of  the  Circuit  Court  of  Appeals  cited 
above,  Farman's  patents  would  not  appear  to  be  of  any  great  value 
as  evidence  in  this  country,  as  they  naturally  do  not  cover  a  machine 
that  actually  flew  before  that  of  the  Wright  Brothers.  The  Ger- 
man Wright  patent  has  recently  been  upheld  in  part,  although  the 
basic  feature  in  regard  to  the  simultaneous  action  of  the  rudder  and 
wing  flexing  has  been  invalidated. 

Under  the  laws  of  Germany  and  France,  a  disclosure  of  an  inven- 
tion by  the  inventors,  or  by  anyone  else  who  has  knowledge  of  it, 
before  the  application  for  a  patent  is  filed,  is  sufficient  to  render  the 
patent  void.  Such  disclosure  must  be  sufficient  to  enable  anyone 
to  understand  how  to  build  and  use  the  invention.  The  revelation 
of  the  invention  upon  which  the  German  patent  office  based  this 
decision  were  citations  from  L* Aeronaut,  Paris,  April,  1903,  giving 
a  report  of  the  address  of  Chanute  describing  the  Wright  experiments 
at  Kitty  Hawk  in  1902,  and  from  Automotor,  London,  February  15, 
1902,  giving  a  synopsis  of  the  address  of  Wilbur  Wright  before  the 
Western  Society  of  Engineers  in  1901,  describing  their  experiments 
of  that  year.  The  statement  of  Chanute  which  is  cited  as  a  disclo- 
sure of  the  Wright  invention  was  as  follows: 

"To  assure  transverse  equilibrium,  the  operator  works  two 
cords,  which  warp  the  right  and  left  wings  and  at  the  same  time 
adjust  the  vertical  rear  rudder." 

The  German  Patent  Office  has  taken  the  extreme  position  that 
these  few  words  were  sufficient  to  teach  anyone  how  to  build  and 
operate  a  flying  machine  in  1903,  and  that  they  canceled  the  right 
of  the  inventors  to  any  property  in  their  invention  in  Germany.  The 
Wright  Brothers  do  not  believe  that  this  decision  is  based  upon  a 
proper  interpretation  of  the  law  and  have  appealed  to  a  higher  tri- 
bunal, as  noted.  From  the  report  of  the  French  decision  given  fur- 
ther along,  it  will  be  apparent  that  the  French  court  took  a  far  more 
liberal  view  of  this  aspect  of  the  case.  The  court  upheld  two  specific 


512 


AERONAUTICAL  PRACTICE  71 

forms  of  patent,  combining  the  steering  and  flexing.  In  Germany, 
patent  procedure  is  the  reverse  of  what  it  is  here — a  patent  is 
presumed  to  be  valid  from  its  date  of  issue  until  proved  to  the 
contrary.  Accordingly,  five  German  firms  formed  a  syndicate  and 
brought  suit  to  have  the  Wright  patent  declared  of  no  value,  with 
the  result  mentioned.  This  decision  is  by  the  Patent  Office  and 
judgment  is  open  to  appeal  before  the  Imperial  Supreme  Court  at 
Leipzig,  action  to  this  effect  having  been  taken. 

In  France,  Le  Compagnie  Generale  de  Navigation  Aerienne,  the 
sole  French  concessionaires  of  the  Wright  patents,  brought  actions 
against  more  than  half  a  dozen  prominent  manufacturers  and  inven- 
tors, such  as  Bleriot,  Farman,  Antoinette,  Clement-Bayard,  Esnault- 
Pelterie,  Santos-Dumont,  and  others.  Santos-Dumont  alone  withdrew 
all  defense,  and,  curiously  enough,  he  is  the  only  defendant  in  whose 
favor  judgment  was  rendered,  on  the  ground  that  his  was  the  only 
aeroplane  that  was  not  built  for  purposes  of  trade  or  private  gain. 

The  types  of  aeroplanes  involved  were  the  Antoinette  and 
Bleriot  monoplanes  with  warping  wings,  the  Farman  with  ailerons  or 
"flaps"  at  the  rear  lateral  margins  of  the  planes,  and  the  Hautier- 
Vendome  with  ailerons  at  the  front  edges  of  the  wings.  A  large  part 
of  the  decision  relates  to  matters  of  French  law  which  renders  patents 
invalid  under  certain  conditions,  such  as  failure  to  work  an  invention 
within  three  years  of  the  time  of  applying  for  a  patent,  and  the  reve- 
lation of  an  invention  before  patenting  it.  The  decision  was  in  favor 
of  the  plaintiffs  in  all  of  the  cases  except  that  of  Santos-Dumont,  as 
mentioned,  but  before  rendering  final  judgment,  the  court  gave  the 
defendants  a  final  loophole  through  which  to  crawl,  if  possible,  by 
appointing  a  committee  consisting  of  M.  Leaute,  Major  Paul  Renard, 
and  Marcel  Deprez,  to  determine  whether  the  Wright  patent  of 
March  22,  1904,  had  not  been  anticipated  by  some  machine  unknown 
to  the  defendants  at  the  time  of  the  trial.  The  court  said  in  part: 

If  the  action  in  pursuit  of  a  claim  is  established  in  principle,  it  is  subor- 
dinated to  the  double  question  of  knowing  if  there  has  not  been  one  or  more 
priorities  of  all  the  parts  opposed  to  the  patent  of  1904,  and  if,  on  the  other 
hand,  it  will  not  be  found  void  as  against  certain  of  the  defendants,  as  they 
may  have  made  an  entirely  new  adaptation  of  the  mechanical  means  pointed 
out  by  the  Wrights  for  the  re-establishment  of  the  lateral  equilibrium,  and  of 
which  they  shall  have  conceived  a  structural  means  constituting  in  connection 
with  the  patented  invention  an  invention  entirely  new  and  original. 


513 


72  AERONAUTICAL  PRACTICE 

But  on  this  point,  a  writer  in  the  official  organ  of  the  Aero  Club 
of  France,  which  completely  controls  aviation  in  that  country,  says: 

The  mission  given  to  the  experts  is  singularly  limited,  and  does  not  allow 
the  defendants  any  hope  of  emerging  victorious  from  the  contest.  So  one 
should  not  be  astonished  that  many  of  the  defendants  already  express  an 
intention  of  appealing  from  a  judgment  which  they  consider  so  disastrous  to 
them. 

In  the  trial  of  the  action  the  plaintiffs  alleged  that  the  Wright 
patent,  being  their  personal  property,  gives  them  the  right  to  claim 
not  only  the  joint  and  separate  action  of  the  mechanism  of  the  rear 
direction  rudder  and  the  variation  of  the  angles  of  incidence  (to  wit, 
the  combination),  but  separately,  each  of  the  elements  of  this  com- 
bination in  so  far  as  it  is  employed  for  the  result  provided  for,  that 
is,  for  the  re-establishment  of  the  lateral  equilibrium  and  the  main- 
tenance of  the  direction  of  flight.  Wilbur  Wright  was  present  and 
testified  in  person. 

The  main  points  of  defense  presented  were:  That  the  Wright 
patent  was  not  valid  because  (1)  the  Wrights  had  revealed  their 
invention  before  applying  for  a  patent ;  (2)  they  had  not  worked  the 
invention  within  three  years;  (3)  the  invention  was  known  to  the 
prior  art.  Further,  that  the  defendants  did  not  infringe  the  patent, 
which  gives  the  plaintiffs  only  the  property  of  the  combination 
employed,  and  not  the  distinct  elements  which  are  employed  sepa- 
rately and  independently  for  the  same  purpose,  elements  which  they 
claim  are  public  property. 

The  claims  of  forfeiture  were  rejected  by  the  court,  the  substance 
of  the  decision,  stripped  of  its  Gallic  verbiage,  being  as  follows: 

(1)  That  the  subject  of  the  Wright  patent  of  March  22,  1904, 
was  patentable. 

(2)  That  it  was  impossible  to  keep  an  invention  of  this  nature 
entirely  secret,  and  the  photographs  and  descriptions  published  were 
not  sufficient  to  invalidate  it. 

(3)  That  the  Wrights  were  the  first  to  fly,  some  of  the  defend- 
ants having  claimed  that  flights  had  been  made  in  France  in  1898, 
and  that  they  had  invented  the  system  of  control  that  makes  flight 
possible. 

(4)  That  the  patent  had  been  worked  in  France  as  soon  as 
possible  under  the  circumstances. 

(5)  That  the  patent  was  valid. 


514 


AERONAUTICAL   PRACTICE  73 

(6)  That  the  independent  operation  of  the  wings  and  rudder  as 
used  by  the  French  was  not  sufficiently  claimed  in  the  Wright  patent, 
and  that,  therefore,  the  French  machines  were  not  infringements  of 
the  latter.  (This  is  apparently  a  "joker"  that  entirely  offsets  any 
value  the  decision  might  otherwise  have,  but  this  part  of  the  decision 
is  that  of  a  "substitute  judge,"  a  technical  expert  whose  services  are 
required  by  the  French  law  to  advise  the  courton  technical  mat- 
ters, and  it  was  subsequently  overruled  by  the  court  itself.) 

The  court,  composed  of  three  judges,  confirmed  the  above  find- 
ings with  the  exception  of  No.  6,  on  which  point  it  stated  that: 

While  the  independent  operation  of  the  wings  and  rudder  was  not  specif- 
ically claimed  in  the  words  of  the  patent,  yet  the  independent  operation  of  the 
parts  could  not  be  considered  as  a  new  invention,  but  simply  as  an  improve- 
ment in  detail  of  the  original  invention,  and  that  the  patentees  of  the  original 
invention  were  entitled  to  the  benefits  to  be  derived  from  it. 

By  referring  to  the  descriptions  of  standard  machines  it  will  be 
noted  that  none  of  the  French  defendants  were  makers  of  a  type  in 
which  the  ailerons  or  controllable  stabilizing  devices  were  entirely 
separated  from  the  main  supporting  planes,  as  is  the  case  in  the 
Curtiss,  in  which  the  ailerons  are  placed  between  the  main  surfaces 
of  the  biplane.  All  the  French  makers  built  infringing  types  of  mono- 
planes, with  the  exception  of  Farman.  This  is  practically  the  sole 
point  upon  which  the  entire  Wright  vs.  Curtiss  action  hinges,  and  in 
view  of  the  fact  that  it  seems  probable  the  United  States  Court 
will  extend  the  construction  of  the  patent  to  cover  the  use  of  sepa- 
rate ailerons  as  being  an  application  of  the  same  principle,  the  follow- 
ing resume  of  the  opinion  of  the  French  court  is  both  valuable  and 
instructive : 

Considering  the  point  once  established  that  the  separation  of  the  two 
elements  claimed  is  a  type  of  improvement,  this  separation  ought  to  be  con- 
sidered as  an  appurtenance  of  the  patent  of  1904,  that  the  improvement  is  a 
natural  development  of  the  primitive  invention  from  which  it  can  not  be  sepa- 
rated, and  that  proceeding  from  the  master  idea  which  is  the  generator  of  it, 
the  patentees  should  have  the  right  to  profit  by  it.  Of  what  little  importance, 
then,  is  it,  that  in  1907  the  Wright  Brothers  took  out  two  other  patents  in 
which  the  independence  of  the  warping  and  of  the  directing  rudder  was  expressly 
provided,  except  that  the  combination  of  the  two  elements  could  be,  if  desired, 
effected  by  the  hand;  admitting  that  these  two  patents  of  1907  repeat  in  cer- 
tain parts  the  things  which  can  be  found  in  the  patent  of  1904  and  that  even 
these  improvements  in  detail  which  were  then  meant  to  be  patented  were  with- 
out importance,  they  would  not  have  in  them,  to  say  the  least,  any  utility  as 
patents  of  extension. 


515 


74  AERONAUTICAL   PRACTICE 

It  will  be  noted  that  the  Court  reversed  the  opinion  of  the 
"substitute"  on  the  only  point  which  he  found  in  favor  of  the 
defendants.  In  reversing  this  point,  that  the  independent  operation 
of  the  wings  and  rudder  circumvented  the  patent,  the  Court  said: 

In  the  patent  of  1904  the  connection  of  the  warping  device  with  the  rudder 
is  so  minutely  described  that  it  can  be  understood  and  applied  by  engineers 
and  constructors  of  aeroplanes;  there  is  no  reason  to  believe  that  the  Wright 
Brothers  should  have  made  a  more  general  claim  and  should  have  claimed  each 
of  the  elements,  taken  separately,  but  they  should  be  confined  to  the  limits 
which  they  have  described  in  the  patent. 

After  the  patent  of  1904  the  invention  consisted  in  a  method  of  main- 
taining or  re-establishing  the  equilibrium  of  the  aeronautic  apparatus  and  of 
guiding  the  machine  in  a  vertical  or  horizontal  direction.  Among  other  ele- 
ments the  patent  provides  (1)  the  existence  of  two  horizontal  surfaces  or  wings, 
consisting  of  a  frame  on  which  fabric  is  spread,  and  connected  one  to  the  other 
by  means  of  posts  and  articulations,  which  permit  of  movements  of  torsion 
and  flection  of  the  ends  of  the  wings  in  opposite  directions;  (2)  of  a  vertical 
rear  rudder,  connected  to  the  cables  that  produce  the  torsion  of  the  ends  of 
the  wings. 

The  combination  of  the  two  elements  is  well  within  the  scope  of  the 
patent.  It  says  in  lines  14  to  19,  page  3: 

By  this  means  of  attachment  the  same  movement  of  the  cables  which  actuates 
the  ends  of  the  wings,  also  presents  to  the  wind  that  side  of  the  vertical  rudder  which 
is  turned  toward  the  end  having  the  smaller  angle  of  incidence. 

In  vain  the  suing  company  cites  two  other  passages  of  the  description. 
The  passage  from  the  34th  line  to  the  43rd  line  of  the  third  page  does  not  say 
that  the  rudder  can  be  independent;  nor  is  the  passage  from  the  45th  line  to 
the  57th  line  more  explicit: 

This  invention  is  not  limited  to  the  construction  and  attachment  of  the  rear 
rudder  herein  described,  nor  to  this  particular  construction  of  surfaces  or  wings, 
for  one  can  employ  this  combination  in  the  use  of  any  movable  rear  rudder  operated 
in  conjunction  with  any  wings  capable  of  being  presented  at  different  angles  of 
incidence  at  their  opposite  ends,  for  the  purpose  of  restoring  the  lateral  balance  of 
a  flying  machine  and  of  guiding  the  machine  to  right  or  left. 

The  words  "actuate  at  the  same  time,"  about  which  so  much  has  been 
argued,  can  be  interpreted  only  in  the  sense  that  there  is  a  device  which  per- 
mits of  the  movement  of  the  two  commands  at  the  same  time.  This  point 
once  established,  the  disassociation  of  the  elements  claimed  is  a  type  of  improve- 
ment. 

This  disassociation  must  in  principle  be  considered  as  a  dependent  of  the 
patent  of  1904,  since  this  improvement  is  a  natural  development  of  the  primi- 
tive invention,  proceeding  from  the  master  idea  in  which  it  had  its  origin,  and 
from  which  it  can  not  be  separated.  The  patentees  alone  have  the  right  to 
profit  by  it. 

The  outcome  in  this  country  appears  to  depend  entirely  upon 
whether  ailerons  or  wing  tips — independent  auxiliary  surfaces  between 


516 


AERONAUTICAL   PRACTICE  75 

the  planes,  as  in  the  Curtiss,  or  hinged  extensions  of  the  wings  them- 
selves, as  in  the  Farman — really  constitute  an  infringement  on  the 
principle  of  actually  warping  the  surfaces  of  the  wings  themselves. 
This  may  be  gathered  from  the  following  concise  statement  of  claims 
1,  2,  3,  4,  and  7  of  the  Wright  patent.  The  specifications  are  drawn 
to  cover  monoplanes,  biplanes,  and  machines  having  two  or  more 
superposed  surfaces. 

1.  In  a  flying  machine,  a  normally  flat  aeroplane  having  lateral  marginal 
portions  capable  of  movement  to  different  positions  above  or  below  the  normal 
plane  of  the  body  of  the  aeroplane,  such  movement  being  about  an  axis  trans- 
verse to  the  line  of  flight,   whereby  said  lateral  marginal  portions  may  be 
moved  to  different  angles  relatively  to  the  normal  plane  of  the  body  of  the 
aeroplane,  so  as  to  present  to  the  atmosphere  different  angles  of  incidence, 
and   means  for   so   moving   said   lateral   marginal   portions,   substantially   as 
described. 

2.  The  application  of  vertical  struts  near  the  ends  and  having   flexible 
joints. 

3.  Means  for  simultaneously  imparting  such  movement  to  said    lateral 
portions  to  different  angles  relatively  to  each  other. 

4.  Refers  to  the  movement  of  the  lateral   portions  on  the  same  side  to 
the  same  angle. 

7.  Means  for  simultaneously  moving  vertical  rudder  so  as  to  present  to 
the  wind  that  side  thereof  nearest  to  the  side  of  the  aeroplane  having  the 
smallest  angle  of  incidence. 

As  will  be  noted  in  the  opinion  of  Judge  Hazel,  the  Wright 
patent  will  undoubtedly  be  construed  broadly  and  not  narrowed 
down  to  constructional  detail  so  that  the  reference  to  "flat  planes," 
of  which  much  was  made  in  the  briefs  of  Curtiss  and  Paulhan  in  their 
defense  of  the  injunction  proceedings,  will  probably  not  affect  the 
decision  in  itself.  Both  defendants  strongly  contended  that  a 
machine  with  flat  planes  would  be  entirely  impracticable,  i.e.,  an 
inoperative  device,  thus  maintaining  that  the  present  Wright  machine 
is  not  the  apparatus  described  in  their  patent.  This  is  a  point  of 
the  greatest  importance  and  has  been  the  means  of  declaring  patents 
invalid  that  would  otherwise  have  been  of  considerable  value, 
such  as  the  patent  on  clincher  tires  for  automobiles.  Some  of  the 
more  recent  high-speed  racing  machines  built  in  France  during  1911 
have  been  equipped  with  supporting  surfaces  that  are  almost  flat  or 
at  least  sufficiently  so  to  substantially  fulfill  the  requirements  of  this 
claim  of  the  patent  under  the  broad  construction  accorded  it. 


517 


70 


AERONAUTICAL   PRACTICE 


This  accordingly  confines  the  points  at  issue  to  whether  sup- 
plementary surfaces,  either  independent  of  or  attached  to  the  wings 


Fig.  -10.      Diagram  of  Wright  Control  System,  Showing  Warping  of  Main  Planes 

themselves,  constitute  an  infringement  of  the  warping  device  of 
the  Wrights,  and  whether  the  simultaneous  operation  of  the  vertical 
rudder  in  conjunction  with  these  supplementary  surfaces,  regardless 


HOfflZOHTAL^STEADY/ftG 


VEffT/CAL   ff  UDDER 
Of£ffA  TED  BY  /fOCKMG 
WHEEL 


CABLf  ATTACHED  TO  YOKE 
/VfOUMD  AV/ATOR5  BODY 
BY  MOVJ/iG/ifS  BODY  FROM 
SJDf  TO  S/Ef.  THC  YOKE  13 
rtADf  TO  TkT  THE AILDTOH5 

//y  orros/TE  D/ft£CT/ons 


FiR.  41.      Diagram  of  Curtiss  Control  System,  ShowinR  Use  of  Ailerons  Swung  between 

Main  Planes 

of  how  it  may  he  carried  out,  is  an  infringement  of  the  functional 
correlation  of  these  parts  which  Judge  Hand  states  constitutes  the 
invention  of  the  Wright  Brothers. 


518 


AERONAUTICAL   PRACTICE 


77 


As  shown  by  the  drawing,  Fig.  40,  the  Wright  machine  is 
provided  with  means  for  operating  the  vertical  rudder  in  conjunc- 
tion with  the  warping  of  the  main  planes,  as  covered  by  claim  7  of 
the  patent.  Ability  to  move  the  hinged  lever  on  the  machines  in 
actual  use  in  two  directions  makes  it  possible  to  use  either  control 
independently  or  both  simultaneously. 

Fig.  41  shows  that  these  controls  are  separate  in  the  Curtiss 
machine,  but  they  naturally  can  be  employed  simultaneously  by 
the  aviator.  The  Farman  system  of  control  is  shown  in  Fig.  42, 
and  the  Bleriot  in  Fig.  43.  The  Wrights  regard  it  as  basic  that 


TH£A/LurOrtS  I4W/V 
MOVED  FffOff  5/DE  TO 
SID£AttD  THEHO/fl- 
ZOHTAL  /TUDDEff  WHEV 
PL/SHED  Off  PULLED 
SACK  AMD  fOffTH 


A/LE/TO/V 

/HACT/VE  ros/r/m 


TO  L/fT  Tfift  S/£>£ 
Of  WCH/NE  BY/M 
C/?EAS//YG  A/f? 


Fig.  42.      Farrnan  System  of  Control,  Showing  Use  of  Ailerons  Attached  to  Main  Planes 

both  controls  be  carried   out   together  to   attain  successful  flight, 
Wilbur  Wright  explaining  the  operation  of  turning  as  follows: 

In  making  a  turn  to  the  left,  the  left  side  of  the  machine  would  slow 
up  and  the  right  side  would  move  faster.  If  only  the  vertical  rudder  were 
employed  to  make  the  turn,  the  machine  would  skid  greatly  to  the  right, 
headway  would  be  lost  and,  at  this  point  in  the  turn,  the  machine  would  tend 
to  stand  on  its  right  side,  lose  support,  and  drop.  To  make  a  short  turn  to 
the  left  without  losing  headway,  the  practice  is  to  warp  the  right-hand  end  of 
the  plane  down  and  the  left-hand  end  up,  with  vertical  rudder  turned  to  the 
left,  it  being  necessary  to  heel  the  machine  to  the  left  to  prevent  skidding. 


519 


78 


AERONAUTICAL   PRACTICE 


It  is  claimed  to  be  possible  to  make  turns  of  great  radius  with- 
out warping  the  wings,  but  the  machine  would  skid  more  or  less 
and,  moreover,  would  not  be  entirely  safe.  Its  stability  would  be 
precarious.  In  making  a  short  turn  without  the  use  of  the  vertical 
rudder  in  conjunction  with  the  warping  of  the  wing  ends,  the  machine 
tends  to  turn  on  a  vertical  axis  like  a  corkscrew,  and  the  simul- 
taneous operation  of  both  essentials  is  necessary  to  overcome  this. 

In  view  of  the  flatly  contradictory  statements  made  in  the  briefs 
submitted  in  the  injunction  proceedings,  the  frank  opinion  of  Louis 
Bleriot,  France's  foremost  aeroplane  designer  and  builder,  con- 


W/tff 


H4ND  WHEEL  WMCH/3 
-ffOCffED  FffOM  SIDE  TO 
TO  WAfff  W/HGS 


L  £\/£ff 

Fig.  43.     Bleriot  Control  System  by  Warping  of  Main  Plane 

tained  in  a  letter  written  regarding  the  granting  of  the  injunction 
against  Paulhan  gives  an  inkling  of  what  the  views  of  other  unprej- 
udiced inventors  in  the  field  really  are: 

Concerning  the  Wright  patents  my  opinion  is  that  the  warping  of  the 
wings,  taken  in  itself,  is  public  property,  and  I  think  this  can  easily  be  shown. 
The  vertical  rudder  is  itself  public  property  and  it  is  only  the  combining  of 
these  two  effects — balancing  and  steering — in  a  single  lever  control  which  can 
with  some  show  of  reason  be  claimed  by  the  Wright  Brothers.  I  have  per- 
sonal reason  to  regret  that  they  did  not  confine  their  claim  to  this  single  lever, 
for  it  is  an  interesting  improvement  and  one  concerning  which  we  could  have 
established  an  understanding  with  the  Wrights  that  would  have  been  of  profit 
to  all  aviators. 

In  all  my  present  French  machines,  the  warping  of  the  monoplane  sur- 
face is  brought  about  with  the  left  hand,  while  the  steering  is  dependent  on 


520 


AERONAUTICAL   PRACTICE  79 

foot  control.  These  two  effects  are  entirely  independent  and  in  no  way  neces- 
sarily corrective,  as  called  for  in  the  Wright  patents;  on  the  contrary,  experi- 
ence shows  that  the  major  part  of  the  time  their  effects  should  be  added  to 
each  other  instead  of  being  corrective  of  each  other.  This  independence  of 
control  necessitates  a  somewhat  more  delicate  hand  and  a  longer  apprenticeship, 
but  one  which  the  present  uncompromising  attitude  of  the  Wrights  forces  me 
to  maintain.* 

I  have  gone  further :  In  view  of  their  threats  I  have  tried  to  do  away  com- 
pletely with  warping,  using  only  for  balancing  purposes  a  somewhat  larger 
vertical  keel.f  The  result  was  entirely  satisfactory:  I  was  in  this  manner 
able  to  fly  without  warping,  in  winds  as  strong  as  those  faced  by  the  Wrights. 
I  delivered  to  Paulhan  two  such  machines  for  his  American  trip  and,  in  his 
trials  at  Pau  prior  to  leaving  France,  he  flew  perfectly  without  any  warping 
device.  He  made  as  sharp  turns  as  previously  and  merely  had  to  use  a 
greater  tilt  when  doing  so. 

To  sum  up:  This  question  of  warping  about  which  so  much  fuss  has 
been  made,  and  which  seemed  to  be  a  sine  qua  non  condition  of  lateral  stability, 
proves  to  be  of  far  less  importance.  If  warping  renders  signal  service  in  keel- 
less  machines  of  wide  wing  area  such  as  the  Wright  machines,  it  becomes  a 
far  less  necessary  improvement  in  machines  of  small  breadth  of  wing,  provided 
with  keels,  and  is  entirely  needless  in  machines  with  vertical  partitions,  such 
as  the  Voisin  biplanes.  As  aeroplanes  will  tend  more  and  more  toward  increas- 
ing speed  and  diminution  of  breadth  of  wing,  the  question  of  warping  will 
more  and  more  lose  its  importance. 

I  merely  wish  to  say  that  it  was  regrettable  to  see  at  the  dawn  of  a  science 
(to  encourage  which  all  should  have  united  in  their  efforts),  inventors  make 
the  unjustifiable  claim  of  monopolizing  an  idea,  and,  instead  of  bringing  their 
help  to  their  collaborators,  prevent  them,  for  no  reason,  from  profiting  by 
some  ideas  which  they  should  have  been  happy  to  see  generalized. 

It  is  apparent  that  M.  Bleriot  is  laboring  under  the  same  errone- 
ous impression  regarding  the  threatened  monopoly  as  are  other 
aviators,  many  of  whom  have  reason  to  be  well  informed.  That 
this  monopoly  will  not  come,  even  after  the  Wright  patent  has 
been  declared  valid,  may  be  seen  from  the  statement  of  their  coun- 
sel, H.  A.  Toulmin,  made  in  answer  to  the  endless  criticism  aroused 
by  the  granting  of  the  preliminary  injunctions  early  in  1910. 

# 

The  Wright  Brothers  have  repeatedly  announced  their  willingness  to 
license  not  only  individuals  who  wish  to  fly  with  the  Wright  type  of  machine, 
but  also  to  license  exhibition  managers,  committees  promoting  exhibition 
meets  and,  in  fact,  anyone  who  wishes  to  use  for  any  purpose  a  Wright  machine 
or  an  infringing  machine.  Indeed  these  gentlemen  have,  to  my  knowledge, 
extended  a  helping  hand  again  and  again  to  other  experimenters.  They  have 


*This  statement  is  directly  contrary  to  Berget's  claim — "Conquest  of  the  Air," — that 
the  French  machines  may  be  controlled  by  amateurs  after  a  few  flights;  whereas  the  Wright 
machine  requires  a  long  apprenticeship. — ED. 

fSee  descriptions  of  special  types  of  American  machines  on  same  plan. — ED. 


521 


80  AERONAUTICAL  PRACTICE 

supplied  them  with  valuable  data  worked  out  by  themselves,  that  other  inven- 
tors might  produce  different  and  better  machines  if  they  could.  This  very 
fact  was  alluded  to  in  the  learned  opinion  of  Judge  Hazel  in  suit  against  the 
Herring-Curtiss  Company.  The  Wrights  have  gone  so  far  as  to  announce, 
and  the  fact  has  been  published,  that  even  though  an  experimenter  were  using 
a  Wright  machine  or  an  infringing  machine,  he  would  not  be  molested  so  long 
as  he  confined  his  work  to  experimentation  and  did  not  seek  to  get  money 
returns. 

The  chief  development  of  importance  during  1911,  where  the 
legal  situation  was  concerned,  was  the  granting  of  an  injunction  in 
favor  of  the  Wright  Brothers  against  Claude  Grahame  White,  by 
Judge  Hand,  sitting  in  the  United  States  Circuit  Court  for  the 
Southern  District  of  New  York.  So  far  as  White  personally  is  con- 
cerned, this  settles  the  validity  of  the  Wright  patent,  though  where 
the  patent  itself  is  concerned,  this  does  not  alter  its  status.  As  the 
result  of  the  injunction  White  can  not  fly  in  the  United  States 
without  permission  of  the  Wright  Brothers,  and  if  they  do  grant  the 
necessary  permission,  he  must  either  fly  a  Wright  machine,  or  pay 
royalty  on  the  one  he  uses,  while  the  decision  also  opens  the  way  for 
an  accounting  for  the  damages  accruing  from  White's  use  of  infringing 
machines  from  November,  1910,  or  even  earlier,  another  action  having 
been  started  for  that  purpose.  The  action,  favorably  ended  for  the 
Wrights  by  Judge  Hand's  opinion,  was  a  suit  for  infringement  and 
accounting  by  reason  of  the  defendant's  use  of  Farman  and  Bleriot 
machines  in  this  country,  claims  3,  7,  9,  14,  and  15  of  the  Wright 
patent  being  involved.  No  proofs  were  presented  by  the  defendant 
and  the  validity  of  the  Wright  patent  was  not  seriously  disputed. 
Judge  Hand,  among  other  things,  states: 

In  the  form  in  which  the  case  arises  there  can  not  be  any  substantial 
doubt  of  the  right  of  the  complainant  to  an  injunction.  The  defendant  has 
put  in  no  proofs  upon  any  of  the  issues  raised  in  the  answer  and  the  patent 
is  sustained  by  its  own  prima  facie  validity.  I  shall  adopt  the  same  interpreta- 
tion which  I  put  upon  it  in  The  Wright  Company  vs.  Paulhan,  and  hold  that 
the  fixed  connection  between  the  rudder  and  the  warping  mechanism  is  not 
an  essential  feature  of  the  claims,  but  that  the  only  connection  between  the 
two  may  be  made  by  the  intermediation  of  a  human  body  and  a  human  will. 
The  defendant,  while  not  conceding  the  validity  of  the  patent,  does  not  seri- 
ously challenge  it,  or  argue  that  his  biplanes  have  not  infringed  it.  I  have, 
therefore,  no  alternative  but  to  grant  an  injunction. 

It  may  be  another  year  or  two  before  the  Wright-Curtiss  action, 
which  is  the  only  suit  pending  that  has  the  validity  of  the  patent 


522 


AERONAUTICAL  PRACTICE  81 

as  its  issue,  will  be  decided  in  the  lower  court,  as  further  time  has 
been  granted  in  which  to  take  testimony  before  it  goes  to  trial  in 
the  United  States  District  Court  at  Buffalo.  As  there  will  undoubt- 
edly be  an  appeal,  regardless  of  which  of  the  litigants  is  favored  with 
a  decision,  it  may  be  several  years  before  the  patent  rights  of  the 
plaintiffs  are  actually  established. 

During  1912,  action  is  to  be  taken  generally  against  makers  and 
aviators  in  this  country  who  are  manufacturing  and  exhibiting  alleged 
infringing  machines.  This  is  not  the  legal  procedure  originally 
planned  by  the  Wright  Company,  but  one  that  has  been  forced  upon 
it,  more  or  less,  by  public  censure.  The  original  intention  was  to 
bring  infringement  suits  against  makers  or  users  of  the  principal  types 
of  machines,  such  as  Curtiss,  Farman,  and  Bleriot  only,  and  to 
obtain  as  early  an  adjudication  as  possible  for  the  benefit  of  the  art 
and  industry,  for  not  until  final  confirmation  or  dismissal  of  the 
Wright  claims  would  capital  be  likely  to  invest  in  aviation  nor 
would  the  public  buy  machines  of  the  types  involved.  The  progress 
of  the  actions  against  Paulhan,  against  Curtiss,  and  against  White 
has  already  been  outlined.  It  is  questionable,  in  case  injunctions 
are  granted,  as  would  appear  likely  in  view  of  the  White  decision, 
that  damages  could  be  collected  from  defendants  permanently  resi- 
dent in  France,  though  it  seems  probable  that  the  English  courts 
would  favorably  view  the  judgment  of  an  American  court  and 
compel  payment  of  the  claims  against  White. 

Criticism  was  quite  general  of  the  action  of  the  Wrights  in 
selecting  the  few  defendants  mentioned,  and  there  was  considerable 
wonderment  as  to  why  the  Moissant  aviators  were  not  prosecuted, 
why  Sopwith  was  allowed  to  import  and  fly  machines  in  this  country, 
and  why  Ovington,  Baldwin,  Willard,  and  the  large  number  of  lesser 
lights  who  are  killing  the  prospects  for  future  meets  and  exhibitions 
all  over  the  country  by  failing  to  satisfy  the  public  curiosity,  or  even 
to  fly  at  all  in  some  instances,  were  left  to  do  as  they  pleased. 
Actions  have  accordingly  been  begun  against  many  of  the  aviators 
in  question  and  still  others  will  be  sued.  The  policy  of  the  Wrights 
in  this  connection  is  made  clear  by  the  appended  statement  of 
F.  H.  Russell,  general  manager  of  the  Wright  Company. 

Our  first  desire  was  not  to  bother  the  general  public  until  it  could  be 
informed  -as  to  the  legal  status  of  the  Wright  patent,  but  with  such  rapid 


523 


82  AERONAUTICAL   PRACTICE 

developments  in  this  country,  and  with  the  coming  over  of  foreigners  who 
are  not  interested  in  development,  excepting  in  so  far  as  they  would  make 
money  to  take  away  from  the  country,  we  were  becoming  criticized  for  the 
very  policy  which  wre  considered  most  broad  and  liberal.  Then ,  too,  by 
refraining  from  these  further  suits,  we  might  be  considered  as  acquiescing,  to 
the  detriment  of  our  legal  position. 

Another  reason,  quite  as  important  as  the  popular  feeling  (above 
expressed),  which  has  altered  our  policy,  is  the  fact  that  manufacturers  and 
licensees  in  these  exhibitions  who  have  recognized  our  patents  and  paid  our 
royalties,  are  very  rightly  requesting  the  protection  in  their  business  which 
they  feel  the  patents  should  insure,  and  which  they  have  paid  for. 

Legislation.  The  practical  use  of  the  aeroplane  and  the  airship 
has  brought  with  it  new  legal  problems,  which  are  now  the  subject 
of  attention  in  several  countries.  In  view  of  its  leading  position  in 
this  field,  France  has  already  taken  the  first  step  by  adopting  a  code 
of  laws  to  regulate  aerial  navigation  in  that  country,  the  object  being 
to  protect  the  public  against  inconveniences  and  risks  which  may 
result  from  imprudent  and  daring  aviators,  quite  as  much  as  to  regu- 
late the  users  of  the  machines  themselves.  The  code  adopted  com- 
prises six  chapters  with  forty-two  provisions.  It  requires  all 
"airships"  (dirigible  balloons  or  aeroplanes)  to  bear  a  visible  regis- 
tration number,  and  to  carry  a  log  book  in  which  the  names  of  all 
persons  carried  and  the  times  and  places  of  departure  and  arrival 
are  entered.  No  explosives  are  to  be  transported  except  by  special 
permit,  while  wireless  and  photographic  apparatus  is  also  prohibited 
without  permission  from  the  minister  of  public  works.  Flights  over 
cities  and  crowds  are  prohibited  and  the  airship  must  alight  whenever 
officially  signaled  to  do  so,  though  just  what  the  signals  are  to  be 
has  not  been  settled.  Dirigibles  must  carry  "sailing  lights"  between 
sundown  and  sunrise,  exactly  the  same  as  in  marine  service,  i.  e.,  a 
white  headlight  and  red  and  green  lights  to  port  and  starboard, 
respectively.  Aeroplanes  have  been  given  temporary  permission  to 
carry  a  single  light,  but  it  must  show  white  ahead  and  red  and  green 
to  left  and  right,  similar  to  the  small  combination  motorboat  lights 
used  in  this  country. 

However,  American  law  is  based  upon  the  English  common  law 
and,  as  the  latter  differs  radically  from  the  French  code,  the  situation 
in  both  countries  where  aeronautics  is  concerned  is  totally  different. 
In  view  of  the  old  legal  maxim  that  ownership  of  the  land  extends 
to  the  center  of  the  earth  and  to  the  sky,  or  in  other  words,  indefi- 


524 


AERONAUTICAL   PRACTICE  83 

nitely  in  both  directions  from  the  surface,  there  would  appear  to  be 
no  public  right  to  the  atmosphere  at  all.  But  no  square  decision 
has  ever  been  made  on  this  point,  while  the  numerous  dicta  of  which 
it  has  been  made  the  subject  would  indicate  that  the  maxim  is 
rather  lightly  regarded,  it  having  been  referred  to  in  one  instance 
as  a  "fanciful  phrase."  But  it  is  only  when  the  possession  of  the  soil 
is  interfered  with  that  the  airman  is  likely  to  infringe  upon  the  rights 
of  property  owners.  That  point  of  view  is  taken  in  most  of  the 
European  codes.  For  example,  in  the  German  code  it  is  stated  that  a 
property  holder  can  not  prohibit  such  interferences  undertaken  at  such 
a  height  or  depth  that  he  has  no  interest  in  the  prevention. 

Probably  the  first  laws  to  be  enacted  in  this  country  will  con- 
cern human  safety  and  not  property.  In  view  of  the  accidents  that 
occurred  at  Paris  on  the  occasion  of  the  start  of  the  Paris-Madrid 
race  in  the  summer  of  1911,  it  seems  unlikely  that  air  craft  in  Europe 
will  be  permitted  to  fly  over  large  cities  or  towns  owing  to  the  possi- 
bility of  being  compelled  to  descend  because  of  a  crippled  motor  or 
lack  of  fuel.  On  the  other  hand,  the  open  country  and  navigable 
streams  will  doubtless  be  unrestricted. 

Forced  descents  may  perhaps  render  it  necessary  to  treat  the 
airman  more  leniently  than  is  possible  under  the  common  law.  In 
a  New  York  case  (Guille  vs.  Swan,  19  Johns.  381),  decided  in  1822, 
an  aeronaut  was  held  responsible  not  only  for  the  direct  damage  caused 
by  the  descent  of  his  balloon  into  a  garden,  but  even  for  the  conse- 
quential damage  caused  by  the  crowding  of  strangers  upon  the  prop- 
erty to  satisfy  theii^  curiosity.  Governor  (formerly  judge)  Simeon 
Baldwin  of  Connecticut  reviewed  the  problem  in  an  article  in  the 
American  Journal  of  International  Law  (1910)  in  which  he  raised  the 
question  as  to  whether  the  law  of  self-preservation  might  not  be 
invoked  by  the  airman  who  is  compelled  to  make  an  immediate 
landing  to  save  his  own  life  and  in  so  doing  accidentally  causes  the 
death  of  another.  Under  ordinary  circumstances,  he  considered  it 
advisable  to  indicate  by  some  simple  means  where  landing  was  pro- 
hibited and  where  permitted.  As  a  matter  of  general  policy  it  would 
not  seem  that  the  aviator  should  be  made  to  pay  more  than  for  the 
direct  damage  for  which  he  himself  has  been  responsible. 

To  avoid  these  forced  descents,  and  to  insure  as  careful  control 
of  air  craft  as  possible,  licenses  to  navigate  the  air  will  undoubtedly 


525 


84  AERONAUTICAL   PRACTICE 

be  necessary.  Most  of  the  bills  pending  before  State  Legislatures  in 
this  country  and  which  will  probably  be  enacted  generally  during 
the  next  year  or  two  provide  for  such  licenses  as  one  of  their  most 
important  features.  In  this  country,  it  is  questionable  whether  the 
States  should  be  permitted  to  issue  such  licenses  in  preference  to  the 
Federal  Government,  though  attempts  to  have  a  law  of  this  nature 
passed  to  control  automobiles  have  extended  over  a  number  of  years 
without  success.  With  aeroplanes  traveling  anywhere  from  40  to 
90  miles  an  hour,  several  of  the  smaller  States  could  be  traversed  in 
the  course  of  a  day.  The  conditions  are  so  radically  different  and 
the  distances  covered  so  great  that  the  present  practice  of  one  State 
recognizing  the  automobile  licenses  of  others  would  mean  the  practical 
nullification  of  any  State's  license  act.  The  right  of  the  Federal 
Government  to  license  air  craft  would  appear  analogous  to  that  of 
regulating  navigation  on  coastal  as  well  as  inland  waters. 

Questions  of  aerial  international  politics  have  already  given 
congresses  which  have  met  in  Europe  no  little  concern  but,  on  the 
whole,  there  appears  to  be  a  tendency  to  apply  the  principles  of 
maritime  law  to  air  craft.  The  American  Political  Science  Associa- 
tion has  suggested  that  the  right  of  the  air  craft  of  one  nation  freely 
to  traverse  the  air  space  of  another  might  be  compared  with  that  of 
the  vessel  of  one  State  freely  to  navigate  the  waters  of  a  co-riparian 
State.  The  abortive  convention  drafted  by  the  International  Con- 
ference on  aerial  navigation  in  1910  was  based  entirely  upon  the 
provisions  of  international  maritime  law.  There  are  the  same 
requirements  as  to  registration  and  nationality  of  the  vessels,  the 
same  method  of  determining  the  fitness  of  the  craft  and  the  com- 
petence of  its  navigators,  and  the  same  regulations  applying  to  the 
sojourn  of  air  craft  in  distress.  Provision  is  also  made  for  the  keeping 
of  logs,  customs  supervision  of  the  atmosphere,  the  right  of  police, 
the  regulation  of  passenger  and  freight  traffic,  the  prohibition  of 
navigation  in  certain  zones  in  the  vicinity  of  fortifications;  and  there 
is  even  a  tendency  to  incorporate  a  principle  analogous  to  the 
three-mile  neutral  zone  of  maritime  law,  but  there  appears  to  be  no 
agreement  as  to  the  height  of  the  zone  as  yet. 

Customs.  Aeroplanes  have  also  caused  more  or  less  trouble  to 
the  customs  authorities  of  various  countries,  entirely  aside  from  their 
adaptability  to  the  dark  ways  of  smugglers.  For  instance,  Mexico 


526 


AERONAUTICAL   PRACTICE  85 

classes  the  flying  machine,  when  imported  complete,  under  the  head 
of  "articles  not  specially  mentioned  of  iron,  steel,  or  tin  plate, 
etc.,"  while  Canada  places  the  aeroplane  in  the  same  category  as 
"telephone  and  telegraph  instruments,  batteries,  motors,  dynamos, 
and  electrical  apparatus  not  otherwise  provided  for."  In  India  the 
Governor  General  is  given  authority  to  make  regulations  concerning 
the  admission  of  aeroplanes,  or  to  prohibit  their  importation  entirely. 
The  duty  in  this  country  on  a  complete  machine  is  naturally  affected 
by  the  fact  that  it  is  equipped  with  a  motor,  bringing  it  under  the 
head  of  "manufactures  of  metal,"  which  makes  the  rate  on  the  entire 
machine  45  per  cent  ad  valorem,  substantially  adding  to  the  cost  of 
a  foreign  machine  in  this  country, 

MILITARY  IMPORTANCE  OF  AEROPLANE  AND  DIRIGIBLE 

Whenever  a  new  development  receives  a  great  impetus,  as  has 
been  the  case  with  aeronautics  generally  within  the  past  few  years,, 
prophecies  abound.  The  day  when  the  aeroplane  will  be  utilized 
in  a  similar  manner  to  the  automobile  appears  to  be  so  far  distant, 
at  present,  that  the  imagination  naturally  reverts  to  something 
more  immediate — and  that  something  has  taken  the  form  of  the 
military  importance  of  the  aeroplane  and  the  dirigible.  Owing  to 
the  great  expenditure  involved  in  the  construction  and  maintenance 
of  the  latter,  its  chief  destiny  appears  to  lie  in  this  direction.  When 
the  submarine  torpedo  was  perfected,  prophecies  to  the  effect  that 
here,  at  last,  was  an  instrument  that  would  make  war  impossible 
in  future,  were  freely  made;  the  submarine  boat  and  the  Dread- 
naught  type  of  battleship  met  with  similar  acclaim.  Despite  the 
lack  of  fulfillment  that  has  attended  these  prophecies,  they  have 
been  dragged  out  again  and  made  to  serve  in  the  same  role  for  the 
aeroplane.  As  was  naturally  to  be  expected,  much  that  is  erroneous 
and  misleading  has  appeared  regarding  the  latter  as  well  as  its  bulkier 
and  more  costly  comrade-in-arms,  the  dirigible.  That  the  "aerial 
navy,"  however,  is  already  an  established  fact  will  be  evident  from 
the  following,  which  represents  the  strength  of  this  "new"  arm  of  the 
various  military  establishments  of  the  world. 

Attitude  of  Military  Powers.    France  maintains  4  dirigibles  of  an 
aggregate  of  395  horse-power,  and  38  aeroplanes,  mostly  of  the  mono- 


527 


86  AERONAUTICAL   PRACTICE 

plane  type;  Germany  has  7  dirigibles  of  1,160  horse-power,  and  24 
aeroplanes,  mostly  Wright  biplanes  of  German  manufacture;  England 
has  3  dirigibles  of  365  horse-power,  and  3  aeroplanes,  all  biplanes; 
Russia  has  one  70-horse-power  dirigible  and  6  monoplanes;  Italy  has 
one  100-horse-power  dirigible  and  8  Bleriot  monoplanes;  Spain  has  one 
100-horse-power  dirigible  and  no  aeroplanes;  Austria  has  one  70- 
horse-power  dirigible  and  4  biplanes;  and  the  United  States  maintains 
one  Baldwin  dirigible  of  30  horse-power,  and  one  Wright  biplane. 
This  brief  statement  gives  some  idea  of  the  relative  strength  of  the 
various  nations  at  the  end  of  1910,  and  in  the  case  of  France  plans 
had  already  been  made  to  increase  the  equipment  by  more  than  50 
per  cent,  while  in  Germany  activity  in  the  same  direction  is  also 
very  much  to  the  fore.*  Japan  and  even  Turkey  are  experimenting 
with  both  types  of  machines  with  a  view  to  making  them  a  part  of 
their  military  service.  The  backwardness  of  the  United  States  in  this 
respect  is  explained  by  the  great  advantages  of  its  natural  position, 
but  it  is  anticipated  that  more  interest  will  soon  be  taken  in  an 
aeronautical  division  of  the  army,  while  experiments  to  make  the 
aeroplane  an  auxiliary  of  the  navy  have  already  been  undertaken. 
Considerable  interest  has  been  aroused,  however,  by  the  success- 
ful flights  of  an  aeroplane  from  the  deck  of  a  cruiser  to  the  shore, 
and  by  the  unusual  feat  of  alighting  on  a  specially-built  platform  on  a 
man-of-war  and  again  leaving  it.  The  flights  of  Curtiss  in  a  machine 
designed  to  alight  on  or  run  over  the  surface  of  the  water  have  added 
to  the  interest,  so  that  Congress  has  been  induced  to  appropriate  the 
sum  of  $125,000  for  further  experiments  along  this  and  similar  lines, 
it  being  apparent  that  the  aeroplane  will  be  of  great  importance  as 
an  auxiliary  to  the  navy,  Fig.  44.  Owing  to  the  ease  with  which  a 
machine  can  be  taken  apart  and  put  together  again,  it  can  be  stowed 
in  a  very  limited  space  and  can  be  quickly  assembled  for  action. 
As  the  deck  of  a  vessel,  however,  would  not  afford  sufficient  unen- 
cumbered space  for  either  starting  or  alighting,  it  is  quite  evident 
that  the  aeroplane  evolved  for  this  purpose  will  be  one  capable  of 
starting  from  the  water  and  alighting  on  it — or  rather  one  that  is 
able  to  run  and  alight  on  either  water  or  land. 


*These  figures  have  since  been  greatly  increased.  France  has  placed  large  orders  for 
aeroplanes  and  dirigibles.  England  and  Germany  are  also  increasing  their  aerial  "navies," 
while  the  United  States  has  acquired  additional  Wright  and  Curtiss  biplanes,  also  Curtiss 
hydroaeroplanes,  but  it  is  difficult  to  give  definite  figures. — ED. 


528 


AERONAUTICAL   PRACTICE 


87 


England,  also,  is  awakening  to  the  importance  of  the  new  arm, 
but  appears  to  lean  somewhat  to  the  German  view  which  at  first 
regarded  the  dirigible  of  paramount  importance,  though  Germany 
has  since  greatly  increased  her  aeroplane  fleet.  During  1910,  there 


Fig.  44.     The  New  Naval  Scout    the  Fourth  Military  "Arm" 

was  constructed  at  the  ship-building  plant  of  Vickers'  Sons  &  Maxim, 
Barrow  in  Furness,  England,  a  huge  dirigible  for  military  purposes. 
The  greatest  secrecy  was  maintained  regarding  the  details,  but  it 
was  planned  to  be  the  largest  dirigible  ever  attempted,  exceeding  in 
size  any  of  the  Zeppelin  monsters  thus  far  constructed.  It  was  known 


529 


88 


AERONAUTICAL   PRACTICE 


as  Naval  Airship  No.  1  and  was  equipped  with  motors  of  400  horse- 
power. The  envelope  was  covered  with  a  metallic  coating  to  serve 
as  a  protection  and  to  make  the  gas  bag  rigid.  It  had  a  carrying 
capacity  sufficient  to  take  a  complement  of  34  men,  but  at  first  only 
six  officers  and  men  were  required,  a  special  crew  being  in  training 
to  man  it  under  expert  supervision.  The  armament  consisted  of  a 
special  type  of  aerial  weapon.  A  second-class  cruiser  was  assigned 
to  special  duty  as  a  convoy  for  the  huge  airship,  but  the  latter  was 
wrecked  the  first  time  an  attempt  was  made  to  take  it  out  of  its  shed. 
The  length  of  this  huge  dirigible  was  510  feet,  the  diameter  at  the 


Fig.  45.     Paulhan's  All-Steel  Aeroplane  for  Military  Use 

greatest  girth  was  48  feet,  and  the  gas  capacity  was  706,336  cubic  feet. 
The  envelope  was  made  of  silk  and  was  divided  into  seven  sections. 
Power  was  derived  from  two  sets  of  eight-cylinder,  V-type, 
water-cooled,  four-cycle  Wolseley  engines,  designed  to  run  at  500 
r.  p  .m.,  driving  three  propellers  which  were  expected  to  give  the 
airship  a  speed  of  45  miles  an  hour — a  rate  of  travel  not  hitherto 
approached.  To  each  of  these  engines  was  connected  eight  sheet- 
metal  tanks,  each  tank  having  a  capacity  for  2,000  gallons  of  gasoline, 
making  a  total  fuel  capacity  of  32,000  gallons.  These  tanks  were 
welded  together  in  airtight  sections,  insuring  the  ability  of  the  airship 
to  keep  its  motors  running  should  an  accident  or  injury  occur  to  any 
particular  section.  The  precaution,  however,  entailed  the  addition 


530 


AERONAUTICAL   PRACTICE 


89 


of  300  yards  of  aluminum  piping  for  the  connections.  The  frame- 
work was  constructed  of  duralumin,  a  new  alloy  of  aluminum  which  is 
said  to  be  much  lighter  and  stronger  than  that  at  present  in  general  use. 

The  British  War  Department  has  also  lately  purchased  one  of 
the  new  type  of  aeroplane,  Fig.  45,  designed  by  Paulhan  and  described 
in  detail  later. 

Adaptability  to  War.  In  most  of  the  prophecies  on  the  subject 
the  use  of  air  craft  in  war  is  regarded  as  being  something  quite  novel 
and  of  entirely  recent  development.  This,  of  course,  is  true  of  the 


Fig.  46.     Krupp  Guns  for  Protection  Against  Air  Crafts,  Showing  Open  Ammunition 

Magazines 

aeroplane,  but  ever  since  Napoleon  formed  the  first  military  balloon 
corps  in  1793,  practically  all  the  first-class  powers  have  utilized 
aeronautics  in  war  to  the  extent  to  which  development  permitted 
at  the  time.  Napoleon  used  balloons  in  Egypt,  though  with  small 
success;  the  Austrians  employed  them  before  Venice  in  1849,  the 
Russians  at  Sebastopol  in  1854-55,  the  French  in  the  Italian  cam- 
paign of  1859,  the  United  States  army  in  the  Civil  War,  the  French 
during  the  Siege  of  Paris,  1870-71,  the  British  in  the  Indian  and 
African  campaigns,  and  both  sides  in  the  Russo-Japanese  War. 


531 


90 


AERONAUTICAL   PRACTICE 


At  first,  the  captive  balloon  was  used  altogether  for  scouting 
purposes,  but  since  the  advent  of  the  dirigible  the  simple  balloon  has 
become  obsolete  for  anything  but  purely  sporting  purposes.  Up 
to  two  years  ago,  the  relative  importance  of  this  arm  of  the  service 
depended  entirely  upon  the  number  of  dirigible  balloons  maintained, 
and  artillery  designers  have  been  very  active  in  adapting  their  guns 
to  firing  at  angles  never  before  thought  necessary.  This  has  been  the 
case  particularly  in  Germany  where  the  Krupp  works  have  been  con- 
ducting a  series  of  experiments  in  firing  at  balloons  with  specially- 


Fig.  47.     Krupp  Guns  for  Protection  Against  Air  Crafts 

designed  guns,  some  of  which  are  shown  in  Figs.  46  and  47.  In 
addition  to  scouting,  or  rather  discovering  the  enemy's  position 
without  endangering  men  in  the  latter  service,  the  balloon  has  most 
frequently  been  employed  for  directing  artillery  fire,  it  having  proved 
particularly  valuable  for  this  purpose  both  in  our  own  Civil  War, 
and  in  the  Boer  War  in  South  Africa  where  a  captive  balloon  was 
equipped  with  a  searchlight  and  used  at  night.  The  history  of  its 
employment,  however,  may  be  found  in  detail  in  works  on  the  sub- 
ject and  would  be  out  of  place  here,  except  as  a  precedent  for  the 
development  that  is  now  taking  place. 


532 


AERONAUTICAL   PRACTICE  .  01 

The  rapid  development  of  the  aeroplane  and  its  facility  of  action 
more  than  justifies  its  ever-increasing  application  to  military  opera- 
tions by  the  first-class  powers.  Such  feats  as  Roll's  return  trip  across 
the  English  Channel,  Chavez's  flight  over  the  Alps,  Tabuteau's  six- 
hour  flight,  Breguet's  flight  with  twelve  passengers,  McCurdy's 
sending  wireless  telegrams  from  a  Curtiss  biplane  while  in  flight, 
Moisant's  trip  through  country  totally  new  to  him  by  compass 
guidance,  McCurdy's  trip  from  Key  West  to  Havana,  and  Ely's 
flight  from  a  cruiser  to  shore  and  back  are  all  accomplishments  that 
could  be  put  to  considerable  advantage  in  a  state  of  actual  warfare. 
Behind  all  the  imaginative  prophecies  of  airships  eliminating  navies, 
decimating  armies,  and  utterly  destroying  forts  and  cities  by  dropping 
explosives,  there  is  a  foundation  of  fact  which  will  be  utilized  as 
developments  warrant  it.  All  of  the  extravagant  stories  of  the 
absolute  invincibility  of  the  aeroplane  have  not  been  the  product  of 
untrammeled  creators  with  ample  imagination,  though  the  per- 
sistence with  which  they  have  been  repeated  has  led  to  replies  in  kind 
which  have  shown  a  scarcely  higher  appreciation  of  the  true  value 
of  the  aeroplane.  Even  such  a  high  authority  as  the  late  Rear  Admiral 
Robley  D.  Evans  is  reported  to  have  expressed  an  opinion  that 
strikingly  reveals  how  little  is  really  known  concerning  the  possi- 
bilities of  the  aeroplane. 

It  is  only  natural  that  those  experienced  in  the  service  should 
express  contempt  for  anything  lauded  as  being  so  infinitely  superior 
to  the  methods  of  warfare  in  which  they  are  skilled.  Nor  is  it  any- 
thing new — the  advent  of  the  torpedo  and  the  submarine  boat 
brought  forth  a  similar  greeting.  Some  of  the  stories  regarding  the 
possibility  of  annihilating  battleships  and  armies  through  dropping 
explosives  on  them  were  hardly  worthy  of  anything  better.  It  is  a 
matter  of  common  knowledge  that  to  do  any  great  damage,  an  explo- 
sive must  be  confined.  An  aerial  bombardment  could  scarcely  be 
expected  to  do  as  much  damage  as  a  naval  action  of  the  same  class, 
and  it  would  be  far  more  difficult  to  carry  on.  There  could  be  no 
penetration  to  the  missiles  and  their  damage  would  be  confined  to 
blowing  holes  in  the  surfaces  of  streets  and  the  roofs  of  houses,  or 
in  the  case  of  a  man-of-war,  in  damaging  its  superstructure.  Talk 
of  this  nature  in  connection  with  the  destruction  of  battleships  led 
Rear  Admiral  Evans  to  attempt  to  show  how  easily  an  aeroplane 


533 


92 


AERONAUTICAL   PRACTICE 


could  be  destroyed  from  the  deck  of  a  ship,  Fig.  48.  According  to 
his  theory,  firing  could  begin  at  long  range — say,  10,000  yards,  or 
between  five  and  six  miles.  As  the  machine  approached,  more 
guns  could  be  utilized,  and  the  aviator  who  would  have  the  daring 
to  approach  a  battleship  under  such  a  hail  would  be  daring  indeed. 
But  anyone  who  has  seen  an  aeroplane  at  a  distance  of  .five  to 
six  miles  can  fully  realize  that  nothing  short  of  a  miracle  could  ever 
cause  it  to  be  struck.  It  is  the  merest  speck  in  the  sky,  even  at  a 


Fig.  48.     Illustrating  Possible  Use  of  Small  Machine  Guns  Against  Aeroplanes 

mile  or  so,  and  can  best  be  compared  to  the  size  of  a  common  housefly 
a  hundred  yards  away.  It  is  almost  impossible  to  follow  it  with  the 
eye,  and  once  lost  it  is  extremely  difficult  to  pick  up  again.  Add 
to  this  the  fact  that  it  is  traveling  anywhere  from  50  to  60  miles 
an  hour  or  better — speeds  at  which  a  moving  object  has  never  been 
shot  at  before,  and  the  chances  of  striking  it  would  seem  to  be  about 
zero  minus.  Yet  Rear  Admiral  Evans  is  reported  as  stating  that  it 
would  prove  an  easy  mark  for  a  12-inch  gun.  The  futility  of  making 


534 


AERONAUTICAL  PRACTICE  93 

such  an  attempt  would  be  on  a  par  with  trying  to  shoot  a  fly  with  a 
sporting  rifle  at  a  hundred  feet  while  the  insect  was  flying  faster 
than  the  marksman  could  follow  its  movements  through  the  sights. 

Operations  in  France.  Military  Maneuvers.  On  the  other  hand 
while  few,  who  are  in  a  position  to  know,  entertain  the  idea  that 
aeroplanes  will  ever  supersede  battleships,  or  put  an  end  to  war, 
they  do  know  that  they  are  destined  to  play  an  important  part  in 
the  war  game  of  the  future,  and  most  nations  are  now  seriously 
developing  this  new  auxiliary  as  an  adjunct  to  their  military  estab- 
lishments. What  can  be  accomplished  with  the  aid  of  this  branch 
of  the  service  designed  to  operate  in  the  third  dimension,  is  probably 
best  illustrated  by  brief  reports  of  the  French  maneuvers  held  in 
the  fall  of  1910  and  that  of  1911  and  extending  over  a  week  in  each 
year.  Owing  to  the  extraordinary  progress  of  military  aeronautics 
they  were  carried  out  on  an  unprecedented  scale.  Each  opposing 
general  had  at  his  command  well-organized  detachments  of  dirigibles 
and  aeroplanes  with  the  necessary  stations,  repair  shops,  and  a  large 
and  well-trained  personnel.  In  1910,  fifteen  air  craft  took  part, 
four  aeroplanes  being  assigned  to  each  corps  and  three  being  assigned 
to  the  staff  headquarters,  together  with  four  dirigibles,  while  the 
1911  maneuvers  were  upon  the  most  elaborate  and  impressive  scale 
ever  witnessed,  the  number  of  machines  employed  being  greatly  in- 
creased over  the  previous  year. 

Three  aeroplane  stations  were  established  at  different  points 
some  distance  apart,  while  immense  sheds  were  erected  for  the 
dirigibles  Colonel  Renard,  Liberte,  and  Zodiac  at  the  Camp  Militaire, 
while  another  enormous  "hangar"  or  loft  was  erected  for  the  Clement- 
Bayard  II  at  Issy-les-Moulineaux,  the  famous  French  aviation  field. 
This  shed  was  almost  400  feet  long  by  100  feet  high  by  70  feet  wide 
and  though  merely  a  temporary  structure  cost  200,000  francs,  or 
about  $40,000.  A  building  was  also  put  up  to  manufacture  hydrogen 
gas  by  a  new  secret  process  employing  powdered  ferro-silicon  treated 
with  caustic  potash.  The  gas  thus  produced  is  said  to  be  much  purer 
than  is  possible  with  the  usual  commercial  methods  and  proved  very 
satisfactory  in  service. 

The  maneuvers  began  with  a  trip  by  the  Clement-Bayard  II 
of  a  little  over  two  hours  and  at  an  average  elevation  of  about  1,000 
feet;  during  the  entire  time  it  was  in  wireless  communication  with 


535 


94  AERONAUTICAL   PRACTICE 

the  Eiffel  Tower  and  the  military  headquarters.  On  the  following 
day  numerous  flights  were  made  for  purposes  of  reconnoissance, 
the  aviators  making  flights  of  some  distance  and  reporting  back  in 
a  very  short  time  with  the  information  gained,  despite  the  heavy 
wind  that  prevailed.  The  results  of  observations  made  by  the  aerial 
scouts  were  such  as  to  force  the  commanders  to  change  their  plans 
of  battle  twice.  Notwithstanding  a  wind  of  26  miles  an  hour  that 
was  frequently  accompanied  by  rain,  numerous  flights  were  made 
the  next  day,  Latham  circling  the  entire  series  of  the  enemy's  posi- 
tions in  a  heavy  rainstorm  and  promptly  returning  to  report  the 
information  he  had  gained. 

After  this,  the  Clement-Bayard  II  made  a  reconnoissance  of 
an  hour's  duration,  landed,  and  immediately  afterward  started  for 
Paris  to  place  the  two  armies  in  communication.  The  flight  was  made 
at  an  average  height-  of  1,200  feet  and  the  distance  of  75  miles  was 
made  with  seven  passengers  in  two  hours  and  seventeen  minutes. 
Constant  communication  was  maintained  by  wireless  with  Paris 
(Eiffel  Tower)  and  during  the  trip  a  number  of  carrier  pigeons  belong- 
ing to  the  various  divisions  were  released.  The  smaller  dirigibles, 
La  Liberte  and  Colonel  Renard,  also  made  a  number  of  trips.  During 
the  latter  half  of  the  week,  the  second  part  of  les  grandes  manoeuvres 
were  carried  out  in  the  course  of  which  numerous  flights  were  made 
to  carry  dispatches  distances  as  great  as  50  miles  for  purposes  of 
observation  and  the  like.  In  each  case,  the  aviator  carried  a  military 
observer  with  him,  usually  an  officer  of  engineers,  and  the  infor- 
mation obtained  subsequently  proved  to  be  startlingly  accurate. 
Although  four  of  the  machines  were  disabled  in  service,  their  value 
as  scouts  and  dispatch  bearers  could  scarcely  be  underestimated. 

On  the  next  to  the  last  day  of  the  maneuvers,  the  weather 
improved  and  there  was  afforded  the  unprecedented  sight  of  no  less 
than  four  dirigibles  and  eight  aeroplanes  in  the  sky  at  once — an 
unequaled  opportunity  to  test  marksmanship  with  the  new  automo- 
bile-mounted, rapid-fire  gun,  had  the  use  of  the  latter  been  possible. 
The  Clement-Bayard  II  started  in  fine  weather  for  the  last  trip  of 
the  maneuvers  on  the  final  day,  but  was  almost  destroyed  by  a 
storm  before  landing.  The  airship  was  caught  by  a  violent  wind 
and  sent  along  at  a  speed  greater  than  that  of  an  express  train  pass- 
ing below,  while  the  lightning  played  so  fiercely  against  the  steel 


536 


AERONAUTICAL  PRACTICE 


95 


sides  of  the  car  and  the  wireless  apparatus  that  it  was  feared  that 
the  hydrogen  would  be  ignited, 

The  successful  carrying  out  of  military  maneuvers  on  such  an 
extended  scale  with  the  aid  of  airships  and  aeroplanes  may  be  regarded 
as  marking  the  advent  of  a  new  era  in  armaments.  The  French 
army  has  officially  adopted  the  aeroplane  as  a  ''fourth  arm"  and  as 
the  result  of  the  trials  in  question  has  decided  to  greatly  increase  its 


Fig.  49.     Portable  Type  of  Monoplane  for  Military  Use 

equipment.  No  less  than  twenty  Farman  biplanes  and  ten  Bleriot 
racing  monoplanes  were  ordered,  which  would  bring  the  total  to 
sixty  machines  in  service.  The  new  aeroplanes  are  designed  to  have 
a  radius  of  action  of  150  miles,  lifting  capacity  sufficient  to  carry 
three  men  and  50  pounds  of  weight  besides,  and  are  to  be  equipped 
with  a  second  or  reserve  motor.  They  are  of  the  portable  type  as 
shown  by  Figs.  49  and  50.  In  addition,  three  military  flying  schools 
have  been  established  and  are  to  be  augmented  by  four  more.  To 


537 


96 


AERONAUTICAL   PRACTICE 


each  of  the  new  stations  will  be  assigned  twelve  machines  and  twenty 
aviators.  Stations  are  also  to  be  established  along  the  coast,  those 
mentioned  all  being  inland. 

Military  Aeroplane  Tests.  For  the  selection  of  more  aeroplanes 
for  this  purpose,  an  open  competition  was  held  in  the  latter  part  of 
1911.  The  general  conditions  to  be  fulfilled  by  the  competing 
machines  were  as  follows:  To  be  built  entirely  in  France  of  French 
materials;  to  be  able  to  fly  186  miles  in  a  closed  circuit  without  a 
stop,  and  with  a  useful  load  of  660  pounds  in  addition  to  the  fuel, 
oil,  and  water  necessary  for  the  trip;  to  carry  three  persons  corn- 


Fig.  50.     Portable  Bleriot  Mounted  for  Quick  Transportation 

fortably — the  pilot,  mechanic,  and  an  observer;  to  have  a  mean 
speed  of  36  miles  per  hour;  to  be  capable  of  alighting  without  accident 
on  stubble  fields,  plowed  ground,  sowed  or  clover  land;  and  to  be 
able  to  arise  easily  therefrom;  also  to  be  capable  of  easy  transpor- 
tation, whether  dismantled  or  not,  by  road  or  rail,  and  to  be  easily 
and  rapidly  put  together  without  minute  adjustments. 

After  having  satisfied  a  committee  that  it  was  entitled  to  enter 
the  competition,  each  machine  was  put  to  a  series  of  severe  elimina- 
tion tests,  those  passing  the  latter  being  entitled  to  enter  the  final 
test  for  classification.  In  the  elimination  tests,  the  machine  was 
weighed  and  all  parts  stamped.  Any  part  could  be  replaced  during 


538 


AERONAUTICAL   PRACTICE  97 

the  tests  by  an  exact  duplicate,  but  no  modifications  were  allowed, 
except  in  the  case  of  propellers  and  wheels.  It  was  necessary,  how- 
ever, to  repeat  the  entire  test  from  the  beginning  in  case  a  part  was 
replaced.  Each  maker  was  compelled  to  declare  the  amount  of  gas 
and  oil  required  for  the  flight  of  186  miles,  and  only  this  amount  was 
provided.  The  first  test  was  a  cross-country  flight  carrying  660 
pounds  useful  load,  landing  in  a  clover  field  between  two  flags  225 
feet  apart.  Each  machine  was  then  required  to  arise  from  the  same 
spot,  circle,  and  re-alight  on  the  same  ground.  It  was  then  dis- 
mantled and  returned  to  the  starting  point  by  road.  The  same  test 
was  then  repeated,  first  by  alighting  upon  and  rising  from  stubble 
ground,  and  then  from  a  plowed  field,  the  machine  being  dismantled 
after  each  test  and  returned  to  the  starting  point  by  road  as  in  the 
first  test.  This  was  followed  by  a  speed  trial,  making  a  round  trip 
of  36  miles,  which  was  also  a  test  of  fuel  and  oil  consumption.  In 
case  there  was  a  shortage  of  less  than  10  per  cent,  the  test  had  to  bs 
repeated;  where  the  shortage  exceeded  this,  the  machine  was  elimi- 
nated from  the  competition.  In  the  altitude  test,  each  aeroplane 
had  to  rise  1,875  feet  in  15  minutes  or  less,  carrying  a  load  of  660 
pounds.  This  test  had  to  be  successfully  performed  twice  and  con- 
cluded the  preliminary  trials.  Out  of  an  entry  of  thirty  machines, 
only  nine  qualified — as  follows:  1  Nieuport  monoplane,  2  Deper- 
dussin  monoplanes,  2  Breguet  biplanes,  1  H.  Farman  biplane,  1 
Savary  biplane,  and  2  M.  Farman  biplanes. 

The  final  trial,  termed  the  "classification  test,"  comprised  a 
round-trip  flight  of  184  miles  without  alighting,  and  carrying  a  useful 
load  of  660  pounds,  the  contestants  being  allowed  three  trials  each. 
The  machines  were  started  five  minutes  apart  in  an  order  determined 
by  drawing  lots.  The  race  was  one  of  the  most  interesting  in  the  history 
of  aviation  and  was  successfully  completed  by  all  but  one  of  the  nine 
machines.  As  a  result,  the  remaining  eight  were  classified  as  follows: 

(1)  Nieuport  monoplane,   100-horse-power  Gnome  motor,  average  speed 
70.2  m.p.h. 

(2)  Breguet  biplane,  140-horse-power   Gnome  motor,  average  speed  57 
m.p.h. 

(3)  Deperdussin    monoplane,     100-horse-power    Gnome  motor,  average 
speed  52.5  m.p.h. 

(4)  Breguet    biplane,  100-horse-power  Gnome  motor,  average  speed  52 
m  p.h. 


539 


98  AERONAUTICAL   PRACTICE 

(5)  H.  Farman  biplane  100-horse-power  Gnome  motor,  average  speed 
50.6  m.p.h. 

(6)  M.  Farman  biplane,  70-horse-power  Renault  motor,  average  speed 
45.6  m.p.h. 

(7)  M.  Farman  biplane,  70-horse-power  Renault  motor,  average  speed 
43.3  m.p.h. 

(8)  Savary  biplane,  70-horse-power  Labor  motor,  average  speed  40.2 
m.p.h. 

In  accordance  with  the  original  program,  the  makers  of  the 
first  machine  were  awarded  a  bonus  of  $20,000,  an  order  for  10 
machines  at  $8,000  each,  and  a  bonus  of  $100  for  each  kilometer  in 
excess  of  60  made  by  the  winning  machine,  this  bonus  amounting 
to  $56,900,  so  that  the  Nieuport  won  $156,900;  the  Breguet  $83,000, 
and  the  Deperdussin  $59,500. 

It  will  be  noted  that,  throughout  the  maneuvers  in  question, 
no  mention  is  made  of  bomb-dropping  about  which  there  has  been 
so  much  talk,  but  which  is  not  regarded  so  highly  in  military  circles. 
Work  of  this  kind  is  to  be  totally  ignored  in  the  curriculum  of  the 
schools  in  question.  How  small  would  be  the  damage  done  by  aero- 
plane high  explosive  attack  was  shown  by  the  Japanese  bombard- 
ment of  the  Russian  fleet  in  Port  Arthur.  The  fire  of  the  11-inch 
siege  guns,  throwing  a  quarter-ton  explosive  shell,  was  directed  by 
a  skilled  observer  on  a  hill  commanding  the  harbor,  and  the  pro- 
jectiles with  their  highly-explosive  contents  rained  down  upon  the 
decks  of  the  ships  with  the  greatest  accuracy,  falling  almost  vertically. 
The  entire  Russian  fleet  was  sunk,  not  by  the  shell  fire,  but  actually 
by  the  Russians  themselves,  as  subsequent  examination  revealed, 
which  also  showed  that  the  damage  done  by  the  projectiles  was 
astonishingly  small.  If,  then,  the  falling  of  a  500-pound  explosive 
shell  from  a  height  of  two  miles  directly  upon  the  deck  of  a  ship, 
caused  so  little  injury,  the  possibility  of  destroying  a  war  vessel  by 
means  of  small  hand-launched  bombs  is  practically  nil.  But  for 
scouting,  taking  photographs,  especially  with  the  telephoto  camera, 
and  for  sending  information  by  wireless,  the  aeroplane  is  an  arm 
whose  importance  can  not  be  denied.  Had  such  an  aid  been  available 
in  1898,  Admiral  Sampson  would  have  known  within  an  hour  that 
Cervera's  fleet  was  resting  quietly  in  Santiago  harbor,  instead  of  use- 
lessly blockading  the  entrance  to  the  harbor  for  a  month,  and  the 
unfortunate  Schley-Sampson  controversy  would  never  have  occurred. 


540 


AERONAUTICAL  PRACTICE  99 

Aeroplane  Maneuvers  in  United  States.  Ely's  Flight  from  the 
Birmingham.  That  the  aeroplane  may  be  of  as  much  assistance  to 
the  naval  branch  of  the  service  as  the  army  is  already  appreciated, 
as  witnessed  by  Ely's  attempted  flight  in  a  Curtiss  biplane  from  the 
deck  of  the  scout  cruiser  Birmingham  to  the  Norfolk  Navy  Yard, 
some  30  miles  from  the  place  where  he  left  the  ship.  This  was  under- 
taken in  the  latter  part  of  November  and,  as  the  result  of  its  successful 
outcome,  attempts  were  made  to  rise  from  the  deck  of  a  war  vessel 
and  return  to  it.  A  wood  platform  25  feet  wide  and  85  feet  in 
length  was  built  on  the  forecastle  of  the  Birmingham  to  provide  a 
run  for  the  machine.  This  platform  was  given  a  downward  slope 
and  projected  slightly  beyond  the  bow  of  the  cruiser,  as  will  be  noted 
in  the  illustrations  of  a  later  flight  in  San  Francisco  harbor.  Ely's 
machine  was  assembled  and  tested  at  the  Jamestown,  Virginia,  race 
track  and  then  transferred  to  the  war  vessel  by  one  of  the  government 
derrick  lighters.  Despite  squalls  of  wind  and  rain,  it  was  decided 
to  attempt  a  flight  and,  starting  his  engine  during  a  calm  spell,  Ely 
ran  down  the  sloping  platform  at  high  speed  and  shot  over  the  bow 
directly  toward  the  water.  As  the  biplane  left  the  platform  it  settled 
rapidly  till  it  struck  the  water  with  a  splash,  which  was  thought  to 
terminate  the  experiment.  Instead,  however,  the  machine  rose 
without  difficulty  to  a  height  of  about  150  feet  and  headed  for  shore, 
which  was  reached  without  any  difficulty.  Ely  attributed  his  down- 
ward plunge  to  a  faulty  movement  of  the  control  wheel.  When  the 
machine  struck  the  water,  the  propeller  was  damaged  and  the  spray 
so  clouded  the  aviator's  goggles  that  it  was  only  with  difficulty  he 
could  see  to  make  his  way  toward  the  land.  Owing  to  the  accident, 
a  descent  was  made  at  Willoughby's  Point,  two  and  one-half  miles 
distant,  instead  of  continuing  to  Norfolk  as  originally  planned. 
Examination  showed  that  the  damage  to  the  propeller  was  slight  and 
the  flight  could  have  been  resumed,  or  an  attempt  made  to  return 
to  the  vessel,  had  this  been  desired. 

The  significant  point  of  this  performance  is  the  fact  that  the 
aeroplane  started  under  its  own  power  from  a  vessel  at  rest  with  but 
an  85-foot  run  and  a  30-foot  drop.  Considering  the  bad  weather 
conditions,  this  was  an  excellent  performance.  A  speedy  cruiser  offers 
the  great  advantage  that  she  could  be  headed  into  the  wind,  or  even 
where  there  was  no  wind,  could  steam  fast  enough  to  allow  an  aero- 


541 


100 


AERONAUTICAL   PRACTICE 


plane  to  rise  from  its  deck  without  any  preliminary  run,  while  in  alight- 
ing the  aeroplane  could  simply  hover  above  the  vessel  in  motion  and 
drop  gently  to  her  deck.  In  place  of  the  cumbersome  platform  adopted 
for  the  experiment  in  question,  all  that  would  be  needed  would  be 
troughs  for  the  wheels  to  run  in  and  these  could  be  stowed  away  when 
not  in  use.  For  that  matter,  a  special  starting  derrick,  such  as  that 
originally  employed  by  the  Wright  Brothers,  could  be  used  readily. 


Fig.  51.     Ely  Making  a  Landing  on  the  Deck  of  the  U.  S.  S.  Pennsylvania 

The  design  of  the  aeroplane  itself  would  also  have  to  be  modified 
to  correspond  to  the  conditions.  The  wheels  would  undoubtedly  be 
necessary  to  make  it  possible  to  use  the  machine  on  land,  but  it 
should  also  be  provided  with  hydroplane  floats,  similar  to  those 
employed  on  the  Fabre  marine  aeroplane,  to  permit  the  machine  to 
alight  upon  and  again  start  from  the  surface  of  the  ocean.  The 
possibility  of  an  aeroplane  leaving  and  returning  to  a  war  vessel, 
such  as  the  scout  cruiser  Birmingham,  at  will  and  with  certainty 
should  undoubtedly  increase  the  usefulness  of  vessels  of  this  type. 


542 


AERONAUTICAL   PRACTICE 


101 


Ely  received  a  prize  of  $500  for  his  flight  from  the  United  States 
Aeronautical  Reserve,  and  a  similar  prize  is  offered  for  a  flight  of  this 
kind  from  a  merchant  vessel.  Two  attempts  to  make  the  latter  were 
undertaken  at  New  York,  the  object  being  to  return  from  a  point 
50  miles  at  sea  with  mail,  but  on  each  occasion  a  gale  of  wind  made 
carrying  out  the  experiment  impossible.  Curtiss  himself  was  to 
have  made  the  flight  and  even  went  so  far  as  to  have  the  starting 
platform  built. 

Ely  in  San  Francisco  Harbor.     A  few  months  later,  January 
17,  1911,  Ely  made  a  flight  in  a  Curtiss  biplane  from  the  land  and 


Fig.  52.     Ely's  Machine  on  the  Deck  of  the  U.  S.  S.  Pennsylvania 

alighted  easily  on  the  deck  of  the  U.  S.  S.  Pennsylvania,  anchored  in 
the  harbor  of  San  Francisco,  Figs.  51  and  52.  This  was  preceded 
by  a  12-mile  flight  from  the  aviation  field  where  the  start  was  made. 
A  special  platform  120  feet  long  by  40  feet  wide  had  been  erected 
on  the  after-deck  of  the  vessel,  canvas  shields  being  placed  at  each 
side  to  prevent  the  machine  going  overboard  in  case  it  did  not  alight 
squarely  on  the  platform.  Ropes  were  stretched  across  the  platform 
and  made  fast  to  bags  of  sand  at  either  end  to  arrest  the  progress  of 
the  aeroplane,  in  case  the  skids  with  hooks  provided  especially  for 
this  purpose  did  not  work  as  anticipated.  Ely  left  the  field,  climbed 
23000  feet,  crossed  the  San  Bruno  hills  at  a  great  height,  and  then 


543 


102  AERONAUTICAL   PRACTICE 

descending,  circled  the  shipping  in  the  harbor.  He  headed  straight 
for  the  Pennsylvania,  shut  off  the  motor  while  still  at  a  considerable 
height,  glided  down  to  the  platform  and  landed  with  perfect  ease, 
the  machine  coming  to  a  dead  stop  before  running  more  than  a  third 
of  the  distance  allowed.  So  little  trouble  was  experienced  in  making 
the  landing  accurately  that  Ely  was  of  the  opinion  that  he  could 
carry  it  out  successfully  in  nine  cases  out  of  ten,  given  moderate 
weather  conditions.  Where  the  ship  was  under  way  and  headed 
directly  with  the  wind,  it  could  undoubtedly  be  performed  even  in 
brisk  weather.  After  a  reception  on  board,  Ely  returned  to  the  avia- 
tion field  in  sixteen  minutes.  As  this  was  the  second  time  he  had 
started  a  flight  from  the  deck  of  a  naval  vessel,  he  was  more  accus- 
tomed to  the  conditions  and  soared  off  with  great  ease. 

Following  these  experimental  flights,  Curtiss  perfected  the  hydro- 
aeroplane and  also  devised  a  practical  method  of  launching  it  from 
the  ship  on  flexible  wire  cables,  as  described  in  the  article  on  the 
"Hydroaeroplane."  Curtiss  also  made  flights  to  and  from  a  cruiser  in 
San  Diego  Harbor,  the  aeroplane  and  aviator  being  hoisted  aboard 
after  alighting  on  the  surface  alongside.  The  United  States  navy 
has  acquired  several  of  these. machines  and  has  inaugurated  an  aero- 
nautical department,  a  number  of  the  navy  officers  having  become 
aviators  at  the  Curtiss  school. 

Bomb-Dropping  Performance.  During  the  two  days  preceding 
Ely's  flight,  practical  tests  of  the  aeroplane  for  scouting  and  bomb- 
dropping  were  undertaken  at  the  aviation  field.  Lieutenant  Myron 
Crissey  of  the  Coast  Artillery  dropped  a  special  shrapnel  bomb  from 
a  height  of  550  feet  while  flying  in  a  Wright  machine  piloted  by 
Parmalee.  The  bomb  consisted  of  a  very  thin  shell  of  brittle  white 
cast  iron,  loaded  with  black  powder  and  bullets  and  fitted  with  a  per- 
cussion cap.  Its  weight  was  about  8  pounds.  Lieutenant  Crissey 
succeeded  in  dropping  it  with  considerable  accuracy  and  it  tore  a 
large  hole  in  the  ground,  scattering  its  contents  round  a  radius  of 
about  50  yards.  This  is  the  first  time  that  an  actual  bomb  was  ever 
used  in  experiments  of  this  nature  and  it  is  believed  that  it  would 
be  a  comparatively  simple  matter  to  hit  a  battleship  from  a  height 
as  great  as  3,000  feet,  where  the  aeroplane  itself  would  be  safe  from 
attack  to  a  very  great  extent.  For  this  purpose,  however,  it  would 
appear  to  be  more  destructive  to  cavalry  or  infantry. 


544 


AERONAUTICAL   PRACTICE 


103 


Scouting  Operations.  To  ascertain  the  value  of  the  aeroplane 
for  scouting,  flights  were  made  by  Lieutenant  George  Kelly  of 
the  13th  United  States  Infantry  with  Walter  Brookins  in  a  Wright 
biplane.  He  made  sketches,  drew  maps,  and  took  six  photographs 
of  the  surrounding  country,  but  failed  to  locate  a  body  of  troops 
that  had  left  the  Presidio  Military  Reservation  a  few  hours  before. 
This  is  the  first  time  that  an  aeroplane  had  been  utilized  for  military 
scouting  purposes  in  this  country,  although  employed  to  a  considerable 
extent  in  this  role  abroad  in  military  maneuvers,  where  the  same 


Fig.  53.     Real   Scouting   Service   by   Lieutenant   Foulois  in   a   Wright   Biplane 

inability  to  distinguish  troops  in  the  field  has  also  been  noted.  Several 
errors  in  reporting  the  character  of  the  different  objects  and  landmarks 
seen  were  also  noted,  from  which  it  is  apparent  that  the  aerial  scout 
will  require  special  training  and  experience  in  order  to  be  of  value 
to  his  commander,  as  some  of  the  errors  in  question  were  of  a  nature 
that  would  have  resulted  disastrously  had  the  information  been 
acted  upon  in  real  warfare.  This  is  not  only  the  case  when  the  coun- 
try is  viewed  from  the  swift-flying  aeroplane,  but  likewise  applies  to 
the  dirigible,  the  two  airships  employed  for  scouting  during  the  Ger- 
man army  maneuvers,  in  the  fall  of  1910,  having  failed  grievously. 


545 


104  AERONAUTICAL   PRACTICE 

One  crew  led  its  command  into  an  ambuscade,  while  the  other  fell 
into  the  hands  of  the  enemy  through  the  failure  of  the  motor. 

In  connection  with  the  French  military  maneuvers,  a  special 
test  was  arranged  to  learn  the  effect  that  would  be  produced  on  a 
troop  of  cavalry  by  the  sudden  appearance  of  an  aeroplane  above  it. 
For  this  purpose  a  Hanriot  monoplane  was  flown  immediately  over- 
head and  the  horses  were  all  but  stampeded  by  the  sight  of  the  huge 
bird-like  object  and  the  noise  of  the  motor.  As  the  first  encounter 
of  the  horses  with  a  flying  man  almost  put  them  to  rout,  regular  drills 
have  been  held  since  to  accustom  them  to  the  sight. 

Actual  War  Scouting.  The  closest  approach  to  scouting  in 
actual  warfare  thus  far  carried  out  has  been  in  connection  with  the 
rebellion  in  Mexico,  in  February,  1911.  R.  F.  Collier  loaned  the 
War  Department  his  new  Wright  biplane  and  Lieutenant  Foulois 
was  commissioned  to  fly  it  above  the  Mexican  border  during  the 
hostilities,  Fig.  53.  There  are  1,400  miles  of  border  to  be  patrolled 
and  the  government  called  for  volunteer  aviators  to  perform  this 
duty.  In  response,  Charles  K.  Hamilton  gave  his  services  and,  on 
February  10,  he  crossed  the  Rio  Grande  from  El  Paso,  Texas,  and 
reconnoitered  at  an  altitude  of  1,000  feet  above  Juarez,  locating  a 
body  of  Mexican  troops. 

Curtiss  and  His  Hydroaeroplane.  Another  test  simulating 
actual  war  conditions,  were  the  flights  of  Glenn  II.  Curtiss  in  his 
hydroplane  machine  from  the  surface  of  the  bay  alongside  the 
U.  S.  S.  Pennsylvania.  He  made  a  short  scouting  trip  and,  on  his 
return,  alighted  on  the  water  alongside  the  cruiser  as  easily  as  if  he 
were  landing  on  shore.  These  trials  were  made  shortly  after  the 
experimental  tests  of  this  machine  mentioned  in  connection  with 
a  description  of  its  construction.  Their  principal  object  was  to 
demonstrate  to  the  War  Department  that  an  aeroplane  can  be  made 
an  auxiliary  of  the  modern  man-of-war  without  the  necessity  of 
carrying  cumbrous  platforms  on  the  ship  itself  in  order  to  provide 
a  starting  and  landing  place.  Instead,  the  aeroplane  may  be  stowed 
on  the  superstructure  and  dropped  into  the  water  by  one  of  the 
cranes  in  the  same  manner  as  the  launches  are  handled,  though  the 
weight  is  naturally  but  a  fraction  of  that  of  the  latter.  Its  spread 
of  wing  does  not  involve  any  inconvenience,  as  even  with  the 
present  construction  the  aeroplane  may  be  readily  dismantled  and 


546 


AERONAUTICAL   PRACTICE  1Q5 

packed  in  small  compass,  the  operation  of  reassembling  it  requiring 
only  about  an  hour,  while  later  designs  made  especially  with  naval 
service  in  view  will  undoubtedly  render  it  possible  to  do  much 
better.  In  fact,  there  appears  to  be  no  reason  why  a  folding  type 
of  machine  can  not  be  evolved,  making  it  possible  to  put  it  in  com- 
mission for  a  flight  at  very  short  notice.  The  problem  of  launching 
has  since  been  solved  by  allowing  the  aeroplane  to  slide  down 
inclined  cables  as  described  in  the  article  on  the  "Hydroaeroplane." 
Italian  Operations.  To  try  out  its  aerial  equipment,  the  Italian 
military  authorities  put  one  of  its  airships  to  a  severe  test.  This 
was  Dirigible  No.  2,  which  was  sent  from  Rome  to  Venice,  a  distance 
of  230  miles,  crossing  the  Apennines  above  the  Via  Maggio  Pass, 
which  necessitated  rising  to  an  altitude  of  6,500  feet  and  occasioned 
the  loss  of  a  large  quantity  of  ballast  and  fuel.  One  stop  was  made 
for  propeller  repairs  after  having  traveled  90  miles,  and  other  stops 
were  made  in  the  two  following  days,  requiring  four  days  in  all  to 
make  the  trip,  though  the  actual  running  time  did  not  exceed  twenty- 
four  hours.  The  Italian  army  has  also  made  considerable  use  of 
the  aeroplane  in  its  campaign  against  the  Turks. 

GUNS  FOR  AERIAL  WARFARE 

Coincident  with  the  development  of  the  dirigible  and  the  aero- 
plane as  a  fourth  arm  to  the  military  establishments  of  most  civilized 
countries,  serious  efforts  have  been  directed  toward  the  evolution 
of  an  arm  particularly  adapted  to  bringing  down  these  ships  of  the 
air.  The  great  difficulty  of  hitting  an  airship  makes  the  usual  methods 
of  warfare  totally  inadequate.  The  fire  of  infantry  and  even  that 
of  machine  guns  is  of  little  use,  despite  their  momentary  mass 
effect,  because  of  the  limited  range  and  effectiveness  of  the  projectiles 
and  the  impossibility  of  observing  their  flight.  Field  and  siege  guns 
can  not  be  elevated  sufficiently  and  howitzers  are  deficient  in  range 
and  rapidity  of  fire.  All  these  classes  of  artillery  are  lacking  in  proper 
horizontal  angular  range  and  visibility  of  projectiles,  their  deficiencies 
having  been  proven  by  experiment. 

Special  guns  are  therefore  required  and  no  little  attention  is 
being  given  their  design  at  the  moment.  Various  types  of  such  guns 
have  already  been  developed  by  Ehrhardt,  Krupp,  Schneider, 
Skoda,  Vickers-Maxim,  and  others  abroad  and  in  this  country  as 


547 


106  AERONAUTICAL   PRACTICE 

well.  The  latter  have  been  constructed  in  the  American  govern- 
ment arsenals,  but  so  far  there  has  been  comparatively  little  interest 
in  the  subject  here.  Two  guns  of  American  make — one  a  2-inch  30 
caliber,  'and  the  other  a  3-inch,  both  mounted  on  wheeled  carriages, 
were  tried  without  success  against  captive  balloons,  in  1909.  One 
of  these  was  the  McClean-Lissack  automatic  rapid-fire  gun,  which 
was  mounted  on  a  3-ton  Packard  truck,  the  tests  being  carried  out 
at  Cleveland,  Ohio,  under  Lieutenant-Colonel  O.  W.  Lissack  of  the 
Ordnance  Department,  U.  S.  A.  The  gun  fired  3-pound  shells  at  the 
rate  of  100  per  minute,  the  range  being  3.5  miles,  but  as  the  ordinary 
shells  were  employed,  their  flight  could  not  be  followed  by  the  eye. 
Shots  were  tried  with  the  brakes  of  the  car  set  and  also  released, 
there  being  no  shock  felt  in  the  former  instance,  winle  only  a  slight 
movement  due  to  the  recoil  was  noticeable  in  the  latter. 

Because  of  its  speed,  weight,  and  strength,  the  automobile  is 
particularly  adapted  not  only  for  carrying  light  guns  of  this  type, 
but  also  for  providing  a  platform  from  which  they  can  be  fired  with 
a  reasonable  degree  of  accuracy.  Indeed  the  artillery  motor  car, 
armor-plated  and  carrying  a  gun  bolted  directly  to  its  chassis,  is  the 
natural  counterpart  of  the  familiar  armored  train,  and  quite  a  num- 
ber of  armored  and  semi-armored  automobiles  carrying  aerial  guns 
have  been  developed  abroad  during  the  last  year  or  two,  Fig.  47. 

Guns  employed  for  attacking  airships  or  flying  machines  must 
possess  a  maximum  elevation  of  at  least  70  degrees,  a  horizontal 
angular  range  of  360  degrees,  and  must  further  be  capable  of  rapid 
handling.  In  Ehrhardt's  5-centimeter  (2-inch)  automobile  gun,  an 
attempt  is  made  to  satisfy  these  requirements  by  aiming  the  gun, 
which  is  supported  at  its  center  of  gravity,  with  the  aid  of  a  shoulder 
rest  to  which  the  sights  are  attached.  This  method  gives  a 
maximum  elevation  of  70  degrees.  The  gun  is  mounted  in  an  armored 
turret  with  a  lateral  range  of  60  degrees  to  right  and  left,  the  turret 
itself  forming  part  of  a  completely  armored  automobile.  The  same 
gun  is  also  mounted  on  a  semi-armored  car,  giving  the  gun  a  horizontal 
range  round  a  complete  circle. 

For  this  purpose,  Krupp  has  developed  guns  of  2.6-,  2.8-,  3-, 
and  4:2-inch  caliber,  with  the  trunnions  close  to  the  breech  and  having 
a  maximum  elevation  of  75  degrees.  As  employed  on  automobiles, 
ships,  and  fortifications,  the  guns  are  mounted  on  carriages  which 


548 


AERONAUTICAL   PRACTICE  107 

rotate  on  pivots,  while  for  field  use  a  wheel  carriage  with  a  two-part 
axle,  the  halves  of  which  are  attached  by  hinge  joints  to  the  front  of 
the  long  carriage,  is  employed.  The  rear  end  of  the  carriage  is  pivoted 
to  a  rail  resting  on  the  ground.  If  both  wheels  are  brought  in  front 
of  and  locked  beneath  the  gun,  the  latter  can  be  revolved  entirely 
round  the  pivot  so  as  to  point  in  any  direction  by  turning  the  wheels 
by  hand.  Small  changes  of  direction  are  obtained  by  means  of  an 
upper  carriage  which  can  be  turned  5  degrees  to  the  right  or  left.  The 
durability  of  this  construction  has  been  proved  by  extensive  trials. 

The  Schneider  weapon  is  a  1.9-inch  60  caliber  gun  mounted  in 
an  armored  turret  carried  on  a  completely  armored  automobile.  The 
gun  can  be  elevated  70  degrees,  while  the  turret  can  be  revolved 
round  a  complete  circle.  The  Skoda  is  a  1.5-inch  70  caliber  gun  (cali- 
ber in  this  connection  refers  to  the  length  of  the  gun)  with  a  maximum 
elevation  of  80  degrees.  The  Vickers  firm,  which,  according  to  report, 
has  brought  out  a  6-inch  field  howitzer  suitable  for  use  against 
airships,  has  also  produced  a  1.9-inch  3-pounder  gun  designed  for 
use  on  fortifications,  ships,  and  automobiles.  A  maximum  elevation 
of  90  degrees  is  claimed  for  this  gun,  which,  like  Krupp's,  has  its 
trunnions  near  the  breech  and  is  elevated  by  a  rack  and  pinion. 

The  aiming  mechanism  of  a  gun  employed  against  airships  must 
be  such  as  to  enable  the  gun  pointer  to  follow  every  movement  of 
the  swiftly  flying  adversary.  "With  Ehrhardt's  gun,  this  is  effected 
by  sighting  as  with  a  rifle.  Krupp  employs  two  parallel  connected 
telescopes,  with  verticals  and  reflecting  eye  pieces.  One  man  aims 
the  gun  with  the^  aid  of  one  telescope;  another,  using  the  second 
telescope,  elevates  the  gun  and  fires  at  the  most  favorable  moment, 
without  oral  consultation  with  his  partner.  On  steeply  sloping  land, 
the  elevation  required  for  a  given  range  can  not  be  obtained  accurately 
from  any  published  tables,  so  the  telemeter  is  used  instead.  The 
necessary  rapidity  of  fire  is  obtained  with  a  self-closing  breech, 
while  great  range  and  accuracy  are  secured  by  the  employment  of 
an  unusually  long  gun  and  high  muzzle  velocities. 

In  airship  warfare,  the  question  of  ammunition  is  particularly 
important.  Shrapnel  is  not  well  suited  to  the  purpose.  With  a  large 
number  of  bullets  and  fragments  the  gas  bag  may  be  cut,  allowing 
the  gas  to  escape;  but,  while  serious  damage  may  thus  be  done  to 
airships  of  the  flexible  and  semi-rigid  types  in  which  the  gas  is  con- 


549 


108  AERONAUTICAL   PRACTICE 

fined  under  considerable  pressure  in  order  to  give  stiffness,  several 
of  the  separate  gas  bags  of  the  rigid  type  might  be  pierced  without 
bringing  it  down.  Nor  can  complete  success  be  reasonably  expected 
by  shrapnel  connected  by  chains  8  to  10  inches  long,  as  employed 
in  the  Italian  experiments,  or  from  shrapnel  with  rotating  blades 
and  fuses  for  the  purpose  of  cutting  the  bag  and  igniting  the  gas. 
An  additional  difficulty  in  the  employment  of  shrapnel  is  involved 
in  determining  the  proper  length  of  time  at  which  to  set  the  fuse, 
which  does  not  agree  with  the  tabular  time  of  flight  corresponding 
to  either  the  measured  distance  of  the  object  of  attack  or  the  distance 
deduced  from  the  angle  of  fire.  The  setting  of  the  time  fuse,  there- 
fore, requires  calculation,  which  is  incompatible  with  rapid  firing. 
The  fuse  also  tends  to  burn  very  irregularly  in  the  upper  atmospheric 
strata  of  -varying  density  which  the  projectile  may  have  to  traverse. 

The  most  promising  method  of  attack,  therefore,  is  apparently 
to  endeavor  to  strike  the  airship  directly  with  shells  and  destroy  it 
by  their  explosion  and  the  scattering  of  their  fragments.  Ehrhardt 
has  devised  a  shrapnel  shell  provided  with  a  fuse  for  the  ignition  of 
the  balloon  gas.  Krupp's  shell  has  a  contact  exploder  sensitive  enough 
to  be  operated  by  impact  on  the  envelope  of  the  airship,  which  it 
penetrates  before  exploding  in  the  interior.  In  the  gun,  this  very 
sensitive  exploder  is  prevented  from  going  off  by  a  mechanical  device. 
A  special  slow-burning  fuse  reveals  the  course  of  the  projectile  through 
the  air  by  its  light  at  night  and  a  heavy  trail  of  smoke  by  day. 

In  this  connection,  it  is  appropriate  to  refer  briefly  to  the  method 
of  firing.  As  the  hostile  airship  is  usually  visible  only  for  a  short 
time  and  sometimes  moves  very  swiftly,  it  can  not  be  hit  by  direct 
aiming,  even  with  the  easily-observed  fire  shells.  In  order  to  utilize 
fully  the  few  favorable  moments,  a  number  of  shots  are  fired  in  rapid 
succession,  varying  slightly  in  direction  and  elevation  but  aimed  in 
general  accordance  with  the  measured  or  estimated  distance  with 
proper  allowance  for  the  slope  of  the  land,  and  corrections  based  on 
observations  of  the  visible  flight  of  the  successive  shots. 

The  diameters  of  the  guns  mentioned  vary  from  1.5  to  4.2  inches. 
But  the  effectiveness  of  such  a  small  arm  as  the  Skoda  gun  with  its 
1.5-inch  diameter  and  firing  a  projectile  weighing  only  1.7-pounds 
is  questionable,  and  the  same  remark  applies  to  the  1.9-inch  Schneider 
and  Vickers-Maxim  guns.  The  diameters  most  suitable  for  field  work 


550 


AERONAUTICAL   PRACTICE  109 

appear  to  be  those  between  2.4  and  3  inches,  as  they  combine  the 
requisite  mobility  of  the  gun  with  an  effective  explosive  action,  and 
also  allow  shrapnel  to  be  employed.  Although  shrapnel  appears  to 
be  ineffective  against  airships,  as  already  pointed  out,  the  possibility 
of  employing  it  makes  the  gun  useful  for  other  field  work.  Krupp 
specifies  a  gun  of  4.2-inch  caliber  for  naval  and  fortification  use. 
In  addition  to  these  technical  requirements,  certain  tactical 
qualities  are  also  requisite.  Guns  employed  for  aerial  warfare  must 
possess  great  mobility  in  order  that  they  may  be  rapidly  trans- 
ported from  place  to  place  in  attacking  scouts  of  the  air.  The  auto- 
mobile appears  to  meet  every  requirement.  As  it  can  be  made  strong 
enough  for  all  military  purposes,  it  allows  the  employment  of  a  central 
pivot  mounting  especially  well  adapted  for  guns  employed  against 
airships;  it  can  carry  armor  and  can  also  transport  the  gunners  and 
ammunition  rapidly.  An  automobile  thus  armed,  equipped,  and  pro- 
tected by  armor,  is  so  heavy,  however,  that  its  speed  can  not  greatly 
exceed  30  miles  an  hour,  so  that  it  would  hardly  be  capable  of  pur- 
suing airships  traveling  with  a  favorable  wind  which  would  bring 
their  speed  beyond  its  reach. 

WIRELESS    TELEGRAPHY   IN   AERONAUTICS 
WIRELESS  ON  DIRIGIBLES 

Early  Experiments  on  Balloons.  It  will  be  apparent  that  one  of 
the  most  valuable  features  of  the  use  of  the  dirigible  and  the  aero- 
plane in  warfare  isithe  possibility  of  communicating  with  headquar- 
ters by  wireless  telegraphy,  which  means  the  instant  reception  of 
information  gained  by  scouting  parties.  Not  long  after  the  inven- 
tion of  sending  messages  through  the  air  became  a  reality,  Professor 
Slaby  demonstrated  that  wireless  signals  emitted  by  a  land  station 
can  be  received  by  a  balloon,  floating  freely  in  the  air.  The  experi- 
ments were  carried  out  in  conjunction  with  the  maneuvers  of  the 
Prussian  balloon  corps,  and  since  then  experiments  have  been  made 
successfully  in  other  countries.  The  balloon  Condor,  which  made 
an  ascension  near  Brussels  in  the  latter  part  of  1909,  maintained 
uninterrupted  communication  with  the  station  on  the  Brussels 
Palais  de  Justice,  and  also  caught  signals  sent  from  the  Eiffel  Tower 
at  Paris,  180  miles  distant.  Prior  to  this,  Professor  Hergesell  had 


551 


110  AERONAUTICAL  PRACTICE 

already  demonstrated  the  great  value  of  the  application  of  wireless 
telegraphy  to  balloons  by  controlling  the  valves  of  unmanned  sounding 
balloons  (small  balloons  sent  aloft  for  tire  purpose  of  carrying  meteor- 
ological instruments),  at  heights  extending  to  ten  miles,  by  wireless 
impulses.  The  receivers  of  the  balloons  were  tuned  to  different  wave 
lengths,  so  that  the  valve  of  any  one  balloon  could  be  opened  and  that 
particular  balloon  brought  down  at  will. 

In  a  series  of  experiments  made  with  the  German  military  bal- 
loon Gross  II,  in  the  autumn  of  1908,  messages  were  successfully 
sent  from,  as  well  as  to,  the  airship,  the  first  balloon  wireless  stations 
being  constructed  according  to  the  Telefunken  system.  It  was 
proved  by  preliminary  experiments  in  the  balloon  shed  that  the  dan- 
ger of  igniting  the  contents  of  the  gas  bag  by  sparks  emitted  from  the 
wireless  apparatus  could  be  averted  by  taking  suitable  precautions. 
This  danger  is  least  with  airships  of  the  flexible  and  semi-rigid  types, 
in  which  the  gas  bag  possesses  very  few  metallic  parts  that  could 
draw  sparks  from  the  highly  charged  aerial  which  is  used  for  sending 
and  receiving  the  flashes  from  the  air.  The  suspension  of  the  car  of 
the  Gross  by  hempen  ropes  insured  the  complete  insulation  of  the 
electrical  apparatus  from  the  gas  bag,  and  all  parts  at  which  sparks 
were  formed  were  enclosed  in  gas-tight  envelopes.  For  military 
reasons,  the  details  of  these  experiments  were  not  made  public,  but 
the  results  are  said  to  have  been  very  satisfactory. 

These  experiments  have  proved  that  electromagnetic  waves 
are  propagated  to  great  heights  in  the  atmosphere  and  that  the  part 
played  by  the  earth  in  wireless  telegraphy  is  far  less  important  than 
has  been  assumed.  Thus,  one  of  the  principal  theoretical  objections 
to  the  application  of  wireless  to  airships  has  been  shown  to  be  falla- 
cious. In  the  German  army  maneuvers  of  1909,  the  Gross  II 
demonstrated,  for  the  first  time,  the  practical  utility  of  wireless  teleg- 
raphy on  a  scouting  balloon.  The  Zeppelin  airship  which  took  part 
in  the  maneuvers  did  not  possess  this  advantage.  Subsequently, 
the  Zeppelin  III  was  equipped  with  wireless  apparatus  and  it  was 
shown  that  even  with  a  rigid,  metallic-framed  airship  of  this  type, 
wireless  signals  could  be  transmitted  with  safety  to  a  distance  of  300 
miles  or  more.  All  of  the  later  Zeppelin  airships  which  have  since 
been  wrecked,  particularly  the  passenger-carrying  types,  were 
equipped  with  wireless. 


552 


AERONAUTICAL   PRACTICE  111 

Dangers  from  Electric  Discharge.  While  of  inestimable  advan- 
tage, the  presence  of  the  wireless  apparatus  on  a  metallic  airship 
exposes  it  to  new  dangers,  some  of  which  are  also  present  in  the  case 
of  the  aeroplane.  The  chief  source  of  risk  is  the  large  volume  of 
inflammable  gas  necessary  for  flotation  in  the  case  of  the  huge  diri- 
gibles. In  a  thunder  storm,  a  balloon  is  subject  to  sudden  varia- 
tions of  electric  charge  which  may  produce  sparks  capable  of  ignit- 
ing its  contents.  Wireless  signals  are  accompanied  by  equally  great 
and  rapid  changes  of  potential  which  may  produce  the  same  result. 

It  seems  probable  that  the  destruction  of  the  Zeppelin  airship 
at  Echterdingen  was  due  to  atmospheric  electric  discharges  during 
a  thunder  storm,  while  the  catastrophe  which  befell  the  French  mili- 
tary dirigible  La  Republique  in  September,  1909,  also  appears  to 
have  been  due  indirectly  to  an  electric  spark.  A  hole  was^torn  in 
the  gas  bag  by  the  breaking  of  a  propeller  blade,  which  in  itself  would 
not  have  been  sufficient  to  have  caused  the  sudden  drop  of  300  feet. 
It  is  a  well-known  fact  that  gas  or  steam,  escaping  rapidly  from  an 
orifice,  will  acquire  an  electric  charge  which  may  produce  powerful 
sparks,  and  it  is  thought  that  this  took  place  immediately  follow- 
ing the  rupture  of  the  gas  bag  of  the  Republique,  setting  its  contents 
on  fire. 

As  the  gas  can  not  be  ignited  by  discharges  from  the  envelope 
itself,  the  netting,  ropes,  and  similar  poor  conductors  (unless  they 
become  saturated  with  water),  but  can  be  easily  set  fire  to  by  sparks 
from  the  metal  parts  of  the  valve  and  other  masses  of  metal,  it  is 
obvious  that  all  metlal  and  other  good  conductors  will  have  to  be 
eliminated  from  the  envelope.  There  seems  to  be  no  objection  to 
the  presence  of  metal  in  the  car,  while  a  well-conducting  drag  rope 
is  a  safeguard  against  explosion  in  landing.  If  all  conductors  are 
removed  from  the  vicinity  of  the  gas  bag,  there  would  appear  to  be 
no  danger  in  the  application  of  wireless  telegraphy  to  airships  of  the 
flexible  type.  If  the  same  precautions  be  taken,  dirigibles  of  this 
class  are  no  more  liable  to  ignition  by  atmospheric  electrical  dis- 
charges than  the  free  balloon. 

In  rigid  airships  with  metallic  frames,  the  conditions  are  totally 
different.  It  will  be  apparent  in  the  Zeppelin  type,  with  its  alumi- 
num frame  and  its  numerous  gas  bags  filled  with  hydrogen,  every 
condition  of  easy  ignition  is  present.  Between  the  great  cylindrical 


553 


112  AERONAUTICAL   PRACTICE 

conducting  frame,  which  is  more  than  400  feet  long  and  40  feet  in 
diameter,  and  the  surrounding  air,  there  may  exist  a  difference  of 
potential  of  65,000  volts  when  the  airship  is  horizontal,  and  of  50,000 
volts,  when  steeply  inclined.  A  spark  capable  of  causing  ignition 
may  be  caused  by  a  difference  of  potential  of  only  3,000  volts.  As 
it  does  not  appear  to  be  practicable  to  substitute  wood  for  the  alumi- 
num framing,  Zehnder  recommends  protection  of  the  airship  by  light- 
ning rods  projecting  beyond  the  reach  of  escaping  gas.  He  also 
suggests  making  the  gas  container  of  sheet  metal,  the  stiffness  of 
which  might  make  it  possible  to  employ  a  lighter  skeleton,  thus  keep- 
ing the  weight  within  the  same  limit  as  at  present.  No  electrical 
discharge  could  take  place  within  this  metallic  envelope  and  the 
induced  surface  charge  would  escape  harmlessly  into  the  atmosphere 
from  projecting  seams  and  points.  As  an  additional  precaution, 
the  aluminum  cars  could  be  connected  with  the  aluminum  balloon 
at  several  points  by  a  number  of  wires,  so  that  the  aeronauts  would 
be  enclosed  in  a  sort  of  Faraday's  cage,  protecting  them  from  exter- 
nal electrical  influences. 

Preventive  Methods.  The  experiments  of  Professor  Wiener 
have  not  only  served  to  demonstrate  the  value  of  a  wire  cage  as 
protection  against  electrical  discharges,  but  likewise  have  illustrated 
what  happened  to  a  balloon  when  struck  by  a  spark.  For  this  pur- 
pose, a  model  balloon  was  suspended  above  a  large  induction  coil 
with  the  gaps  of  the  secondary  so  arranged  that  the  largest  diameter 
of  the  balloon  was  between  one  pair,  while  a  second  pair  was  located 
to  discharge  immediately  below  the  valve  opening  of  the  balloon. 
When  a  spark  was  passed  completely  through  a  collodion  balloon, 
rilled  with  either  hydrogen  or  illuminating  gas,  the  gas  ignited  with- 
out explosion  so  that  the  balloon  was  quietly  consumed.  It  is  only 
when  the  balloon  contains  air  mixed  with  gas  that  explosion  takes 
place.  A  balloon  can  even  be  traversed  by  sparks  without  being 
ignited.  Metzeler  has  recently  introduced  a  balloon  material  com- 
posed largely  of  aluminum  for  the  purpose  of  protecting  the  gas  from 
the  sun's  rays,  but  experiments  prove  that  this  material  is  no  better 
conductor  than  the  ordinary  balloon  fabric.  Sparks  can  be  passed 
through  a  balloon  of  Metzeler's  material  without  causing  ignition 
and  even  collodion  balloons  can  transmit  a  few  sparks  without  burn- 
ing. If  the  flow  of  sparks  be  so  rapid  and  dense  as  to  resemble  a 


554 


AERONAUTICAL   PRACTICE  113 

flaming  arc,  it  may  directly  ignite  the  fabric.     Even  if  it  were  pos- 
sible to  make  a  balloon  of  conducting  material,  it  would  still  be 
desirable  to  surround  it  with  a  wire  cage,  as  lightning  naturally  fol- 
lows the  shortest  path.     With  this  provision,  the  conductivity  of 
the  balloon  is  of  no  importance.     Owing  to  its  greater  strength  the 
wire  netting  need  not  be  heavier  than  the  hemp  netting  ordinarily 
employed  on  dirigibles  of  the  flexible  and  semi-flexible  types.     All 
the  experiments  just  referred  to  were  made  with  unprotected  bal- 
loons, but  a  model  surrounded  by  a  wire  cage  allowed  ordinary  sparks 
to  pass  indefinitely,  while  it  also  withstood  a  flaming  arc  for  a  short 
time,    without    igniting — fifteen    seconds   direct   contact  with   the 
flame  was  necessary  to  produce   ignition.     The  ropes  supporting 
the  car  must  also  be  of  wire  and  must  completely  surround  the  car. 
It  might  be  supposed  that  making  the  outside  of  the  balloon  a  good 
conductor  would  rather  invite  danger  from  lightning,  but  this  is  not 
the  case.     Although  the  ordinary  balloon  envelope  is  a  fairly  good 
insulator  against  low  voltages,  it  is  unable  to  resist  the  high  tension 
of  atmospheric  electricity.     An  electroscope  charged  to  2,000  volts 
is  discharged  in  less  than  a  second,  when  it  is  touched  with  a  roll 
of  balloon  fabric  about  six  inches  long.     Hence,  the  balloon  increases 
the  electrical  tension  immediately  above  and  below  it,  as  much  as 
it  would  do  if  it  were  a  perfect  conductor,  but  when  the  discharge 
occurs,  its  destructive  action  will  be  greater  in  proportion  to  the 
electrical  resistance  opposed  to  it.     It  might  also  be  objected  that 
the  Faraday's  cage  would  prove  a  source  of  danger  to  the  occupants. 
The  discharge,  however,  passes  chiefly  through  the  wires,  and  only 
partial  or  inductive  discharges  can  strike  those  in  the  balloon.     It 
is  evident  that  the  Faraday's  cage  is  quite  as  readily  applicable  to  the 
aeroplane  as  it  is  to  the  dirigible,  though  its  use  might  complicate  the 
employment  of  the  aerial  for  wireless  telegraphy,  as  referred  to  later. 
On  the  other  hand,  it  is  quite  possible  that  the  surrounding  net- 
work of  wire  might  be  employed  for  both  purposes  by  suitably  pro- 
tecting the  instruments.     But  even  when  a  balloon  is  thus  pro- 
tected from  lightning,  it  is  exposed  to  another  danger,  atmospheric 
electricity.     A  balloon  has  been  ignited  and  consumed  by  small 
sparks  produced  by  touching  the  escape  valve  after  landing.     This 
valve  and  the  filling  tube,  normally  open  during  flight,  are  the  two 
places  in  which  the  gas  can  come  into  contact  with  the  air  and  there- 


555 


114  AERONAUTICAL  PRACTICE 

fore  need  special  protection.  The  simple  and  long-known  device 
employed  in  the  Davy  safety  miner's  lamp  can  well  be  employed  for 
this  purpose.  These  safety  lamps  are  designed  to  protect  miners 
from  explosions  of  fire  damp,  the  flame  being  surrounded  by  a  fine 
wire  netting  which  conducts  heat  so  well  that  the  temperature 
required  to  ignite  the  gas  can  not  be  produced  on  the  outside.  Any 
gas  which  enters  the  lamp  burns  quietly  without  producing  an  explo- 
sion. Both  the  escape  valve  and  filling  tube  of  the  balloon  could  be 
surrounded  with  a  fine  netting  of  copper  wire,  which  would  also 
afford  protection  from  lightning  in  certain  cases. 

An  electric  discharge  may  be  precipitated  by  pulling  the  valve 
cord  in  a  strong  electric  field,  as,  according  to  Paschen's  experiments, 
the  gap  that  a  certain  tension  will  bridge  is  greater  in  hydrogen  than 
in  air.  This  is  shown  by  connecting  a  Bunsen  burner  with  one 
pipe  of  an  induction  coil  and  gradually  raising  the  other  above  it  until 
the  opening  is  too  great  for  the  sparks  to  bridge.  Upon  turning  on 
the  gas,  the  flow  of  sparks  will  recommence.  If  the  burner  be  sur- 
rounded with  a  wire  netting,  the  gas  will  burn  only  on  the  outside. 
The  experiments  with  the  model  balloons  and  a  large  induction  coil 
showed  that  when  the  sparks  passed  beneath  the  open  filling  tube  of 
the  balloon,  ignition  sometimes  followed,  but  where  protected  by 
a  wire  netting,  a  flaming  arc  playing  upon  the  netting  for  a  minute 
did  not  light  the  gas. 

Wireless  on  the  Zeppelins.  In  regard  to  the  employment  of 
wireless  telegraphy  on  the  Zeppelin  type  of  the  present  form — an 
arrangement  of  the  aerial  which  would  minimize  the  danger  of  igni- 
tion and  would  also  furnish  the  best  electrical  conditions  for  the 
transmission  of  signals  is  suggested;  as  the  hull  of  the  Zeppelin  is 
traversed  by  a  vertical  shaft  or  well,  it  is  possible  to  support  the 
aerial  by  a  simple  Eddy  kite,  which  would  be  kept  aloft  by  the  motion 
of  the  airship.  The  wireless  apparatus,  including  the  dynamo,  would 
be  housed  in  the  middle  of  the  runway  which  connects  the  two  cars. 
The  kite  would  be  connected  with  the  apparatus  by  a  wire  from  600 
to  1,200  feet  in  length,  i.e.,  one-fourth  to  one-fifth  the  length  of  the 
electric  waves  employed.  A  second  wire  of  the  same  length 
and  carrying  a  weight  at  its  end  would  hang  downward  from  the 
apparatus  and  would  be  kept  as  nearly  vertical  as  possible  by  insu- 
lated stay  or  guy  lines  attached  to  the  cars.  The  lower  wire  might, 


556 


AERONAUTICAL   PRACTICE  115 

however,  be  replaced  by  a  fan-shaped  antenna  about  200  feet  long, 
attached  to  the  frame  of  the  airship  and  projecting  .about  30  feet 
below  the  hull.  With  this  arrangement  communication  would  be 
possible  even  when  the  ship  was  flying  low.  Fouling  of  the  propel- 
lers would  have  to  be  guarded  against  by  enclosing  them  in  wire 
baskets  or  housings. 

The  T-shaped  antenna  which  is  carried  by  ships  using  the  Tele- 
funken  system,  could  also  be  applied  without  difficulty  to  the  Zeppe- 
lin airship,  as  the  metal  frame  is  abundantly  able  to  carry  a  light, 
hollow  mast  about  30  feet  high,  which  could  be  raised  and  lowered 
by  ropes.  The  stability  of  the  airship,  however,  would  be  affected 
more  by  this  complicated  device  than  by  the  kite.  Experiments 
have  shown  conclusively  the  great  promise  of  the  use  of  wireless  teleg- 
raphy on  airships,  but  an  indispensable  prerequisite  to  its  adoption 
would  appear  to  be  the  electro-technical  development  of  means  of 
protection  from  all  danger  of  injury  through  the  working  of  the  appa- 
ratus itself,  or  from  atmospheric  electricity. 

WIRELESS  ON  AEROPLANES 

Owing  to  its  far  greater  speed  and  radius  of  action  as  well  as  its 
more  general  availability,  the  employment  of  wireless  telegraphy 
on  the  aeroplane  holds  far  more  promise  for  military  use.  With 
experience  in  taking  observations  from  a  height,  it  will  become  pos- 
sible to  plot  maps,  note  the  character  of  emplacements,  and  the  posi- 
tion of  troops  from  an  altitude  that  would  make  danger  from  shell 
fire  from  below  out  OT  the  question.  To  be  of  any  value,  the  diri- 
gible must  be  so  large  as  to  make  this  impossible. 

First  Message.  To  James  McCurdy,  one  of  the  Curtiss  school 
aviators,  belongs  the  distinction  of  having  been  the  first  to  communi- 
cate by  wireless  from  an  aeroplane  to  a  land  station.  This  was  on 
August  27,  1910,  when  he  sent  the  following  message  from  a  Curtiss 
biplane : 

Over  Barren  Island,  N.  Y.,  6:45  P.  M.,  Aug.  27,  '10. 
To  H.  M.  Horton: 

Another  chapter  in  aerial  achievement  is  recorded  in  the  sending  ef  this 
wireless  message  from  an  aeroplane  in  flight.  McCuRDY. 

Horton  was  the  wireless  operator  on  the  roof  of  the  Sheepshead 
Bay  race-track  grand  stand,  two  or  three  miles  distant  from  Bar- 


557 


116  AERONAUTICAL   PRACTICE 

ren  Island,  though  the  distance  was  probably  less  in  an  airline,  The 
apparatus  was.  an  ingenious  makeshift  merely  intended  for  the  pur- 
pose of  sending  and  was  not  capable  of  receiving  a  message.  It  was 
extremely  compact,  the  complete  outfit,  with  the  exception  of  the 
battery,  being  attached  to  the  steering  wheel  of  the  aeroplane.  The 
battery  was  carried  in  the  aviator's  vest  pocket,  while  the  aerial 
consisted  of  50  feet  of  ordinary  wire  held  straight  by  a  small  lead 
weight,  the  whole  trailing  after  the  machine  in  flight.  Such  an  out- 
fit naturally  had  but  a  very  limited  range,  probably  not  more  than  five 
miles,  owing  to  the  small  amount  of  energy  available,  and  would  be 
subject  to  destructive  interference  from  the  waves  sent  out  by  more 
powerful  stations  in  its  vicinity.  It  was  intended  only  to  demon- 
strate the  possibility  of  communicating  with  an  aeroplane  in  flight. 

Owing  to  the  high  speed  at  which  an  aeronautic  motor  runs,  how- 
ever, it  would  be  practical  to  carry  a  very  compact  alternating  gener- 
ator which  would  weigh  very  little  and  still  give  the  aeroplane  send- 
ing station  a  comparatively  wide  radius  of  action — doubtless  up  to 
100  miles  or  more,  due  to  the  greater  facility  with  which  the  electro- 
magnetic waves  can  be  transmitted  from  a  height.  The  remainder 
of  the  apparatus  could  likewise  be  made  in  very  compact  and  durable 
form,  so  that  there  would  appear  to  be  no  " wireless  problem"  where 
the  aeroplane  is  concerned — it  is  merely  a  matter  of  designing  instru- 
ments for  the  purpose. 

Morton's  Experiments.  The  question  of  equipping  the  aero- 
plane with  a  suitable  aerial  that  would  be  effective  without  being  an 
encumbrance,  as  well  as  the  fact  that  a  very  substantial  percentage 
of  the  energy  emitted  by  the  sending  apparatus  was  absorbed  by 
the  numerous  guy  wires  which  also  acted  as  a  shield  to  the  antennas, 
appeared  to  present  a  difficult  obstacle  at  first.  Both,  however,  have 
been  overcome  by  a  very  simple  expedient,  that  of  employing  the 
guy  wires  themselves  as  the  antennas.  After  experimenting  for  a 
long  while  with  numerous  different  methods  of  stringing  separate 
antennas,  H.  M.  Horton  hit  upon  the  idea  of  using  the  wires  for 
this  purpose,  while  the  motor  is  utilized  as  a  ground.  Experiments 
which  were  made  with  a  machine  thus  equipped  and  located  in  the 
building  of  the  United  States  Aeronautical  Reserve  in  New  York 
City  proved  most  successful.  Messages  were  received  from  vari- 
ous stations  throughout  the  city  and  even  from  ships  at  sea,  despite 


558 


AEEONAUTICAL   PRACTICE 


117 


the  fact  that  the  aeroplane  was  located  on  the  first  floor  of  the  build- 
ing and  was  not  connected  with  any  form  of  antenna  protruding 
above  the  roof.  A  very  light  equipment  was  used,  the  total  weight 
not  exceeding  65  pounds,  although  a  6-inch  spark  coil  was  employed. 
Energy  was  derived  from  a  12-volt  storage  battery  with  a  50-ampere- 
hour  capacity,  the  six  cells  weighing  but  40  pounds.  The  guy  wires 
were  connected  in  series  and  gave  a  total  length  of  800  feet  on  the 
machine  in  question.  However,  the  employment  of  a  storage  bat- 
tery in  this  connection  can  be  considered  only  as  a  temporary  expe- 
dient in  view  of  the  obvious  limitations  of  such  a  source  of  energy. 


Fig.  54.     Parmalee  and  Lieutenant  Beck  in  a  Wright  Biplane,  Operating 
a  Wireless  Outfit 

For  extended  practical  use,  a  generator  would  be  necessary.  As 
the  required  power  is  right  at  hand,  this  could  take  the  form  of 
a  small  high-frequency  alternator,  and  as  this  could  be  wound  for  a 
high  voltage,  the  weight  of  the  transformer  necessary  could  be  cor- 
respondingly reduced. 

Recent  Records.  Lorraine.  Numerous  other  experimenters 
have  been  at  work  with  wireless  during  the  past  year  or  so,  Robert 
Lorraine,  in  England,  having  succeeded  in  maintaining  perfect 
communication  from  his  aeroplane  with  a  land  station  more  than 
a  mile  distant. 


559 


118  AERONAUTICAL   PRACTICE 

Beck.  The  most  practical  results,  however,  were  those  of  the 
trials  carried  out  during  the  course  of  the  aviation  meet  at  San 
Francisco  in  January,  1911.  Lieutenant  Paul  W.  Beck  of  the  United 
States  Signal  Corps  went  aloft  in  a  Wright  biplane  piloted  by  Parm- 
alee,  Fig.  54,  and  transmitted  wireless  messages  for  a  considerable 
distance  while  at  a  height  of  1,000  feet.  These  messages  were 
received  at  the  Mare  Island  Navy  Yard,  40  miles  away,  as  well  as 
at  the  Yerba  Buena  Island  training  school  in  San  Francisco  Bay. 
In  Lieutenant  Beck's  experiments  a  100-foot  length  of  copper  wire 
was  trailed  along  behind  the  aeroplane.  In  France,  wireless  mes- 
sages have  been  successfully  transmitted  15  miles  from  an  aero- 
plane; while  in  England,  during  a  trip  of  the  military  dirigible  Beta, 
communication  was  established  with  headquarters  30  miles  distant. 

McCurdy.  During  the  Bridgeport,  Connecticut,  Aviation  Meet 
in  May,  1911,  McCurdy  set  a  new  long-distance  mark  in  wireless 
communication  from  an  aeroplane  by  sending  messages  to  the  opera- 
tor in  the  dome  of  the  World  Building  in  New  York  City,  55  miles 
distant,  while  a  number  of  other  stations  within  a  shorter  radius 
also  picked  up  his  messages.  The  apparatus  was  constructed  for 
the  New  York  World  in  three  days  by  Oscar  Roesen,  an  electrical 
engineering  student  at  Stevens,  and  was  probably  the  first  set  capable 
of  both  sending  and  receiving  that  has  been  mounted  on  an  aero- 
plane. The  transmitter  consisted  of  a  4-inch  induction  coil  of  the 
ordinary  vibrating  type,  supplied  with  current  by  15  dry  cells  con- 
nected in  series,  thus  giving  a  voltage  of  22.5,  while  the  amperage 
was  high.  The  helix  was  a  wood  frame  5  inches  in  diameter  and 
wound  with  12  turns  of  No.  6  B  &  S  gauge  aluminum  wire,  while  the 
condenser  consisted  of  copper  plates  with  a  special  insulating  material 
as  the  dielectric.  An  ordinary  telegraph  key  was  employed.  The 
receiver  comprised  a  mineral  detector,  two  straight  tuning  coils,  and 
a  pair  of  2,000-ohm  head  phones.  The  aerial  consisted  of  a  series 
of  wire  strung  forward  from  the  tail  on  either  side  to  points  directly 
above  the  ailerons  at  the  ends  of  the  upper  plane  of  the  Curtiss 
machine,  Fig.  55.  For  a  ground,  or  rather  for  a  balancing  aerial, 
the  motor  supplemented  by  wires  carried  out  in  either  direction 
to  the  ends  of  the  main  plane  was  employed.  The  apparatus 
proper  was  mounted  in  a  small  box  carried  below  the  aviator  on  the 
skids  of  the  machine,  while  the  sending  key  was  placed  on  the  steer- 


560 


AERONAUTICAL   PRACTICE 


119 


ing  wheel.    The  arrangement  is  plainly  illustrated  by  the  accompany- 
ing sketch,  Fig.  56.     A  is  the  box,  B  the  key,  dotted  lines  C  the 


Fig.  55.     Diagram  Showing  Method  of  Making  an  Aerial  on  a  Biplane 

ground  or  balancing  aerial,  and  full  lines  CC  the  aerial  proper,  the 
smaller  sketch  below  showing  how  this  was  wired  up.  The  weight 
of  the  complete  outfit  was  between  40  and  50  pounds.  Lieutenant 
Fickel,  U.  S.  A.,  detailed  by  the  War  Department  to  attend  the 
meet,  was  very  much  impressed  with  the  set  and  sent  a  complete 
description  of  it  to  the  Signal  Corps  at  Washington.  Experiments 


Fig.  56.     Diagram  Showing  Location  of  Circuits  and  Equipment  of  a 
Wireless  Outfit 


were  first  made  on  a  Saturday  and  while  McCurdy's  signals  were 
plainly  heard  at  the  temporary  receiving  station  on  the  field,  the 


561 


120  AERONAUTICAL   PRACTICE 

interference  of  numerous  adjacent  stations  made  it  impossible  for 
the  operator  in  New  York  to  pick  them  up.  On  the  following  day 
there  was  an  absence  of  interference,  and  the  messages  were  plainly 
heard  in  New  York  on  three  different  trials,  thus  establishing  a  new 
distance  record  for  aeroplane  work,  and  this  is  of  even  greater  impor- 
tance in  having  reached  the  heart  of  the  metropolis,  as  New  York 
City  is  generally  conceded  to  have  many  adverse  elements  for  suc- 
cessful wireless  reception  from  outside  points,  chiefly  due  to  the 
great  number  of  high,  steel-frame  buildings.  Tests  made  of  the 
receiving  abilities  of  the  set  showed  it  to  be  capable  of  picking  up 
messages  from  a  distance  of  200  miles,  but  unfortunately  no  trials 
of  this  nature  were  carried  out  in  the  air. 

General  Problems.  It  will  be  apparent  from  the  foregoing 
that  all  of  the  experiments  made  thus  far  have  been  in  transmitting 
messages  from  an  aeroplane  in  flight,  and  while  this  is  a  very  val- 
uable accomplishment,  receiving  is  quite  as  necessary,  to  take  com- 
plete advantage  of  the  value  of  the  wireless  as  a  means  of  communica- 
tion, and  for  reasons  that  are  obvious  this  does  present  more  of  a 
problem  than  the  mere  sending  of  messages. 

Eliminating  Noise.  The  chief  difficulty  is  that  of  noise,  as 
with  the  unmuffled  motors  now  generally  in  use,  it  is  practically 
impossible  for  two  men  sitting  side  by  side  in  an  aeroplane  to  carry 
on  a  conversation.  This  is  further  complicated  by  the  rush  of  the 
wind  and  the  high  pitched  note  occasioned  by  the  vibration  of  the 
numerous  guy  wires  and  struts,  but  with  close-fitting,  double-head 
receivers,  there  should  be  no  difficulty  in  shutting  out  practically 
everything  but  the  noise  of  the  motor.  The  matter  of  expediency 
that  has  been  responsible  for  the  adoption  of  so  many  of  the  make- 
shift features  of  design  that  characterize  the  present-day  aeroplane, 
and  probably  will  continue  at  least  for  a  few  years  to  come,  has 
likewise  been  responsible  for  the  elimination  of  the  muffler  on 
the  motor.  But  even  now,  design  and  construction  have  advanced 
to  a  point  where  there  is  really  no  necessity  for  longer  doing  without 
this  essential,  as  both  the  muffler  and  its  connecting  pipe  can  readily 
be  made  of  aluminum,  though,  for  that  matter,  the  weight  of  the 
standard  type  as  employed  on  the  automobile  would  not  form  any 
very  serious  drawback.  Considerably  more  difficulty  would  be 
encountered  in  muffling  motors  of  the  rotary  type,  but  they,  need 


562 


AERONAUTICAL   PRACTICE  121 

it  least,  as  the  explosions  of  a  seven-  or  fourteen-cylinder  Gnome 
motor  running  at  full  speed  overlap  to  a  degree  that  converts  the 
exhaust  into  a  loud  buzz,  rather  than  the  disagreeable  and  ear- 
cracking  rapid-fire  bang  of  the  four-  or  six-cylinder  vertical  motor. 

Use  of  Visible  Signals.  Should  the  usual  audible  method  of 
receiving  not  prove  practical,  two  alternatives  are  open,  both  involv- 
ing the  use  of  a  visible  signal.  In  one,  a  coherer  could  be  connected 
with  a  tuning  condenser  shunted  across  it,  the  former  being  auto- 
matically decohered  every  two  seconds  by  a  striker  actuated  by  a 
magnet  excited  by  a  clockwork  contact  maker.  A  relay  and  bat- 
tery are  connected  in  series  with  the  coherer,  and  the  local  circuit 
of  the  relay  is  connected  with  another  battery  and  small  incandes- 
cent lamp.  Each  time  a  signal  is  received  the  lamp  would  light — 
one  second  for  a  dot  and  two  seconds  for  a  dash.  These  long  signals 
are  obviously  necessary,  but  in  spite  of  that  a  message  could  be 
received  with  reasonable  rapidity.  The  second  alternative  is  that 
of  employing  an  inker,  this  method  also  involving  the  use  of  a  coherer. 
The  inking  apparatus,  however,  is  not  only  comparatively  heavy, 
but  in  order  to  work  satisfactorily,  requires  fairly  close  adjustment, 
so  thitt  it  would  not  be  suitable  for  use  where  there  is  much  vibration 
— the  question  of  vibration  is  probably  the  most  serious  element  of 
the  problem.  The  coherer  is  not  a  particularly  sensitive  receiver  of 
the  weak  impulses  which  have  to  be  caught,  and  has  long  since  been 
practically  abandoned  in  wireless  practice.  But  even  if  it  were  suf- 
ficiently sensitive  for  such  use,  it  would  probably  be  impossible  to 
make  the  coherer  .work  long  enough  to  start  the  local  side  of  the 
relay  working  effectively,  particularly  if  the  mechanical  decohe- 
sion  had  to  be  rapid.  In  fact,  the  actual  number  of  impulses  per 
second  of  a  four-cylinder,  two-cycle  engine,  or  a  six-cylinder,  four- 
cycle, or  any  of  the  rotary  motors,  is  too  great  to  permit  a  coherer 
to  act,  while  a  coherer  insensitive  to  the  abruptness  of  the  shock 
would  not  be  sensitive  enough  to  respond  to  the  wireless  impulses. 
Either  the  mineral  or  the  electrolytic  type  of  detector  is  far  more 
sensitive,  but  as  its  adjustment  must  be  delicate  to  work  effectively, 
it  would  also  be  placed  at  a  serious  disadvantage  by  the  vibration. 

Forms  of  Aerial.  The  question  of  the  most  practical  form  of 
aerial  to  employ  is  another  difficulty  that  affects  both  sending  and 
receiving.  The  use  of  a  long  trailing  wire,  as  well  as  the  employ- 


563 


122  AERONAUTICAL   PRACTICE 

ment  of  the  network  of  guys  and  braces,  has  already  been  referred 
to  in  connection  with  experiments  carried  out  by  McCurdy  and 
American  army  officers.  Trailing  wires  present  so  many  sources  of 
danger  to  a  machine  traveling  at  high  speed,  that  few  pilots  would 
care  to  consent  to  their  use,  while  connecting  up  the  bracing  of  the 
aeroplane  is  equally  impracticable  as  every^  piece  of  metal  on  the 
machine  then  becomes  charged,  and  in  sending,  serious  shocks  might 
be  received  by  the  pilot  or  his  passenger.  Farman  has  employed 
two  trailing  wires,  each*  about  400  feet  long,  and  Baker  has  adapted 
a  similar  arrangement  to  a  Bristol  biplane  in  England,  the  wires, 
however,  not  being  allowed  to  hang  loose  in  the  latter  case,  thus  lim- 
iting their  capacity.  Instead  of  using  balanced  aerials,  as  in  the 
McCurdy  experiments  described  above,  he  coupled  them  to  each  end 
of  an  inductance  coil,  thus  increasing  their  effective  length  to  the 
greatest  extent  possible  without  sacrificing  their  efficiency.  The 
apparatus  consisted  of  a  6-inch  induction  coil  with  a  f-inch  spark 
gap  located  as  far  away  from  the  gasoline  tank  as  possible.  Two 
light  brass  rods  extended  from  the  coil  well  into  the  space  between 
the  two  main  planes  of  the  machine  and  to  one  side  of  the  tank,  and 
two  f-inch  rods  sliding  on  these  and  with  their  ends  separated  by 
f  inch,  formed  the  spark  gap  terminals.  Shunted  across  the  spark 
gap  was  a  condenser  of  the  Leyden  jar  type,  and  an  inductance  coil 
consisting  of  seven  turns  of  No.  14  copper  wire  wound  on  a  light 
ebonite  drum.  This  inductance  had  sliding  contacts  so  that  the 
number  of  turns  used  could  be  varied  in  the  usual  manner,  in  order 
to  tune  the  two  circuits.  The  two  aerial  wires  were  connected  to  the 
two  ends  of  the  inductance  in  use  and  the  aerial  circuit  was  brought 
into  tune  with  the  shunt  circuit.  A  storage  battery  of  five  cells 
supplied  the  necessary  energy,  about  50  to  60  watts  being  required. 
Two  new  arrangements  which  should  greatly  increase  the  efficiency 
of  the  apparatus  have  since  been  adopted.  The  more  important  of 
these  is  a  long,  light  brass  tube  attached  to  the  tail  of  the  aeroplane 
but  insulated  from  it.  This  acts  as  counter-capacity  or  "ground" 
to  a  long  aerial  wire  on  the  other  side.  This  aerial  starts  from  the 
nose  of  the  machine,  and  is  carried  thence  to  the  extreme  outer  edge 
of  the  main  plane,  back  to  the  tail,  and  from  this  to  a  loose  connec- 
tion, 60  feet  of  copper  wire  trailing  behind. 

Possible  Developments.    It  is  evident  that  these  isolated  experi- 


564 


AERONAUTICAL   PRACTICE  123 

ments,  while  more  or  less  numerous,  are  but  the  beginning  of  the 
serious  study  that  will  be  given  the  matter  within  the  next  year  or 
so.  Nine- hour,  non-stop  flights  covering  more  than  400  miles  give 
some  idea  of  what  will  be  accomplished  in  the  way  of  long-distance 
flying  in  the  near  future — in  fact,  they  make  the  possibility  of  being 
able  to  cover  more  than  1,000  miles  per  day  of  twenty-four  hours 
seem  very  close  at  hand,  so  that  Atwood's  proposal  to  fly  across  the 
Atlantic  in  three  days  appears  to  be  only  a  question  of  carrying  suf- 
ficient fuel.  To  be  able  to  keep  in  constant  communication  with 
these  long-distance  flyers  would  be  invaluable,  and  that  is  what 
experimenters  in  the  wireless  field  aim  to  accomplish. 

Wireless  telegraphy  from  the  dirigible  has  already  reached  a 
more  advanced  stage,  as  neither  the  use  of  a  trailing  wire  nor  the 
matter  of  weight  present  such  serious  disadvantages  as  on  the  aero- 
plane. The  apparatus  used  on  the  British  military  dirigible  Beta 
weighed  approximately  100  pounds,  and  as  signals  have  been  sent 
50  miles  under  favorable  conditions,  the  proportion  of  weight  to 
distance  of  transmission  was,  roughly  speaking,  2  pounds.  But  an 
ordinary  induction  coil  and  accumulator  were  employed,  so  that 
this  can  scarcely  be  taken  as  a  criterion.  They  were  used  in  con- 
nection with  a  trailing  aerial  and  a  counter-capacity,  and,  as  the 
chief  requirement  of  the  latter  is  superficial  area  to  take  the  charge, 
as  light  a  substance  as  possible,  such  as  paper-thin  sheet  aluminum, 
could  be  employed. 

The  form  of  the  wireless  installation  suggested  by  one  of  the 
chief  English  experimenters  as  best  adapted  to  the  needs  of  the  air- 
ship is  that  of  a  small  auxiliary  motor,  say,  a  two-cylinder,  3-  to  4- 
horse-power  machine,  directly  coupled  to  an  alternating  generator 
of  about  2  kilowatts  capacity,  together  with  an  aerial  about  350  feet 
long,  and  a  counter-capacity  in  the  form  of  very  thin  metallic  sheet- 
ing, suitably  disposed.  Considerable  attention  is  now  being  given 
to  the  production  of  portable  apparatus.  The  chief  limiting  factor 
in  connection  with  small  receivers  naturally  has  to  do  with  the 
detector,  the  vacuum  valve  type  of  Professor  J.  A.  Fleming  probably 
being  the  most  suitable  in  many  respects,  and  next  to  that  an 
electrolytic  detector. 

Akron  Outfit.  The  new  dirigible  Akron,  in  which  Melvin  Vani- 
man  is  to  make  his  second  attempt  at  crossing  the  Atlantic,  is  a 


565 


124  AERONAUTICAL   PRACTICE 

forcible  example  of  the  careful  attention  now  being  given  to  wireless 
equipment  and  the  dependence  placed  upon  it  as  a  safeguard.  Van- 
iman,  it  will  be  recalled,  was  Wellman's  chief  engineer  on  the  Amer- 
ica, and  he  has  taken  advantage  of  that  experience  to  embody  all 
the  improvements  in  the  new  equipment  that  were  found  lacking 
in  the  America's  set.  The  latter  had  a  sending  range  of  only 
80  to  90  miles,  so  that  while  the  operator  could  catch  the  numerous 
inquiries  that  filled  the  air  regarding  the  America's  whereabouts 
during  the  48  hours  or  more  that  it  was  out  of  sending  range,  he  could 
not  reply  to  any  of  them.  The  equipment  of  the  Akron  is  a  Mar- 
coni set  with  a  sending  range  of  700  to  800  miles  and  consists  of  a 
3-kilowatt,  120-cycle,  alternating-current  generator,  direct  driven 
by  a  17-horse-power,  4-cylinder  gasoline  engine.  For  receiving, 
the  most  advanced  type  of  musical,  rotary  spark  gap  and  a  valve 
detector  will  be  employed.  As  a  counter-capacity  does  not  permit 
of  the  most  efficient  operation,  a  flexible,  phosphor  bronze  wire 
trailing  in  the  water  will  constitute  the  ground,  the  equilibrator 
which  was  used  for  that  purpose  on  the  America  having  been  aban- 
doned. This  trailing  ground  is  wound  on  a  drum  and  sufficient  wire 
is  provided  to  reach  the  water  at  any  point  from  100  to  1,200  feet 
elevation,  the  amount  played  out  depending  upon  the  height  at 
which  the  airship  is  flying.  However,  should  the  airship  rise  higher, 
provision  has  been  made  to  operate  the  equipment  as  an  unbalanced 
Hertz  oscillator  without  a  ground.  The  transmitter  is  of  the  loose- 
coupled  type  and  is  so  arranged  that  considerable  variation  in  the 
natural  period  of  the  open  oscillating  circuit  will  have  a  minimum 
effect  upon  the  transmitted  signals.  The  frame  of  the  envelope  is 
used  as  one  side  of  the  oscillator,  the  trailing  ground  acting  as  the 
other.  Particular  care  has  been  taken  in  the  design  of  the  various 
parts  of  the  apparatus  to  prevent  any  possibility  of  a  spark  from 
the  high-tension  apparatus  igniting  the  hydrogen  gas.  Jack  Irwin, 
whose  call  of  distress  from  the  America  brought  the  S.  S.  Trent 
to  their  rescue,  will  accompany  the  Akron  as  operator. 


566 


SI 

i 


II 
3* 


84 


BUILDING  AND  FLYING  AN 
AEROPLANE 

PART  I 


One  of  the  commonest  phases  of  interest  in  aviation  is  the 
desire  to  build  a  flying  machine.  In  fact,  this  is  very  frequently 
the  first  thing  the  experimenter  undertakes  after  having  gone  into 
the  theory  of  flight  to  some  extent.  Only  too  often,  no  effort  what- 
ever is  made  to  get  beyond  theory  and  the  machine  is  an  experiment 
in  every  sense  of  the  word.  An  experience  of  this  nature  is  costly 
—far  more  so  than  is  agreeable  for  the  student,  and  is  likely  to 
result  in  disgusting  him  with  aviation  generally.  There  are  hundreds 
of  schemes  and  principles  in  the  art  that  have  been  tried  again  and 
again  with  the  same  dismal  failure  in  the  end.  Refer  to  the  story 
of  the  Wright  Brothers  and  note  how  many  things  they  mention 
having  tried  and  rejected  as  worse  than  useless.  About  once  in  so 
often  someone  "rediscovers"  some  of  these  things  and,  having  no 
facilities  for  properly  investigating  what  patent  attorneys  term  the 
"prior  art"  (everything  that  has  gone  before,  from  the  beginning  of 
invention,  or  at  least  patented  invention)  becomes  possessed  of 
the  idea  that  he  has  hit  upon  something  entirely  novel  and  wholly 
original.  There  is  no  desire  in  the  present  work  to  discourage  the 
seeker  after  new  principles — undoubtedly  there  are  many  yet  to  be 
discovered.  The  art  of  flight  is  in  its  infancy  and  there  is  still  a 
great  deal  to  be  learned  about  it,  but  there  is  no  more  discouraged 
inventor  than  he  who  discovers  a  principle  and,  after  having  experi- 
mented with  it  at  great  expense,  finds  that  it  is  only  one  of  many 
things  that  numerous  others  have  spent  considerable  money  in 
proving  fallacious,  a  great  many  years  ago. 

If  it  be  your  ambition  to  build  a  flying  machine  and  you  believe 
that  you  have  discovered  something  new  of  value,  it  will  be  to  your 
interest  to  retain  a  responsible  patent  attorney  to  advise  you  as  to 
the  prior  art,  before  expending  any  money  on  its  construction.  You 
will  find  it  very  much  more  economical  in  the  end.  There  are  prob- 

Copyright,  1912,  by  American  School  of  Correspondence. 


567 


2  BUILDING  AND  FLYING  AN  AEROPLANE 

ably  not  more  than  half  a  dozen  men  alive  in  this  country  today 
who  "know  all  the  schemes  that  won't  work."  The  average  seeker 
after  knowledge  is  assuredly  not  likely  to  be  one  of  these  few,  so 
that  until  he  knows  he  is  working  along  new  and  untried  lines  that 
give  promise  of  success,  it  will  pay  him  to  stick  to  those  that  have 
proved  successful  in  actual  practice.  In  other  words,  to  confine 
his  efforts  in  the  building  line  to  a  machine  that  experience  has 
demonstrated  will  fly  if  properly  constructed  and,  what  is  of  equal 
importance,  skilfully  handled.  Build  a  machine,  by  all  means,  if 
you  have  the  opportunity.  It  represents  the  best  possible  experience. 
But  as  is  pointed  out  under  the  "Art  of  Flying,"  take  a  few  lessons 
from  some  one  who  knows  how  to  fly,  before  risking  your  neck  in 
what  is  to  you  a  totally  untried  element.  Even  properly  designed 
and  constructed  machines  are  not  always  ready  to  fly.  An  aeroplane 
needs  careful  inspection  of  every  part  and  adjustment  before  it  is 
safe  to  take  to  the  air  in  it,  and  to  be  of  any  value  this  looking- 
over  must  be  carried  out  by  an  experienced  eye. 

BUILDING  AEROPLANE  MODELS 

The  student  may  enter  upon  the  business  of  building  to  any 
extent  that  his  inclination  or  his  financial  resources  or  his  desire  to 
experiment  may  lead  him.  The  simplest  stage,  of  course,  is  that 
of  model  building  and  there  is  a  great  deal  to  be  learned  from  the 
construction  and  flying  of  experimental  models.  This  has  become 
quite  a  popular  pastime  in  the  public  schools  and  some  very  credit- 
able examples  of  work  have  been  turned  out.  The  apparent  limita- 
tions of  these  rubber-band  driven  models  need  not  discourage  the 
student,  as  some  of  the  school-boy  builders  have  succeeded  in  con- 
structing models  capable  of  flying  a  quarter  mile  in  still  air  and  their 
action  in  the  air  is  wonderfully  like  the  full-sized  machines. 

Models  with  Rubber=Band  Motor.  The  limitations  of  the 
available  power  at  command  must  be  borne  in  mind,  as  the  rubber- 
band  motor  is  at  best  but  a  poor  power  plant.  It  is  accordingly  not 
good  practice  to  have  the  spread  of  the  main  planes  exceed  24  inches, 
though  larger  successful  models  have  been  built.  In  attempting  to 
reproduce  any  of  the  well-known  models,  difficulty  is  often  experi- 
enced in  accommodating  the  rubber-band  motor  to  them,  as  even 
where  the  necessary  space  is  available,  its  weight  throws  the  balance 


568 


BUILDING  AND  FLYING  AN  AEROPLANE  3 

out  entirely,  and  the  result  is  a  model  that  will  not  fly.  This  has  led 
to  the  production  of  many  original  creations,  but  these,  while  excel- 
lent flyers,  would  not  serve  as  models  for  larger  machines,  as  of  neces- 
sity they  have  been  designed  around  their  power  plants.  The  rubber 
bands  for  this  purpose  may  be  purchased  of  any  aeronautic  supply 
house.  The  most  practical  method  of  mounting  the  motor  is  to 
attach  it  to  the  rear  end  of  the  fuselage,  usually  a  single  stick,  which 
is  accordingly  made  extra  long  for  that  purpose.  At  the  other  end 
it  is  attached  to  a  bent  wire  fastened  to  the  propeller  in  order  to 
revolve  the  latter.  An  easy  way  to  wind  up  the  motor  is  to  employ 
an  ordinary  egg  beater,  modified  as  described  below,  or  a  hand 


Fig.  1.     Details  of  ^Jain  Frame  of  Rubber-Band  Driven  Aeroplane  Model 

drill,  inserting  a  small  wire  yoke  in  the  jaws  in  place  of  the  usual 
drill,  or  bit.  This  yoke  is  placed  so  as  to  engage  the  propeller  blades, 
and  the  latter  is  tl^en  turned  in  the  opposite  direction,  storing 
energy  in  the  rubber  band  by  twisting  its  strands  tightly. 

For  those  students  who  do  not  care  to  undertake  an  original 
design  at  the  outset,  or  who  would  prefer  to  have  the  experience 
gained  by  building  from  a  plan  that  has  already  been  tried,  before 
attempting  to  originate,  the  following  description  of  a  successful 
model  is  given.  This  model  can  not  only  be  made  for  less  than  the 
models  sold  at  three  to  five  dollars,  but  is  a  much  more  efficient  flyer, 
having  frequently  flown  700  feet. 

Main  Frame.  The  main  frame  of  the  model  monoplane  con- 
sists of  two  strips  A  of  spruce,  each  28  inches  long,  and  measuring  in 
cross  section  J  by  f  of  an  inch.  As  shown  in  Fig.  1,  the  two  strips 
are  tied  together  at  the  front  with  strong  thread  and  are  then 


569 


Fig.  2. 


Details  of  Forward  Skids  of 
Aeroplane  Model 


a  pitch   of   about    10   inches. 


4  BUILDING  AND  FLYING  AN  AEROPLANE 

glued,  the  glue  being  spread  over  and  between  the  windings  of  the 
thread,  Figs.  1  and  2.  The  rear  ends  of  these  strips  are  spread 
apart  4J  inches  to  form  a  stout  triangular  frame,  and  are  tied  together 

by  cross  bars  of  bamboo  B  and 
C  which  are  secured  to  the  main 
strips  A  by  strong  thread  and 
glue. 

Propellers.  The  propellers  D  are 
two  in  number  and  are  carried  by 
the  two  long  strips  A.  Each  pro- 
peller is  5  inches  in  diameter,  and 
is  whittled  out  of  a  single  block  of 
white  pine.  The  propellers  have 
After  the  whittling  is  done  they 
are  sandpapered  and  coated  with  varnish.  The  thickness  of  the 
wood  at  the  hub  E2,  Fig.  3,  of  the  propeller  should  be  about  f 
inch.  At  the  rear  ends  of  the  strips  A,  bearing  blocks  El  are  secured. 
These  bearing  blocks  are  simply  small  pieces  of  wood  projecting 
about  f  inch  laterally  from  the  strips  A.  They  are  drilled  to 
receive  a  small  metal  tube  T2  (steel,  brass,  or  copper),  through  which 
tube  the  propeller  shaft  Tl  passes. 

The  propeller  shaft  itself  consists  of  a  piece  of  steel  wire  passing 
through  the  propeller  hub  and  bent  over  the  wood,  so  that  it  can 
not  turn  independently  of  the  propeller.  Any  other  expedient  for 
causing  the  propeller  to  turn  with  the  shaft  may  obviously  be 

employed.  Small  metal  washers 
773,  at  least  three  in  number,  are 
slipped  over  the  propeller  shaft 
so  as  to  lie  betwreen  the  propeller 
and  the  bearing  block. 

That  portion  of  the  propeller 
shaft  wilich  projects  forwardly 
through  the  bearing  block  El  is 
bent  to  form  a  hook  T4.  To  the  hook  T1  rubber  strips  T,  by  which 
the  propellers  are  driven,  are  secured.  The  rubber  strips  are  nearly 
as  long  as  the  main  strips  A.  At  their  forward  ends  they  are  secured 
to  a  fastening  consisting  of  a  double  hook  GH,  the  hook  G  lying  in 
a  horizontal  plane,  the  hook  H  in  a  vertical  plane.  The  hook  G  holds 


Fig.  3.      Details  of  Propeller  and  Rudder 
of  Aeroplane  Model 


570 


BUILDING  AND  FLYING  AN  AEROPLANE  5 

the  rubber  strips,  as  shown  in  Figs.  1  and  4,  while  the  hook  H  en- 
gages a  hook  T.  This  hook  is  easily  made  by  passing  a  strip  of  steel 
wire  through  the  meeting  ends  of  the  main  strips  A,  the  portions 
projecting  from  each  side  of  the  strips  being  bent  into  the  hooks  I. 
Skids.  Three  skids  are  provided,  on  which  the  model  slides, 
one  at  the  forward  end,  and  two  near  the  rear  end.  All  are  made 
of  bamboo.  As  shown  in  Fig.  2  the  front  skid  may  be  of  any  length 
that  seems  desirable.  A  6-inch  piece  of  bamboo  will  probably  answer 
most  requirements.  This  piece  N  is  bent  in  opposite  directions  at 
the  ends  to  form  arms  Z  and  U.  The  arm  Z  is  secured  to  the  forward 
ends  of  the  two  strips  A,  constituting  the  main  frame,  by  means  of 
thread  and  glue.  The  strips  and  skid  are  not  held  together  by  the 
same  thread,  but  the  skid  is  attached  to  the  two  strips  after  they  have 


P'ig.  4.      Details  of  Rear  Skids  on  Aeroplane  Model 

been  wound.  Hence,  there  are  two  sets  of  windings  of  thread,  one 
for  the  two  strips  A  themselves,  and  another  for  the  skid  and  the 
strips.  Strong  thread  and  glue  should  be  used,  as  before.  In  order 
to  stiffen  the  skid,  two  bamboo  struts  W  will  be  found  necessary. 
These  are  bent  over  at  the  ends  to  form  arms  V ^  Fig.  2.  Each  of  the 
arms  is  secured  to  the  under  side  of  a  strip  A  by  strong  thread  and 
glue.  The  arms  X  are  superimposed  and  tied  to  the  bamboo  skid  V 
with  strong  thread  and  glue. 

The  two  rear  skids,  of  which  one  is  shown  in  Fig.  5,  consist  each 
of  two  5-inch  strips  of  bamboo  S,  likewise  bent  at  either  end  in  opposite 
directions  to  form  arms  S2  and  S3.  The  arms  S2  are  fastened  to  the 
strips  A  by  strong  thread  and  glue.  To  stiffen  the  skids  a  strut  Ci  is 
provided  for  each  skid.  Each  strut  consists  of  a  3-inch  strip  of 
bamboo  bent  over  so  as  to  form  arms  C2.  Strong  thread  and 
glue  are  employed  to  fasten  each  strut  in  position  on  the  strip  and 


571 


6 


BUILDING  AND  FLYING  AN  AEROPLANE 


the  skid.  In  the  crotch  of  the  triangular  space  Blf  a  tie  bar  J,  Figs. 
4  and  5,  is  secured  by  means  of  thread  and  glue.  This  tie  bar  con- 
nects the  two  skids,  as  shown  in  Figs.  1  and  4,  and  serves  to  stiffen 

them.     The  triangular  space  B^ 

^         j^k —  -   -  -M\>        ^  /   ^     is  covered  with  paper,  preferably 

bamboo  paper.  If  bamboo  paper 
is  not  available,  parchment  or 
stiff  light  paper  of  some  kind 
may  be  used.  It  does  not  need  to 
be  waterproof.  Thus  triangular 
fins  are  formed  which  act  as 


Fig. 


Enlarged  Details  of  One  Rear 
Skid,  Aeroplane  Model 


stabilizing  surfaces. 
Main  Planes.  The  main  planes  are  two  in  number,  but  are 
different  in  size.  Contrary  to  the  practice  followed  in  large  man- 
carrying  monoplanes,  the  front  supporting  surface  is  comparatively 
small  in  area  and  the  rear  supporting  surface  comparatively  large. 
These  supporting  surfaces  L  and  P  are  shown  in  detail  in  Figs.  6 
and  7.  It  has  been  found  that  a  surface  of  considerable  area  is 
required  at  the  rear  of  the  machine  to  support  it,  hence,  the  dis- 
crepancy in  size.  Although  the  two  supporting  surfaces  differ  in 
size,  they  are  made  in  exactly  the  same  manner,  each  consisting  of 
a  thin  longitudinal  piece  of  spruce  R,  to  which  cross  pieces  of  bamboo 
Q  are  attached.  In  the  smaller  plane,  Fig.  7,  all  the  cross  pieces  are 
of  the  same  size.  In  the  larger  plane,  Fig.  6,  the  outer  strips  S  are 
somewhat  shorter  than  the  others.  Their  length  is  2J  inches,  whereas 
the  length  of  the  strips  Q  is  3J  inches.  In  order  to  allow  for  the  more 
gradual  tapering  of  the  plane,  around  the  outer  ends  of  the  longi- 
tudinal strips  R  and  the  ribs  Q  a  strip  of  bamboo  0  is  tied.  The 


Fig.  6.      Details  of  Main  Plane 
of  Aeroplane  Model 


Fig.  7.      Details  of  Smaller 
Plane  of  Aeroplane  Model 


frame,  composed  of  the  longitudinal  strip  and  cross  strips,  is  then 
covered  with  bamboo  paper,  parchment  paper,  or  any  other  stiff 
light  paper,  which  is  glued  in  place. 


572 


BUILDING  AND  FLYING  AN  AEROPLANE 


The  forward  or  smaller  plane  has  a  spread  of  8J  inches  and  a 
depth  of  3£  inches.  The  main  plane  has  a  spread  of  20  inches  and 
a  depth  of  3J  inches  at  the  widest  portion.  The  author  has  made 
experiments  which  lead  him  to  believe  that  the  tapering  form  given 
to  the  outer  edge  of  the  plane  improves  both  the  stability  and  endur- 
ance of  the  machine. 

The  planes  are  slightly  arched,  although  it  will  be  found  that 
flat  planes  will  also  give  good  results.  The  rear  edge  of  the  main 
plane  should  be  placed  4J  inches  distant  from  the  forward  edge  of 
the  propeller  block  E^ 

The  front  plane  must  have  a  slight  angle  of  incidence,  just  how 
much  depends  upon  the  weight  of  the  machine,  the  manner  in  which 
it  is  made,  and  various  other  factors.  This 
angle  of  incidence  is  obtained  by  resting  the 
front  portion  of  the  plane  on  two  small  blocks 
N,  Figs.  1  and  2,  which  are  fastened  to  the 
top  of  the  main  strip  A  by  strong  thread  and 
glue. 

The  height  of  the  blocks  N  should  be 
about  |  inch,  although  this  will  necessarily 
vary  with  the  machine.  The  blocks  should 
be  placed  approximately  4  inches  from  the 
forward  end  of  the  machine.  The  front  end 
of  the  forward  plane  should  be  elevated  about 
|  inch  above  the  rear  end,  which  rests  directly 
on  the  main  strips.i 

Both  the  front  and  rear  planes  L  and  P   Fig  8    Dcvicc  for  winding 
are  removably  lashed  to  the  frame  by  means      up  Rubber-Band  Motors 
of  ordinary  rubber  bands,  which  may  be  obtained  at  any  stationery 
store.    These  rubber  bands  are  lettered  M  in  Fig.  1. 

Winding  the  Rubber  Strips.  The  rubber  strips  can  be  most 
conveniently  wound  up  by  means  of  an  egg  beater,  slightly  changed 
for  the  purpose,  Fig.  8.  The  beater  and  the  frame  in  which  it  is 
carried  are  entirely  removed,  leaving  only  the  main  rod  E,  which 
is  cut  off  at  the  lower  end  so  that  the  total  length  is  not  more  than 
2  or  3  inches.  The  two  brass  strips  D  on  either  side  of  the  rod, 
which  are  attached  to  the  pinion  Q  meshing  with  the  large  driving 
wheel  //,  are  likewise  retained.  A  washer  F  is  soldered  to  the  rod 


573 


8  BUILDING  AND  FLYING  AN  AEROPLANE 

near  its  upper  end,  so  as  to  limit  the  motion  of  the  small  pinion  G 
and  the  brass  strips  D  attached  to  the  pinion.  Next  a  wire  B  is  bent 
in  the  form  of  a  loop,  through  which  loop  the  central  rod  passes. 
The  ends  of  the  wire  are  soldered  to  the  side  strips  D.  Lastly,  a 
piece  of  wire  C  is  bent  and  soldered  to  the  lower  ends  of  the  side 
strips.  In  order  to  wind  up  a  rubber  strip,  the  strip  is  detached  from 
the  forward  end  of  the  model,  and  the  hook  A  slipped  over  the  wire 
C.  The  opposite  end  of  the  rubber  band  is  held  in  any  convenient 
manner.  Naturally  the  two  strips  must  be  wound  in  opposite  direc- 
tions, so  that  the  two  propellers  will  turn  in  opposite  directions. 
By  stretching  the  rubber  while  it  is  being  wound,  more  revolutions 
can  be  obtained.  It  is  not  safe  to  have  the  propeller  revolve  more 
than  700  times.  The  ratio  of  the  gears  of  the  egg-beater  winder  can 
be  figured  out  so  that  the  requisite  number  of  twists  can  be  given 
to  the  rubber  bands  for  that  particular  number  of  revolutions. 

Model  with  Gasoline  Motor.  The  next  and  somewhat  more 
ambitious  stage  is  the  building  of  a  power-driven  model,  which  has 
been  made  possible  by  the  manufacture  of  miniature  gasoline  motors 
and  propellers  for  this  purpose.  Motors  of  this  kind,  weighing  but 
a  few  pounds  and  capable  of  developing  J  horse -power  or  more,  may 
be  had  complete  with  an  18-inch  aluminum  propeller  and  accessories 
for  about  $45.  As  is  the  case  with  the  rubber-band  driven  model, 
the  monoplane  is  the  simplest  type  to  construct,  and  the  dimensions 
and  details  of  an  aeroplane  of  this  type  are  given  here.  It  will  be 
found  that  a  liberal-sized  machine  is  required  to  support  even  such 
a  small  motor.  The  planes,  Fig.  9,  have  a  spread  of  7  feet  8  inches 
from  tip  to  tip,  each  wing  measuring  3J  feet  by  a  chord  of  15  inches. 
They  are  supported  on  a  front  and  rear  wing  spar  of  spruce,  J  by 
f  inch  in  section,  while  the  ribs  in  both  the  main  plane  and  the 
rear  stabilizing  plane  measure  |  by  f  inch  in  cross  section.  There 
are  eight  of  these  spruce  ribs  in  the  main  plane,  and  they  are  separately 
heated  and  curved  over  a  Bunsen  burner,  or  over  a  gas  stove,  which 
is  the  same  thing.  They  are  then  nailed  to  the  wing  spars  6  inches 
apart.  The  main  spars  of  the  fuselage  are  7  feet  long  and  they  are 
made  of  \-  by  f-inch  spruce,  the  struts  being  placed  1  \  feet  apart, 
measuring  from  the  rear,  with  several  intermediate  struts  to  brace 
the  engine  bed.  Instead  of  using  strut  sockets  for  the  fuselage,  which 
would  increase  the  cost  of  construction  unnecessarily,  a  simple  com- 


574 


BUILDING  AND  FLYING  AN  AEROPLANE 


9 


bination  of  a  three-way  wire  fastener  and  a  wire  nail  may  be  resorted 
to.  The  shape  of  these  fasteners  is  shown  at  A  in  Fig.  9.  They  may 
be  cut  out  of  old  cracker  boxes  or  tin  cans  (sheet  iron)  with  a  pair 
of  shears,  the  holes  in  the  ends  being  made  either  with  a  small  drill 
or  by  driving  a  wire  nail  through  the  metal  placed  on  a  board,  and 


1VB8ER  SPR/ttG 
SQUARE   W/ffG     T/PJ 


XE  M4X.E0  TO 
W/NG-SPAR  W/TH  SMALL 
W/RE/1A/L3 


DHQP  OF  BOLDER 


W/RE  MAJL 


TRUT 


HEAVYT/N  JWXYJ 
W/flE  FASTEMER 


Fig.  9.      Details  of  Power-Driven  Aeroplane  Model 

filing  the  burrs  off  smooth.  A  central  hole  must  also  be  made  for 
the  IJ-inch  wire  nail  which  is  driven  through  the  main  spar  and  the 
fastener  then  slipped  over  it.  As  indicated,  this  nail  also  serves  to 
hold  the  strut.  A  drop  of  solder  will  serve  to  attach  the  fastener  to 
the  nail.  The  front  of  the  fuselage  is  9  inches  square,  tapering  down 
to  6  inches  at  the  rear.  The  height  of  the  camber  of  the  main  planes 


575 


10  BUILDING  AND  FLYING  AN  AEROPLANE 

is  1J  inches  and  the  angle  of  incidence  is  7  degrees,  measured  with 
relation  to  the  fuselage.  The  non-lifting  tail  plane  at  the  rear  which 
is  to  give  the  machine  longitudinal  stability,  measures  4  feet  in  span 
by  14  inches  in  depth. 

The  running  gear  or  front  landing  frame  is  made  of  J-inch 
square  spruce,  all  joints  being  made  with  •&-  by  1-inch  bolts.  Alumi- 
num sleeves,  procurable  at  an  aeronautic  supply  house,  are  employed 
for  the  attachment  of  the  rubber  springs  and  the  radius  rods  running 
down  to  the  wheels,  which  may  also  be  purchased  ready  to  install. 
Old  bicycle  wheels  will  serve  the  purpose  admirably.  Light  steel 
tubes  J  inch  in  diameter  are  used  to  run  these  aluminum  sleeves  on. 
Two  other  steel  tubes  are  joined  to  the  lower  corner  of  the  frame 
by  flattening  them  at  the  ends  and  drilling  with  a  small  hole  for  a 
nail.  These  are  run  diagonally  up  to  the  fuselage  and  serve  as  buffers 
to  take  the  shocks  of  landing.  For  bracing  the  wings,  two  similar 
tubes  are  fastened  to  form  a  pyramid  on  top  of  the  main  plane  just 
back  of  the  engine.  From  these,  guys  are  run  to  the  wings  as  shown. 
The  engine  bed  is  made  of  J-  by  J-inch  white  pine,  and  to  make  it 
solid  it  is  carried  as  far  back  as  the  rear  edge  of  the  main  plane.  The 
batteries  and  coil  are  directly  attached  to  this  plane,  care  being 
taken  in  their  placing  to  preserve  the  balance  of  the  machine.  The 
rudder  measures  14  inches  square  and  is  made  of  f-inch  square  spruce, 
reinforced  with  tin  at  the  joints,  as  it  is  necessary  to  make  the  frame 
perfectly  rigid.  Both  sides  are  covered  with  fabric.  In  this  case 
a  1 -horse-power  motor  furnishes  the  necessary  energy  and  it  is 
fitted  with  an  18-inch  aluminum  propeller  which  it  is  capable  of  turn- 
ing at  2,400  r.  p.  m.  The  carbureter  and  gas  tank  are  made  integral, 
and  the  gasoline  and  oil  are  both  placed  in  this  tank  in  the  propor- 
tion of  about  four  parts  to  one,  in  order  to  save  the  weight  of  an 
extra  tank  for  oil. 

Flights  of  half  a  mile  are  possible  with  this  model  in  calm  weather, 
but  a  great  deal  of  measuring  and  testing  of  the  fuel  is  necessary  in 
order  to  regulate  the  flight,  and  "grass-cutting"  should  be  practiced 
by  the  builder  in  order  to  properly  regulate  the  machine.  Trials 
have  shown  that  the  flat  non-lifting  tail  on  the  fuselage  gives  excellent 
longitudinal  stability,  the  machine  rising  nicely  and  making  its 
descent  very  easy  angle,  so  that  it  is  seldom  damaged  by  violent  col- 
lisions in  landing. 


576 


BUILDING  AND  FLYING  AN  AEROPLANE  11 

BUILDING  A  GLIDER 

The  building  of  hand-  or  power-driven  models  does  not  suffice 
to  give  that  personal  experience  that  most  students  are  desirous  of 
obtaining.  The  best  method  of  securing  this  is  to  build  a  glider 
and  practice  with  it.  Any  flying  machine  without  a  motor  is  a  glider 
and  the  latter  is  the  basis  of  the  successful  aeroplane.  In  the  building 
of  an  aeroplane  the  first  thing  constructed  is  the  glider,  i.  e.,  the  frame, 
main  planes,  stabilizing  planes,  elevators,  rudders,  etc.  It  is  only  by 
the  installation  of  motive  power  that  it  becomes  a  flying  machine. 
The  biplane  will  be  found  the  most  satisfactory  type  of  glider  as  it 
is  more  compact  and  therefore  more  easily  handled,  which  is, of  great 
importance  for  practicing  in  a  wind.  The  generally  accepted  rule  is 
that  152  square  feet  of  surface  will  sustain  the  weight  of  the  average 
•man,  about  170  pounds,  and  it  will  be  apparent  that  the  length  of 
the  glider  will  have  to  be  greater  if  this  surface  is  to  be  in  the  form 
of  a  single  plane  than  if  the  same  amount  is  obtained  by  incor- 
porating it  in  two  planes — the  biplane.  A  glider  with  a  .span  of  20 
feet  and  a  chord  of  4  feet  will  have  a  surface  of  152  square  feet.  So 
far  as  learning  to  balance  and  guide  the  machine  are  concerned,  this 
may  be  mastered  more  readily  in  a  small  glider  than  in  a  large  one,  so 
that  there  is  no  advantage  in  exceeding  these  dimensions — in  fact, 
rather  the  reverse,  as  the  larger  construction  would  be  correspond- 
ingly more  difficult  to  handle.  The  materials  necessary  consist  of 
a  supply  of  spruce,  linen  shoe  thread,  metal  sockets,  piano  wire, 
turnbuckles,  glue,  ^and  closely-woven,  light  cotton  fabric  for  the 
covering  of  the  planes. 

Main  Frame.  The  main  frame  or  box  cell  is  made  of  four  hori- 
zontal beams  of  spruce  20  feet  long  and  1 J  by  f  inch  in  section.  They 
must  be  straight-grained  and  perfectly  free  from  knots  or  other 
defects.  If  it  be  impossible  to  obtain  single  pieces  of  this  length, 
they  may  be  either  spliced  or  the  glider  may  be  built  in  three  sections, 
consisting  of  a  central  section  8  feet  long,  and  two  end  sections  each 
6  feet  in  length,  this  form  of  construction  also  making  the  glider 
much  easier  to  dismantle  and  stow  in  a  small  space.  In  this  case, 
the  ends  of  the  beams  of  each  end  section  are  made  to  project  beyond 
the  fabric  for  10  inches  and  are  slipped  into  tubes  bolted  to  corre- 
sponding projections  of  the  central  section.  These  tubes  are  drilled 


577 


12  BUILDING  AND  FLYING  AN  AEROPLANE 

with  three  holes  each  and  bolts  are  passed  through  these  holes  and 
corresponding  holes  in  the  projecting  ends  after  they  have  been 
fitted  into  the  tubes,  and  drawn  up  tightly  with  two  nuts  on  each 
bolt  to  prevent  shaking  loose.  Ordinary  ^-inch  stove  bolts  will 
serve  very  nicely  for  this  purpose.  The  upper  and  lower  planes 
forming  the  box  cell,  are  held  apart  by  12  struts,  4  feet  long  by  f  inch 
diameter,  preferably  of  rounded  or  oval  form  with  the  small  edge 
forward  to  minimize  the  head  resistance.  It  is  only  necessary  to 
space  these  equally,  starting  from  both  ends;  this  will  bring  the 
splices  of  the  demountable  sections  in  the  center  of  the  square  on 
either  side  of  the  central  section.  The  main  ribs  are  3  feet  long  by 
1J-  by  |-inch  section  and  their  placing  should  coincide  with  the 
position*  of  the  struts.  Between  these  main  ribs  are  placed  41  small 
ribs,  equally  spaced  and  consisting  of  pieces  4  feet  long  by  J  inch 
square.  These,  as  well  as  all  the  other  pieces,  should  have  the  sharp 
edges  of  the  square  rounded  off  with  sand  paper.  The  ribs  should 
have  a  camber  of  2  inches  in  their  length  and  the  simplest  method 
of  giving  them  this  is  to  take  a  piece  of  plank,  draw  the  desired  curve 
on  it,  and  then  nail  blocks  on  both  sides  of  this  curve,  forming  a 
simple  mould.  The  rib  pieces  should  then  be  steamed,  bent  into  this 
mould,  and  allowed  to  dry,  when  they  will  be  found  to  have  per- 
manently assumed  the  desired  curvature.  Meanwhile,  all  the 
other  pieces  may  be  shellaced  and  allowed  to  dry. 

Assembling  the  Planes.  To  assemble  the  glider,  the  beams  are 
laid  out  on  a  floor,  spaced  the  exact  distance  apart,  i.  e.,  3  feet, 
and  exactly  parallel — in  the  demountable  plan,  each  section  is 
assembled  independently.  The  main  ribs  are  then  glued  in  place 
and  allowed  to  set,  after  which  they  are  strongly  bound  in  place  with 
the  linen  thread,  and  the  various  layers  of  thread  given  a  coating  of 
hot  glue  as  they  are  put  on.  This  method  is  not  arbitrary,  but  it  is 
simple  and  gives  the  lightest  form  of  construction.  If  desired,  tie- 
plates,  clamps,  or  any  other  light  method  of  fastening  may  be 
employed.  This  also  applies  to  the  ribs.  They  are  assembled  by 
placing  them  flush  with  the  front  beam  and  allowing  them  to  extend 
back  a  foot  beyond  the  rear  beam,  arched  side  up  in  every  case.  They 
may  be  glued  and  bound  with  thread,  held  by  clamps,  or  nailed  or 
screwed  into  place,  care  being  taken  to  first  start  a  hole  in  the  beam 
with  an  awl  and  to  dip  the  nails  in  soft  soap  to  prevent  splitting  the 


578 


BUILDING  AND  FLYING  AN  AEROPLANE  13 

wood.  Twenty-one  ribs,  spaced  one  foot  apart,  are  used  in  the  upper 
plane,  and  20  in  the  lower,  owing  to  the  space  left  for  the  operator  in 
the  latter.  For  fastening  the  two  planes  together,  whether  as  a 
whole  or  in  sectional  units,  24  aluminum  sockets  will  be  required. 
These  may  be  purchased  either  ready  to  fit,  or  an  effective  substitute 
made  by  sawing  short  lengths  of  steel  tubing,  slitting  them  with 
the  hack  saw  an  inch  from  the  bottom,  and  then  flattening  out 
and  drilling  the  right-angle  flanges  thus  formed  to  take  screws  for 
attaching  the  sockets  to  the  beams.  In  case  these  sockets  are  bought, 
they  will  be  provided  with  eye  bolts  for  the  guy  wires ;  if  homemade, 
they  may  have  extra  holes  drilled  in  the  edges  of  the  flanges  for  this 
purpose  or  some  simple  wire  fastener  such  as  that  described  in  con- 
nection with  the  power-driven  model  may  be  used,  heavier  metal, 
however,  being  employed  to  make 
them.  The  sockets  should  all  be 
screwed  to  the  beams  at  the 
proper  points  and  then  the  struts 
should  be  forced  into  them.  The 
next  move  is  to  "tie"  the  frame 
together  with  guy  wires,  No.  12 
piano  wire  being  employed  for  this 
purpose.  Each  rectangle  is  trussed  Fig.  10.  wrong  and  Right  Way  of 

,.  ,  .  Making  a  Wire  Joint 

by    running    diagonal    guy    wires 

from  each  corner  to  its  opposite.  To  pull  these  wires  taut,  a  turn- 
buckle  should  be  inserted  in  each  and  after  the  wire  has  been  pulled 
as  tightly  as  possible  by  hand,  it  should  be  wound  upon  itself  to 
make  a  good  strong  joint,  as  shown  at  B,  Fig.  6.  A  fastening  as 
shown  at  A  will  pull  out  under  comparatively  little  strain  and  is  not 
safe.  As  is  the  case  with  most  of  the  other  fittings,  these  turn- 
buckles  may  be  bought  or  made  at  home,  the  simple  bicycle  type  of 
turnbuckle  mentioned  in  connection  with  "Building  a  Curtiss," 
being  admirably  adapted  to  this  purpose.  In  fact,  the  construction 
of  the  latter  will  be  found  to  cover  the  requirements  of  the  glider, 
except  that  the  ribs  are  simpler  and  lighter,  as  already  described, 
and  no  provision  for  the  engine  or  similar  details  is  necessary.  All 
the  guy  wires  must  be  tightened  until  they  are  rigid,  and  the  proper 
degree  of  tension  for  them  may  be  simply  determined  in  the  follow- 
ing manner: 


579 


14  BUILDING  AND  FLYING  AN  AEROPLANE 

After  the  entire  frame  is  wired,  place  each  end  of  it  on  a  saw  horse 
so  as  to  lift  it  two  or  three  feet  clear  of  the  floor.  Stand  in  the  open- 
ing of  the  central  section,  as  if  about  to  take  a  glide,  and  by  grasping 
the  forward  central  struts,  raise  yourself  from  the  floor  so  as  to  bring 
your  entire  weight  upon  them.  If  properly  put  together  the  frame 
will  be  rigid  and  unyielding,  but  should  it  sag  even  slightly,  the  guy 
wires  must  be  uniformly  tightened  until  even  the  faintest  perceptible 
tendency  to  give  under  the  weight  is  overcome. 

Stretching  the  Fabric.  The  method  of  attaching  the  fabric  will 
be  determined  by  whether  the  glider  is  to  be  one  piece  or  sectional, 
and  the  expense  for  this  important  item  of  material  may  be  as  little 
or  as  much  as  the  builder  wishes  to  make  it.  Some  employ  rubberized 
silk,  others  special  aeronautic  fabrics,  but  for  the  purposes  of  the 
amateur,  ordinary  muslin  of  good  quality,  treated  with  a  coat  of 
light  varnish  after  it  is  in  place,  will  be  found  to  serve  all  purposes. 
The  cloth  should  be  cut  into  4-foot  strips,  glued  to  the  front  horizontal 
beams,  stretched  back  tightly,  and  tacked  to  both  the  rear  horizontal 
beams  and  to  the  ribs.  Tacks  should  also  supplement  the  glue  on 
the  forward  beams  and  the  upholstery  style  should  be  used  to  pre- 
vent tearing  through  the  cloth.  In  case  the  glider  is  built  in  sections, 
the  abutting  edges  of  the  cloth  will  have  to  be  reinforced  by  turning 
it  over  and  stitching  down  a  strip  one  inch  wide,  and  it  will  make 
this  edge  stronger  if  an  extra  strip  of  loose  fabric  be  inserted  under 
the  turn  before  sewing  it  down.  Eyelets  must  then  be  made  along 
these  edges  and  the  different  sections  tightly  laced  together  when 
assembling  the  glider.  It  is  also  desirable  to  place  a  strip  of  cloth  or 
light  felt  along  the  beams  under  the  tacks  to  prevent  the  cloth  from 
tearing  out  under  the  pressure. 

To  form  a  more  comfortable  support  for  the  operator,  two  arm 
pieces  of  spruce,  3  feet  by  1  inch  by  If  inches,  should  be  bolted  to 
the  front  and  rear  beams  about  14  inches  apart  over  the  central 
opening  left  in  the  lower  plane.  These  will  be  more  convenient  than 
holding  on  to  the  struts  for  support,  as  it  will  not  be  necessary  to 
spread  the  arms  so  much  and  there  will  be  more  freedom  for  manipu- 
lating the  weight  to  control  the  glider  in  flight.  In  using  the  struts, 
it  is  customary  to  grasp  them  with  the  hands,  while  with  the  arm 
pieces,  as  the  name  implies,  the  operator  places  his  arms  over  them, 
one  of  the  strips  coming  under  each  armpit.  After  the  fabric  has 


580 


BUILDING  AND  FLYING  AN  AEROPLANE  15 

been  given  a  coat  of  varnish  on  the  upper  side  and  allowed  to  dry, 
the  glider  is  ready  for  use.  The  cost  of  the  material  should  be  about 
$30  to  $40,  depending  upon  the  extent  to  which  the  builder  has 
relied  upon  his  own  ingenuity  in  fashioning  the  necessary  fittings — 
in  any  case,  it  will  be  less  than  the  amount  required  for  the  purchase 
of  the  engine  alone  for  a  power-driven  model. 

Glider  with  Rudder  and  Elevator.  It  will  be  noted  that  this  is 
the  simplest  possible  form  of  glider  in  that  it  is  not  even  provided 
with  a  rudder,  but  for  the  beginning  of  his  gliding  education  the 
novice  will  not  require  this,  as  first  attempts  should  be  confined  to 
glides  over  level  ground  in  moderate,  steady  wind  currents  and  at  a 
modest  elevation.  Some  of  the  best  gliding  flights  made  by  Herring, 
Chanute's  co-worker,  were  in  a  rudderless  glider.  After  having 
mastered  the  rudiments  of  the  art,  the  student  may  go  as  far  as  the 
dictates  of  his  ambition  impel  him  in  the  direction  of  improvements 
in  his  glider,  by  adding  a  rudder,  elevator,  and  warping  control.  In 
fact,  it  is  not  necessary  to  confine  himself  to  the  simple  design  of 
glider  here  outlined  at  all.  He  may  take  either  the  Wright  or  Curtiss 
machines  as  a  model  and  build  a  complete  glider,  following  the 
dimensions  and  general  methods  of  construction  here  given,  though 
these  may  also  be  improved  upon  by  the  man  handy  with  tools, 
bearing  in  mind  that  the  object  to  be  achieved  is  the  minimum  weight 
consistent  with  the  maximum  strength. 

Learning  to  Glide.  The  first  trials  should  be  made  on  level 
ground  and  the  would-be  aviator  should  be  assisted  by  two  com- 
panions to  help  him  in  getting  under  way.  The  operator  takes  a 
position  in  the  center  rectangle,  back  far  enough  to  tilt  up  slightly 
the  forward  edges  of  the  planes.  A  start  and  run  forward  is  made 
at  a  moderate  pace,  the  keepers  carrying  the  weight  of  the  glider 
and  overcoming  its  head  resistance  by  running  forward  at  the  same 
speed.  As  the  glider  cuts  into  the  air,  the  wind  caused  by  running 
will  catch  under  the  uplifted  edges  of  the  curved  planes  and  will 
buoy  it  up,  causing  it  to  rise  in  the  air  taking  the  operator  with 
it.  This  rise  will  be  probably  only  sufficient  to  lift  him  clear  of  the 
ground  a  foot  or  two.  Now  he  projects  his  legs  slightly  forward  so  as 
to  shift  the  center  of  gravity  a  trifle  and  bring  the  edges  of  the  glider 
on  an  exact  level,  parallel  with  the  ground.  This,  with  the  momentum 
acquired  at  the  start,  will  keep  the  glider  moving  forward  for  some 


581 


16          BUILDING  AND  FLYING  AN  AEROPLANE 

distance.  When  the  weight  of  the  operator  is  slightly  back  of  the 
center  of  gravity,  the  leading  edges  of  the  planes  are  tilted  up  some- 
what, increasing  the  angle  of  incidence  and  in  consequence  the  pres- 
sure under  the  planes,  causing  the  glider  to  rise,  and  if  the  glide  is 
being  made  into  a  wind,  as  should  always  be  the  case,  quite  a  height 
may  be  reached  as  the  result  of  this  energy.  Once  it  ceases,  the  ten- 
dency to  a  forward  and, up  ward  movement  is  lost,  and  it  is  to  prolong 
this  as  much  as  possible  that  the  operator  shifts  the  center  of  gravity 
to  bring  the  machine  on  an  even  keel,  or  where  at  a  little  height, 
slightly  below  this,  giving  it  a  negative  angle  of  incidence,  which 
permits  him  to  coast  down  the  air  until  sufficient  speed  is  acquired 
to  reverse  the  angle  of  incidence  and  again  rise  so  as  to  provide  a 
"hill"  for  another  coast,  thus  prolonging  the  flight  considerably. 
To  put  it  in  the  simplest  language,  when  the  operator  moves  back- 
ward, shifting  the  center  of  gravity  to  the  rear,  the  planes  are  tilted 
so  that  they  catch  or  "scoop  up"  the  advancing  air  and  rise  upon  it, 
whereas  when  he  moves  forward  and  the  planes  tilt  downward,  this 
air  is  "spilled"  out  behind  and  no  longer  acts  as  a  support,  and  the 
glider  coasts,  either  until  the  ground  is  reached  or  enough  momentum 
is  gained  to  again  mount  upon  the  wind.  A  comparatively  few  flights 
will  suffice  to  make  the  student  proficient  in  the  control  of  his  appa- 
ratus by  his  body  movements,  not  only  as  concerns  the  elevating 
and  depressing  of  the  planes  to  ascend  or  descend,  corresponding 
to  the  use  of  the  elevator  on  a  power  machine,  but  also  actual 
steering,  which  is  accomplished  by  lateral  movement  to  the  left  or 
right. 

Stable  equilibrium  is  one  of  the  chief  essentials  to  successful 
flight  and  this  can  not  be  maintained  in  an  uncertain,  gusty  wind, 
especially  by  the  novice.  The  beginner  should  certainly  not  attempt 
a  glide  unless  the  conditions  are  right.  These  are  a  clear,  level  space 
without  obstructions  such  as  trees,  and  a  steady  wind  not  exceeding 
12  miles  per  hour.  When  a  reasonable  amount  of  proficiency  has 
been  attained  in  the  handling  of  the  glider  over  level  ground,  the 
field  of  practice  may  be  changed  to  some  gentle  slope.  In  starting 
from  this,  it  will  be  found  easier  to  keep  the  glider  afloat,  but  the 
experience  at  first  will  prove  startling  to  the  amateur,  for  as  the 
glider  sails  away  from  the  top  of  the  slope,  the  distance  between  him 
and  the  ground  increases  so  rapidly  that  he  will  imagine  himself  at 


582 


BUILDING  AND  FLYING  AN  AEROPLANE  17 

a  tremendous  height,  but  by  preserving  the  balance  and  otherwise 
manipulating  his  weight  in  the  manner  taught  by  the  practice  over 
the  level,  a  nice  flight  of  much  greater  distance  will  be  made  and  the 
machine  will  gradually  settle  down  to  the  ground  much  farther  away 
from  the  starting  place  than  was  possible  in  the  earlier  trials,  this  being 
one  of  the  great  advantages  of  starting  from  an  elevation.  There  is 
nothing  that  will  fit  the  beginner  so  well  for  the  actual  handling  of 
a  power  machine  as  a  thorough  course  of  gliding  flights,  and  it  is 
recommended  that  those  who  build  gliders  become  proficient  in  their 
use  before  attempting  to  pilot  an  aeroplane,  whether  of  their  own 
make  or  not. 

A  further  step  in  advance  is  the  actual  building  of  a  full-fledged 
power  machine,  and  for  those  who  desire  a  simple  and  comparatively 
inexpensive  type,  requiring  very  little  work  that  can  not  be  per- 
formed in  the  home  workshop,  a  description  of  the  construction  of  a 
Curtiss  biplane  is  given,  while  for  those  who  are  more  ambitious 
and  also  have  greater  financial  resources,  the  details  of  the  building 
of  a  Bleriot  monoplane  are  given. 

BUILDING  A  CURTISS  BIPLANE 

Cost.  First  of  all,  the  prospective  builder  will  want  to  know 
the  cost.  The  best  answer  to  this  is  that  the  machine  will  cost  all 
its  builder  can  afford  to  spend  upon  it  and  probably  a  little  more, 
as  the  man  to  whom  the  expense  is  not  of  vital  consideration  will 
doubtless  not  undertake  its  construction.  Speaking  generally,  and 
there  can  be  nothing  very  definite  about  it,  in  view  of  the  great 
difference  in  the  conditions,  an  expenditure  of  three  to  four  hundred 
dollars  will  cover  the  complete  outlay  for  everything  but  the  motor. 
If  the  builder  has  the  time  and  facilities  for  doing  all  the  work  him- 
self, this  amount  may  be  reduced  very  materially.  On  the  other 
hand,  if  he  finds  it  necessary  to  purchase  most  of  the  material  in 
form  ready  to  assemble,  it  may  exceed  this.  But  it  will  be  a  great 
aid  to  many  to  know  that  there  is  practically  nothing  about  the 
modern  aeroplane  which  can  not  be  found  in  stock  at  one  of  the 
aeronautic  supply  houses.  This  makes  it  possible  for  many  to 
undertake  the  construction  of  a  machine  to  whom  it  would  not  be 
feasible,  or  at  least  not  an  attractive  project  in  view  of  the  time 
involved,  were  it  necessary  to  make  every  part  at  home.  So  far 


583 


BUILDING  AND  FLYING  AN  AEROPLANE 


as  becoming  involved  in  any 
legal  difficulties  is  concerned 
owing  to  existing  patents, 
the  student  need  not  worry 
himself  about  this  in  at- 
tempting the  construction  of 
a  Curtiss  biplane,  so  long  as 
he  restricts  the  use  of  his 
machine  to  experimental  pur- 
poses and  does  not  try  to 
compete  with  the  patentees 
in  their  own  field — that  of 
exhibiting  and  selling  ma- 
chines. 

General  Specifications.  Just 
how  long  it  will  take  to  com- 

2  plete  such  a  machine  will  de- 
pend very  largely  upon  the 
skill  of  the  builder  and  the  ex- 
tent of  his  resources  for,  as  al- 
ready mentioned,  the  expense 
may  be  cut  down  by  making 
all  the  necessary  parts  at 
home,  but  it  will  naturally  be 

If  at  the  sacrifice  of  a  great  deal 
of  time.  For  instance,  the 
oval  struts  and  beams  may  be 
bought  already  shaped  from 
the  local  planing  mill,  or  they 
may  be  shaved  down  from  the 
rough  by  hand.  Turnbuckles 
can  be  made  from  bicycle 
spokes  and  nipples  and  strips 
of  sheet  steel,  or  they  can  be 
bought  at  12  to  15  cents  each. 
As  a  hundred  or  more  of  them 
are  needed,  their  cost  is  quite 
a  substantial  item. 


584 


BUILDING  AND  FLYING  AN  AEROPLANE 


19 


Aeroplane  construction  doubtless  impresses  the  average  observer 
as  being  something  shrouded  in  considerable  mystery — something 
about  which  there  is  no  little  secrecy.  Quite  the  contrary  is  the  case 
in  reality.  Any  man  who  is  fairly  proficient  as  a  carpenter  and 
knows  how  to  use  the  more  common  machinist's  tools,  such  as  taps 


l 


Fig.  12.      Plan  and  Side  Elevation  of  Curtiss  Biplane 

and  dies,  drills,  hacksaw,  and  the  like,  will  find  no  difficulty  in  con- 
structing the  machine  of  which  the  details  are  given  here.  Having 
completed  its  building,  he  will  have  to  draw  upon  his  capital  to 
supply  the  motor.  One  capable  of  developing  25  to  30  horse-power 
at  1,000  to  1,200  r.  p.  m.  will  give  the  machine  considerable  speed, 
as  it  will  be  recalled  that  Curtiss  made  a  number  of  his  first  flights 


585 


20 


BUILDING  AND  FLYING  AN  AEROPLANE 


with  a  25-horse-power  motor.  As  to  the  weight,  the  lighter  the 
better,  but  400  pounds  for  the  complete  power  plant  will  not  be 
excessive.  The  machine  can  sustain  itself  in  the  air  with  less  power 
than  that  mentioned,  but  with  a  heavy,  low-power  motor  it  will  be 
sluggish  in  action.  This  is  an  advantage  for  the  amateur,  rather 
than  otherwise,  as  it  will  provide  him  with  an  aeroplane  that  will 
not  be  apt  to  get  away  from  him  during  his  first  trials,  thus  making 
it  safer  to  learn  on. 

The  Curtiss  biplane  has  a  spread  of  30  feet,  the  main  planes  or 
wings  being  divided  into  sections  of  a  length  equal  to  the  distance 


SMALL    ff/B 
Fig.  13.      Details  of  Main  and  Small  Ribs,  Curtiss  Biplane 

between  struts,  Figs.  11  and  12.  There  are  five  of  these  sections,  each 
measuring  six  feet.  The  struts  can  be  taken  out  and  the  sections 
laid  flat  on  each  other  for  storage.  The  framework  for  the  front  and 
rear  rudders  can  also  be  jointed,  if  desired,  making  it  possible  to 
store  the  machine  in  small  compass.  The  longest  parts  of  the  machine, 
when  taken  apart,  are  the  two  diagonal  beams  running  from  the 
front  wheel  back  to  the  engine  bed,  and  the  skid.  The  horizontal 
front  rudder  is  packed  intact.  The  vertical  rear  rudder  is  unhung 
and  laid  flat  on  the  tail.  Two  men  can  take  the  machine  apart  in 
a  few  hours,  and  can  reassemble  it  in  a  day.  Whether  these  particular 


586 


BUILDING  AND  FLYING  AN  AEROPLANE 


21 


TABLE    I 

Relative  Strength  of  Clear  Spruce  and  Elm  as  Demon= 
strated  by  Tests 


Material 

Size  of  Pieces 
(Inches) 

Breaking 
Strain 
(Pounds) 

Weight  of 
Piece 
(Ounces) 

Elm 

U    XU    X12 

900 

5| 

Spruce 

U    Xl|    X12 

900 

4l 

Elm 

1&X1&X12 

880 

4f 

Spruce 

1&X1&X12 

760 

31 

Elm 

1       XI     X12 

450 

4 

Spruce 

1      XI     X12 

600 

3* 

Elm 

HXU    X12 

390 

3i 

Spruce 

HXH    X12 

475 

3 

Elm 

f  XI    X12 

275      . 

2* 

Spruce 

f  X  f    X12 

280 

2i 

Elm 

^XH    X12 

175 

21- 

Spruce 

tkXH    X12 

175 

2 

features  of  construction  are  covered  by  patents  can  not  be  said,  as 
Curtiss  has  declined  to  commit  himself  regarding  any  rights  he 
may  have  to  them. 

Ribs.  Two  distinct  types  of  ribs  are  used,  main  ribs  and  small 
ribs,  both  of  the  same  curvature,  Fig.  13.  The  main  ribs  are  used 
between  pairs  of  struts,  to  hold  apart  the  front  and  rear  beams;  they 
are  heavy  enough  to  be  quite  rigid.  Three  to  four  small  ribs  are  laid 
across  each  section  of  the  planes,  between  the  pairs  of  main  ribs,  to 
give  the  cloth  the  proper  curvature,  and  to  maintain  it  in  the  form 
desired.  The  main  ribs  are  built  up  of  six  J-inch  laminations  of  wood 
J  inch  wide  and  securely  glued  together.  The  small  ribs  are  made  of 
three  layers  \  inch  wide. 

The  first  part  of  the  actual  construction  will  be  the  making  of 
these  laminated  ribs,  but  before  describing  this  detail,  the  question 
of  suitable  material  should  be  well  considered.  Both  weight  and 
strength  must  be  figured  on  and  this  limits  the  choice  to  a  few  kinds 
of  wood.  Of  these  spruce  and  elm  are  the  best  available,  with  the 
occasional  use  of  ash  to  give  greater  rigidity.  Spruce  is,  of  course, 
the  first  choice.  This  wood  was  once  considered  as  having  no 
great  strength,  but  a  series  of  careful  tests  showrs  this  belief  to 
be  unfounded.  With  the  exception  of  the  bed,  or  support  for  the 


587 


22 


BUILDING  AND  FLYING  AN  AEROPLANE 


motor  and  a  few  other  parts,  the  Wright  machines  are  constructed 
wholly  of  spruce. 

Table  I  gives  results  of  tests  made  with  spruce  from  Washington 
and  Oregon,  and  with  elm  from  Michigan  and  Indiana.  Testing 
scales  were  employed,  the  pieces  being  supported  at  their  ends  with 
the  load  in  the  center. 

These  tests  were  made  with  clear  wood  in  each  case,  as  knots 
naturally  decrease  the  strength  of  a  piece  greatly,  this  depending  on 
their  size  and  location. 


Fig.  14.      Details  of  Rib  Tress,  Curtiss  Biplane 

Before  proceeding  with  the  ribs  themselves,  the  press  for  giving 
them  the  proper  curvature  must  be  made.  Take  a  good  piece  of 
oak,  ash,  or  other  solid  wood,  8  inches  wide  by  5  feet  long,  and 
dressed  all  over.  On  the  side  of  the  piece  lay  out  the  curve,  the 
dimensions  of  which  are  illustrated  in  Fig.  14.  First,  rule  the  hori- 
zontal, or  chord  line,  on  it,  marking  off  4  feet  6  inches  on  this  line, 
equidistant  from  each  end.  Then  divide  the  chord  into  G-inch 
sections  and,  at  the  point  of  each  6-inch  section,  erect  perpendiculars 
beginning  at  the  rear,  f  inch,  If  inches,  2  inches,  and  so  on,  as  indi- 
cated on  the  drawing.  The  upper  ends  of  these  perpendiculars  will 


588 


BUILDING  AND  FLYING  AN  AEROPLANE  23 

form  locating  points  for  the  curve.  Through  them  draw  a  smooth 
curve  as  shown,  continuing  it  down  through  the  chord  at  each  end. 
Take  the  piece  with  the  curve  thus  marked  on  it  to  the  local  planing, 
sash  and  blind,  or  sawmill — any  plant  equipped  with  a  band  saw— 
and  have  it  cut  apart  along  the  curve.  This  will  cost  little  or  nothing 
— acquaintance  will  obtain  it  as  a  favor,  and  acquaintance  with  any 
wood-working  concern  in  the  aeroplane  builder's  home  town  will 
be  of  great  aid.  Failing  this  aid,  the  operation  may  be  carried  out 
with  a  hand  saw  (rip) ,  but  the  job  will  not  be  as  neat  and  will  have 
to  be  cleaned  up  with  a  draw  knife  and  sand  paper,  taking  care  to 
preserve  the  outline  of  the  curve  as  drawn.  As  the  rib  press  is  really 
a  mould  or  pattern  from  which  all  the  ribs  are  to  be  bent  to  a  uniform 
curvature,  care  must  be  taken  in  its  construction. 

To  clamp  the  two  halves  of  the  press  together,  a  dozen  machine 
bolts  will  be  required;  they  should  measure  |X15  inches.  If  obtain- 
able, eye  bolts  will  be  found  more  convenient  as  they  may  be  turned 
up  with  but  one  wrench  and  a  bar.  The  steel  straps  are  f  by  1J  by 
10  inches  long  with  f-inch  holes  drilled  9  inches  apart  to  centers, 
to  enclose  the  S-inch  pieces. 

Obtain  a  sufficient  supply  of  boards  of  reasonably  clear  spruce, 
J  inch  thick,  6  to  7  inches  wide,  and  at  least  4  feet  9  inches  long  (dress- 
ed both  sides),  to  make  all  the  ribs  necessary  both  small  and  large. 
This  material  should  be  purchased  from  the  mill  as  it  is  out  of  the 
question  to  attempt  to  cut  the  ribs  from  larger  sizes  by  hand.  Buy 
several  pounds  of  good  cabinet  makers'  glue  and  a  water-jacketed 
gluepot.  This  glUe  comes  in  sheets  and  in  numerous  grades — a 
good  quality  should  be  used,  costing  from  40  to  50  cents  a  pound  if 
bought  in  a  large  city.  Laminating  the  ribs  in  this  manner  and 
gluing  them  together  is  not  only  the  quickest  and  easiest  method 
of  giving  them  the  proper  curve,  being  much  superior  to  steam  bend- 
ing, but  is  also  stronger  when  well  done,  as  the  quality  of  the  material 
can  be  watched  more  closely. 

Start  with  the  making  of  the  small  ribs;  apply  the  glue  thin  and 
piping  hot  in  a  generous  layer  to  three  boards  with  a  good-sized  flat 
paint  or  varnish  brush.  Omit  on  the  upper  surface  of  third  board 
and  apply  between  three  others,  Fig.  13.  This  will  give  two  series 
of  three  each  in  the  press.  Tighten  up  the  end  bolts  first,  as  the 
upper  part  of  the  press  near  the  top  of  the  curve  is  likely  to  be  weak 


589 


24  BUILDING  AND  FLYING  AN  AEROPLANE 

unless  liberally  proportioned.  Then  turn  down  the  nuts  on  the 
other  bolts.  Do  not  attempt  to  turn  any  one  of  them  as  far  as  it 
will  go  the  first  time,  but  tighten  each  one  a  little  at  a  time,  thus 
gradually  making  the  compression  over  the  whole  surface  as  nearly 
uniform  as  possible.  This  should  be  continued  until  the  glue  will 
no  longer  ooze  out  from  between  the  boards,  indicating  that  they  are 
in  close  contact.  Twenty-four  hours  should  be  allowed  for  drying, 
and  when  taken  out  the  cracks  between  the  boards  should  be  almost 
invisible  in  the  finished  ribs. 

Have  the  laminated  boards  cut  by  a  power  rip  saw  at  the  planing 
mill,  to  the  dimensions  shown  in  the  drawing,  making  an  allowance 
of  J  inch  for  the  width  of  the  saw  blade  at  each  cut  in  calculating 
the  number  of  ribs  which  can  be  cut  from  each  board.  In  addition, 
a  margin  should  be  allowed  at  each  side,  as  it  is  impractical  to  get 
all  the  thin  boards  squarely  in  line.  For  the  main  ribs,  apply  the 
glue  between  all  six  boards,  clamp  and  dry  in  the  same  manner. 
Thirty  small  ribs  will  be  required,  if  three  are  used  in  each  section, 
and  forty  if  four  are  specified,  while  twelve  main  ribs  will  be  needed 
for  standard  construction,  and  sixteen  if  the  quick-demountable 
plan  referred  to  is  followed.  It  is  advisable  to  make  several  extra 
ribs  of  each  kind  in  addition.  If  the  builder  has  not  sufficient  faith 
in  spruce  alone,  despite  the  figures  given  in  Table  I,  one  of  the 
laminations,  preferably  the  center,  or  if  two  be  employed,  the  outer 
ones,  may  be  of  ash,  though  this  will  add  considerably  to  the  weight. 

To  prevent  the  ribs  from  splitting  open  at  the  ends,  they  are 
protected  by  light  steel  ferrules,  shown  in  Fig.  15.  When  received  in 
the  rough-sawed  condition  from  the  mill,  the  ribs  must  be  tapered 
at  the  ends  with  a  plane  or  spoke  shave  to  fit  these  ferrules,  and  the 
sharp  edges  should  be  rounded  off.  In  doing  this,  it  must  be  remem- 
bered that  the  upper  surface  of  the  small  ribs  gives  the  curvature 
to  the  cloth  surface,  so  that  any  tapering  must  be  done  on  the  lower 
side.  The  main  ribs  may  be  tapered  from  both  sides,  as  it  is  the 
center  line,  or  crack  between  the  third  and  fourth  laminations,  that 
determines  the  curve.  Every  inch  along  this  line  ^-inch  holes  are 
to  be  drilled  for  the  lacing,  Fig.  15. 

The  ferrules  for  the  front  ends  of  the  small  ribs  are  light  |-inch 
seamless  steel  tubing;  they  may  be  flattened  to  the  proper  shape 
in  a  vise  without  heating  and  are  drilled  with  a  J-inch  hole.  They 


590 


BUILDING  AND  FLYING  AN  AEROPLANE 


25 


are  driven  tight  on  to  the  tapered  ends  of  the  ribs  and  fastened  in 
place  with  a  small  screw.  The  rear-end  ferrules  are  f-inch  lengths 
of  f-inch  tubing,  driven  on  and  drilled  with  a  ^-inch  hole  for  the 
rear-edge  wire.  The  rear  ferrules  of  the  main  ribs  may  be  the  same 
f-inch  tubing  used  for  the  front  of  the  small  ribs;  they  should  be 
cut  off  so  that  their  ends  will  come  in  the  same  line  as  the  holes  in 
the  ends  of  the  small  ribs.  If  the  quick-demountable  plan  be  fol- 
lowed, the  second  main  rib  from  each  end  may  be  left  long  and 

(on  nz  znzi = 


MA/N  R/B  (F/n/shedJ 


SMALL  ft/B(  Finished J 


FRONT  STRUT 
-5? --£*    


-Z 


fiEAFt   STRUT 


SECT/ ON   OF 
STRUT 


SECT/ON  OF 

BEAM 


Fig.  15.      Details  of  Ribs  and  Struts,  Curtiss  Biplane 

drilled  with  a  hole  like  the  small  ribs.  The  front  ferrules  of  the 
main  ribs  should  be  f-inch  tubing  of  heavier  gauge,  drilled  with  a 
J-inch  hole.  The  finished  ribs  are  sandpapered  smooth  and  shel- 
laced or  coated  with  spar  varnish.  The  latter  is  much  more  expensive 
and  slower  in  drying  but  has  the  great  advantage  of  being  weather- 
proof and  will  protect  the  glue  cracks  from  moisture.  The  ferrules 
may  be  painted  with  black  enamel. 

Struts.     Before  going  into  the  detail  of  the  construction  of  the 
remainder  of  the  main  cell  and  its  attached  framing,  a  brief  descrip- 


591 


26 


BUILDING  AND  FLYING  AN  AEROPLANE 


tion  of  its  parts  and  their  relation  to  one  another  will  make  matters 
clearer.  The  upright  struts,  Fig.  15,  which  hold  the  two  planes 
apart,  fit  at  each  end  into  sockets,  which  are  simply  metal  cups  with 
bolts  projecting  through  their  ends,  Fig.  16.  Those  at  the  bottom 
of  the  front  row  of  struts  pass  through  the  eyes  of  the  turnbuckles 
and  connections  for  the  wire  trussing,  then  through  the  flattened 
ferrules  of  the  main  ribs,  and  finally  through  the  beam,  all  being 
clamped  together  with  a  nut.  Those  at  the  top  go  through  the 
turnbuckles  first,  then  through  the  beam,  and  finally  the  rib  ferrule. 
The  bolts  at  the  back  row  of  struts  must  go  through  the  full  thick- 


o 

0 

'• 

— 

1 

e- 

T± 

o 

Fig.  1G.     Details  of  Metal  Parts  of  Curtiss  Biplane 

ness  of  the  main  ribs,  and  so  must  be  longer.  The  drawings,  Figs. 
15  and  16,  show  the  method  of  attachment  of  both  the  main  and 
the  small  ribs  and  illustrate  a  neat  method  of  attaching  the  turn- 
buckles — instead  of  being  strung  on  the  socket  bolt  one  after  another, 
they  are  riveted  to  the  corners  of  a  steel  plate  which  alone  is  clamped 
under  the  socket. 

Beams.  The  beams  are  jointed  at  each  strut  connection,  the 
ends  being  cut  square  and  united  by  a  sheet-steel  sleeve,  a  pattern 
of  which  is  shown  in  Fig.  16,  clamped  on  by  two  small  bolts.  The 
hole  for  the  socket  bolt  is  drilled  half  in  each  of  the  two  abutting 
beams.  As  it  is  very  difficult  to  obtain  long  pieces  of  wood  suf- 


592 


BUILDING  AND  FLYING  AN  AEROPLANE  27 

ficiently  straight  grained  and  free  from  knots  for  the  purpose,  this 
jointed  system  considerably  cheapens  the  construction.  Both  beams 
and  struts  are  of  spruce,  but  to  give  additional  strength,  the  beams 
of  the  middle  section  may  be  ash.  Special  aero  cloth,  rubberized 
fabrics,  or  light,  closely-woven  duck  (racing  yacht  sail  cloth  of  fine 
quality,  this  being  employed  at  first  by  the  Wright  Brothers  in 
their  machines)  forms  the  surfaces  of  the  wings.  The  front  edge  of 
each  section  of  the  surface  is  tacked  to  the  beam  and  the  rear  edge 
is  laced  over  the  rear  wire  already  referred  to,  this  wire  being  stretched 
taut  through  the  holes  in  the  rear  tips  of  the  ribs,  both  main  and 
small.  After  the  cloth  is  stretched  tight,  it  is  tacked  to  the  small 
ribs,  a  strip  of  tape  being  laid  under  the  tack  heads  to  prevent  the 
cloth  from  pulling  away  from  under  them.  If  the  aeroplane  is  intended 
to  be  taken  apart  very  often,  the  standard  design  as  shown  by  the 
large  drawings,  Figs.  11  and  12,  may  be  modified  so  as  to  make  it 
unnecessary  to  unlace  the  cloth  each  time.  This  is  arranged  by 
regarding  the  two  outer  sections  at  each  end  of  the  plane  as  one, 
and  never  separating  them.  Additional  main  ribs  are  then  pro- 
vided at  the  inner  ends  of  these  sections,  and  are  attached  directly 
to  the  beams,  instead  of  being  clamped  under  the  strut  sockets. 
In  taking  the  machine  apart,  the  struts  are  pulled  from  the  sockets, 
leaving  the  latter  in  place.  It  will  then  be  an  advantage  to  shorten 
the  main  planes  somewhat,  say  3  inches  on  each  section,  so  that  the 
outer  double  sections  will  come  under  the  "  12-foot  rule"  of  the  Express 
Companies. 

Running  Gear.  Three  wheels  are  provided — one  in  front  under 
the  outrigger  and  two  under  the  main  cell  for  starting  and  landing. 
Two  beams  extend  from  the  front  wheel  to  the  engine  bed  and 
serve  to  carry  the  pilot's  seat,  as  will  be  seen  from  the  elevator, 
Fig.  12.  A  third  beam  runs  back  horizontally  from  the  front  wheel 
and  on  rough  ground  acts  as  a  skid.  The  rest  of  the  running  gear  is 
made  of  steel  tubing,  the  pieces  being  joined  simply  by  flattening 
the  ends,  drilling  and  clamping  with  bolts;  no  sockets  or  special 
connections  of  any  kind  are  necessary  here.  If  desired,  the  wheels 
may  be  carried  in  bicycle  forks  and  may  be  fitted  with  shock  absorbers, 
some  idea  of  the  various  expedients  adopted  by  different  builders 
for  this  purpose  being  obtainable  from  the  sketches,  Fig.  40  in  "Types 
of  Aeroplanes."  Two  separate  tubes,  one  on  each  side  of  the  wheel 


593 


28  BUILDING  AND  FLYING  AN  AEROPLANE 

make  a  simple  construction  and  will  probably  serve  just  as  well.  The 
details  of  the  running  gear  will  be  given  later. 

Outrigging  and  Rudders.  For  the  outriggers  and  the  frames 
carrying  the  front  horizontal  or  elevating  rudder  and  the  rear  vertical 
rudder  and  tail,  or  horizontal  keel,  either  spruce  or  bamboo  may  be 
employed.  Bamboo  will  be  found  on.  machines  turned  out  by  the 
Curtiss  factory,  and  while  it  is  the  lighter  of  the  two,  it  is  not  gen- 
erally favored,  as  spruce  is  easier  to  obtain  in  good  quality  and  is 
far  easier  to  work.  At  their  ends,  these  outriggers  are  fitted  with 
ferrules  of  steel  tubing,  flattened  and  drilled  through.  The  out- 
riggers are  attached  to  the  main  framework  of  the  machine  by 
slipping  the  ferrules  over  the  socket  bolts  of  the  middle  section 
struts,  above  and  below  the  beams.  It  is  preferable,  however,  to 
attach  the  rear  outriggers  to  extra  bolts  running  through  the  beams, 
so  that  when  the  machine  is  to  be  housed  the  tail  and  rudder  can  be 
unshipped  and  the  triangular  frames  swung  around  against  the  main 
frame,  considerably  reducing  the  space  required. 

The  tail,  horizontal  and  vertical  rudders,  and  the  ailerons  are 
light  frames  of  wood,  covered  on  both  sides  with  the  same  kind  of 
cloth  as  the  main  planes  or  wings.  These  frames  are  braced  with 
piano  wire  in  such  a  manner  that  no  twisting  strains  can  be  put  on 
them.  The  front  horizontal  rudder,  which  is  of  biplane  construc- 
tion like  the  main  cell,  is  built  up  with  struts  in  the  same  way.  Instead 
of  being  fitted  with  sockets,  however,  the  struts  are  held  by  long 
screws  run  through  the  planes  and  into  their  ends,  passing  through 
the  eyes  of  the  turnbuckles. 

DETAILS  OF  CONSTRUCTION 

Main  Planes  and  Struts.  It  is  preferable  to  begin  with  the 
construction  of  the  main  planes  and  their  struts  and  truss  wires, 
the  ribs  already  described  being  the  first  step. 

The  main  beams  offer  no  special  difficulties.  They  are  ovals 
1J  by  If  inches,  all  6  feet  long  except  the  eight  end  ones,  which 
are  6  feet  2  inches.  The  beams  of  the  central  section  should  be  of 
ash,  or  should  be  thicker  than  the  others.  In  the  latter  case,  they 
must  be  tapered  at  the  ends  so  that  the  clamping  sleeves  will  fit  and 
the  additional  wood  must  be  all  on  the  lower  side,  so  that  the  rib  will 
not  be  thrown  out  of  alignment.  The  spruce  used  for  the  other  beams 


594 


BUILDING  AND  FLYING  AN  AEROPLANE  29 

should  be  reasonably  clear  and  straight  grained,  but  a  small  knot 
or  two  does  not  matter,  provided  it  does  not  come  near  the  ends  of 
the  beam.  The  beams  may  be  cut  to  the  oval  shape  by  the  sawmill 
or  planed  down  by  hand. 

"Fish-shaped"  or  "stream-line"  section,  as  it  is  more  commonly 
termed,  is  used  for  the  struts,  Fig.  15.  It  is  questionable  whether 
this  makes  any  material  difference  in  the  wind  resistance,  but  it  is 
common  practice  to  follow  it  in  order  to  minimize  this  factor.  It  is 
more  important  that  the  struts  be  larger  at  their  centers  than  at  the 
ends,  as  this  strengthens  them  considerably.  At  their  ends  the 
struts  have  ferrules  of  the  1-inch  brass  or  steel  tubing,  and  fit  into 
the  sockets  which  clamp  the  ribs  and  beams  together.  The  material 
is  spruce  but  the  four  central  struts  which  carry  the  engine  bed  should 
either  be  ash  or  of  larger  size,  say  1J  by  3  inches. 

Care  Necessary  to  Get  Planes  Parallel.  The  front  struts  must 
be  longer  than  the  rear  ones  by  the  thickness  of  a  main  rib  at  the 
point  where  the  rear  strut  bolt  passes  through  it,  less  the  thickness 
of  the  rib  ferrule  through  which  the  bolt  of  the  front  strut  must 
pass.  However,  the  first  distance  is  not  really  the  actual  thickness 
of  the  rib,  but  the  distance  between  the  top  of  the  rear  beam  and  the 
bottom  of  the  strut  socket.  In  the  drawings  the  difference  in  length 
between  the  front  and  rear  struts  is  given  as  2  inches,  but  it  is 
preferable  for  the  builder  to  leave  the  rear  struts  rather  long  and  then 
measure  the  actual  distance  when  assembling,  cutting  the  struts  to 
fit.  The  ends  of  the  struts  should  also  be  countersunk  enough  to 
clear  the  head  of  the  socket  bolt. 

One  of  the  items  which  the  builder  can  not  well  escape  buying 
in  finished  form  is  the  strut  sockets.  These  are  cup-shaped  affairs 
of  pressed  steel  which  sell  at  20  cents  each.  Sixteen  of  them  will  be 
required  for  the  main  frame,  and  a  dozen  more  can  advantageously 
be  used  in  the  front  and  rear  controls,  though  for  this  purpose  they 
are  not  absolutely  necessary.  They  can  also  be  obtained  in  a  larger 
oval  size  suitable  for  the  four  central  struts  that  carry  the  en  ine 
bed,  as  well  as  in  the  standard  1-inch  size.  The  bolts  which  project 
through  the  bottom  of  the  sockets  are  ordinary  J-inch  stove  bolts, 
with  their  heads  brazed  to  the  sockets. 

For  the  rear  struts,  where  the  bolt  must  pass  through  the  slant- 
ing main  rib,  it  is  advisable  to  make  angle  washers  to  put  under  the 


595 


30  BUILDING  AND  FLYING  AN  AEROPLANE 

socket  and  also  between  the  beam  and  rib.  These  washers  are  made 
by  sawing  up  a  piece  of  heavy  brass  tubing,  or  a  bar  with  a  J-inch 
hole  drilled  in  its  center,  the  saw  cuts  being  taken  alternately  at 
right  angles  and  at  60  degrees  to  the  axis  of  the  tube. 

The  sleeves  which  clamp  together  the  ends  of  the  beams  are 
made  of  sheet  steel  of  about  20  gauge.  The  steel  is  cut  out  on  the 
pattern  given  in  the  drawing,  Fig.  16,  and  the  ^-inch  bolt  holes 
drilled  in  the  flanges.  The  flanges  are  bent  over  by  clamping  the 
sheet  in  a  vise  along  the  bending  line  and  then  beating  down  with  a 
hammer.  Then  the  sleeves  can  be  bent  into  shape  around  a  stray 
end  of  the  beam  wood.  The  holes  for  the  strut  socket  bolts  should 
not  be  drilled  until  ready  to  assemble.  Ordinarily,  &-inch  stove 
bolts  will  do  to  clamp  the  flanges  together. 

Having  reached  this  stage,  the  amateur  builder  must  now  supply 
himself  with  turnbuckles.  As  already  mentioned,  these  may  either 
be  purchased  or  made  by  hand.  It  is  permissible  to  use  either  one 
or  two  turnbuckles  on  each  wire.  One  is  really  sufficient,  but  two — 
one  at  each  end — add  but  little  weight  and  give  greater  leeway  in 
making  adjustments.  As  there  are  about  115  wires  in  the  machine 
which  need  turnbuckles,  the  number  required  will  be  either  115 
or  230,  depending  upon  the  plan  which  is  followed.  Those  of  the 
turnbuckles  to  be  used  on  the  front  and  rear  controls  and  the  ailerons, 
about  one-fifth  of  the  total  number,  may  be  of  lighter  stock  than  those 
employed  on  wires  which  carry  part  of  the  weight  of  the  machine. 

Making  Turnbuckles  for  the  Truss  Wires.  On  the  supposition 
that  the  builder  will  make  his  own  turnbuckles,  a  simple  form  is 
described  here.  As  will  be  seen  from  Fig.  16,  the  turnbuckles  are 
simply  bicycle  spokes,  with  the  nipple  caught  in  a  loop  of  sheet  steel 
and  the  end  of  the  spoke  itself  twisted  into  an  eye  to  which  the  truss 
wire  can  be  attached.  The  sheet  steel  used  should  be  18  or  16  gauge, 
and  may  be  cut  to  pattern  with  a  heavy  pair  of  tin  snips.  The  spokes 
should  be  ^  inch  over  the  threaded  portion.  The  eye  should  be 
twisted  up  tight  and  brazed  so  that  it  can  not  come  apart.  The 
hole  in  the  middle  of  each  strip  is,  of  course,  drilled  the  same  size 
as  the  spoke  nipple.  The  holes  in  the  ends  are  ^  inch. 

In  the  original  Curtiss  machines,  the  turnbuckles  were  strung 
on  the  socket  bolts  one  after  another,  sometimes  making  a  pack  of 
them  half  an  inch  thick.  A  much  neater  construction  is  shown  in 


596 


BUILDING  AND  FLYING  AN  AEROPLANE  31 

the  drawings,  in  which  the  bolt  pierces  a  single  plate  with  lugs  to 
which  to  make  the  turnbuckles  fast  by  riveting.  The  plates  are  of 
different  shapes,  with  two,  three,  or  four  lugs,  according  to  the 
places  where  they  are  to  be  used.  They  are  cut  from  steel  stock 
-fa  inch  thick,  with  J-inch  holes  for  the  socket  bolts  and  3^  inch,  or 
other  convenient  size,  for  the  rivets  that  fasten  on  the  turnbuckles. 

The  relative  merits  of  cable  and  piano  wire  for  trussing  have 
not  been  thoroughly  threshed  out.  Each  has  its  advantages  and 
disadvantages.  Most  of  the  well-known  builders  use  cable;  yet  if 
the  difference  between  1,000  feet  of  cable  at  2J  cents  per  foot  (the 
price  for  500-foot  spools),  and  8  pounds  of  piano  wire  at  70  cents  a 
pound,  looks  considerable  to  the  amateur  builder,  let  him  by  all 
means  use  the  wire.  The  cable,  if  used,  should  be  the  ^-inch  size, 
which  will  stand  a  load  of  800  pounds;  piano  wire  should  be  24  gauge, 
tested  to  745  pounds.  It  should  be  noted  that  there  is  a  special 
series  of  gauges  for  piano  wire,  known  as  the  music  wire  gauge,  in 
which  the  size  of  the  wire  increases  with  the  gauge  numbers,  instead 
of  the  contrary,  as  is  usual  with  machinery  wire  gauges. 

One  by  no  means  unimportant  advantage  of  the  piano  wire 
is  that  it  is  much  easier  to  fasten  into  the  turnbuckles.  A  small  sleeve 
or  ferrule,  a  J-inch  length  of  |-inch  tubing,  is  first  strung  on  the 
wire.  The  end  of  the  wire  is  then  passed  through  the  turnbuckle 
eye,  bent  up,  thrust  through  the  sleeve,  and  again  bent  down.  When 
the  machine  is  taken  apart,  the  wire  is  not  disconnected  from  the 
eye,  but  instead  the  turnbuckle  spoke  is  unscrewed  from  the  nipple. 
The  shape  of  the  she^t-steel  loop  should  be  such  as  to  hold  the  latter 
in  place.  Cable,  on  the  other  hand,  must  be  cut  with  about  2  inches 
to  spare.  After  being  threaded  through  the  turnbuckle  eye,  the 
end  is  wound  back  tightly  on  itself  and  then  soldered,  to  make  certain 
that  it  can  not  loosen. 

With  a  supply  of  turnbuckles  and  cable  or  piano  wire  at  hand, 
the  builder  may  go  ahead  with  the  main  box-like  structure  or  cell, 
which  should  be  completed  except  for  the  cloth  covering,  and  in 
proper  alignment,  before  taking  up  the  construction  of  the  running 
gear  and  controls. 

Running  Gear.  The  running  gear  of  the  machine  is  built  of 
seamless  steel  tubing,  those  parts  which  carry  the  weight  of  the 
machine  direct  being  of  {-inch  outside  diameter,  16-gauge  tubing, 


597 


32 


BUILDING  AND  FLYING  AN  AEROPLANE 


while  the  others  are  f-inch  outside  diameter,  either  18  or  20  gauge. 
About  25  feet  of  the  heavy  and  45  feet  of  the  light  tubing  will  be 
required,  in  lengths  as  follows:  Heavy,  four  3-foot,  three  4-foot;  light, 
one  6-foot,  two  4-foot  6-inch,  and  seven  4-foot  pieces.  Referring 
to  Fig.  17,  two  diagonal  braces  from  the  rear  beam  to  the  engine 
bed,  the  V-shaped  piece  under  the  front  engine  bed  struts  and  all 
of  the  rear  frame  except  the  horizontal  piece  from  wheel  to  wheel, 
are  of  heavy  tubing.  The  horizontal  in  the  rear  frame,  diagonals 
from  the  rear  wheels  and  the  rear  end  of  the  skid  to  the  front  beam, 
the  two  horizontals  between  the  front  and  rear  beam,  and  the  for- 
ward V  are  of  light  tubing. 

Three  ash  beams  are  used  in  the  running  gear.     Two  of  these 
run  diagonally  from  the  rear  end  of  the  engine  bed  to  the  front  wheel. 


6-0"- 


fl — 


Fig.  17.      Details  of  Curtiss  Running  Gear 

These  are  about  10  feet  long  and  1  by  1J  inches  section.  The  third, 
which  on  rough  ground  acts  as  a  skid,  is  8J  feet  long  and  about  2 
inches  square.  Between  the  points  where  the  tubing  frames  are 
attached  to  it,  the  upper,  corners  may  be  beveled  off  with  a  spoke 
shave  an  inch  or  more  down  each  side.  The  beams  are  attached  to 
the  front  wheel  with  strips  of  steel  stock  1J  inches  wide  and  J  inch 
thick.  The  engine  bed  beams  are  also  ash  about  1  by  If  inches 
section.  Their  rear  ends  are  bolted  to  the  middle  of  the  rear  engine 
bed  struts  and  the  front  ends  may  be  J  inch  higher. 

The  wheels  are  usually  20  by  2  inches,  and  of  the  bicycle  type, 


598 


BUILDING  AND  FLYING  AN  AEROPLANE          33 

but  heavier  and  wider  in  the  hub;  the  tires  are  single  tube.  These 
wheels,  complete  with  tires,  cost  about  $10  each.  This  size  is  used 
on  the  standard  Curtiss  machines,  but  novice  operators,  whose  land- 
ings are  not  quite  as  gentle  as  they  might  be,  find  them  easily  broken. 
Therefore,  it  may  be  more  economical  in  the  end  to  pay  a  little  more 
and  get  heavier  tires — at  least  to  start  with. 

For  working  the  tubing  into  shape,  a  plumber's  blow  torch  is 
almost  indispensable — most  automobilists  will  already  possess  one 
of  these.  The  oval,  flat  variety,  holding  about  one  pint,  is  very  handy 
and  packs  away  easily,  but  on  steady  work  requires  filling  somewhat 
too  frequently.  With  a  dozen  bricks  a  shield  can  be  built  in  front  of 
the  torch  to  protect  the  flame  and  concentrate  the  heat.  Whenever 
it  is  to  be  flattened  and  bent,  the  tubing  should  be  brought  to  a 
bright  red  or  yellow  heat.  Screwing  the  vise  down  on  it  will  then 
flatten  it  quickly  without  hammer  marks.  Where  the  bend  is  to  be 
made  in  the  middle  of  the  piece,  however,  it  may  be  necessary  to 
resort  to  the  hammer  and  anvil. 

It  is  convenient  to  start  with  the  framework  under  the  rear* 
beam.  This  may  be  drawn  accurately  to  full  size  on  the  workshop 
floor,  and  the  tubes  bent  to  fit  the  drawing.  With  this  framework  once 
in  place,  a  definite  starting  point  for  the  remainder  of  the  running  gear 
is  established.  Here  and  in  all  other  places,  when  boring  through 
wood,  the  holes  should  be  drilled  out  full,  and  larger  washers  should 
be  placed  under  the  bolt  head  and  nut.  All  nuts  should  be  provided 
with  some  sort  of  locking  device  The  perspective  drawing,  Fig.  17, 
should  show  the  general  arrangement  clearly  enough  to  enable  the 
builder  to  finish  the  running  gear. 

Outriggers.  Both  the  front  and  rear  control  members,  or 
"outriggers"  as  they  are  termed,  Fig.  12,  may  be  conveniently 
built  up  on  the  central  section  of  the  main  frame,  which,  it  is  assumed, 
has  now  been  fitted  with  the  running  gear. 

The  horizontal  rudder,  or  "elevator,"  is  a  biplane  structure  like 
the  main  cell  of  the  machine,  but  with  fewer  struts;  it  is  carried  in 
front  of  the  main  planes  on  two  A-shaped  frames.  The  vertical 
rudder,  at  the  rear,  is  split  along  the  middle  and  straddles  a  fixed 
horizontal  plane,  or  tail.  This  also  is  carried  on  two  A-shaped 
frames.  Lateral  stability  is  controlled  by  two  auxiliary  planes  or 
ailerons,  one  at  each  side  of  the  machine  and  carried  on  the  two  outer 


599 


34 


BUILDING  AND  FLYING  AN  AEROPLANE 


front  struts.  These  three  control  units — elevator,  tail  and  rudder,  and 
ailerons — will  now  be  taken  up  separately  and  their  construction, 
location  on  the  machine,  and  operation  will  be  described. 

Horizonal  Rudder  or  Elevator.     The  two  planes  of  the  elevator 
are  2  feet  wide  by  5  feet  8  inches  long  and  are  spaced  2  feet  apart, 


RUDDER 


FA/L 


A/LEROft 
Fig.  IS.     Details  of  Rudders  and  Ailerons,  Curtiss  Biplane 

being  held  in  this  position  by  ten  struts.  The  frames  of  the  planes 
are  built  of  spruce  sticks  |  by  1  inch,  each  plane  having  two  sticks 
the  full  length  and  five  evenly  spaced  crosspieces  or  ribs.  These 
are  joined  together  with  squares  of  X-sheet  tin,  as  shown  in  the 
detailed  drawing,  Fig.  18.  With  a  little  experimenting,  paper 
patterns  can  be  made  from  which  the  tin  pieces  can  be  cut  out. 
The  sticks  are  then  nailed  through  the  tin  with  f-inch  brads. 


600 


BUILDING  AND  FLYING  AN  AEROPLANE          35 

It  is  convenient  to  draw  the  frames  out  accurately  on  a  smooth 
wood  floor  and  then  work  over  this  drawing.  The  first  few  brads 
will  hold  the  sticks  in  place.  When  all  the  brads  have  been  driven, 
a  little  drop  of  solder  should  be  run  in  around  the  head  of  each  one. 
This  is  a  tedious  job.  One  must  be  careful  to  use  no  more  solder  than 
necessary  as  it  increases  the  weight  very  rapidly.  Two  pounds  of 
wire  solder  should  be  sufficient  for  all  the  control  members  which  are 
built  in  this  way.  When  the  top  side  is  soldered,  pry  the  frame  loose 
from  the  floor  with  a  screwdriver  and  turn  it  over.  Then  the  pro- 
jecting points  of  the  brads  must  be  clinched  and  the  soldering  repeated. 

At  this  stage,  the  two  frames  should  be  covered  on  both  sides 
with  the  prepared  cloth  used  for  covering  the  main  planes.  The 
method  of  preparing  this  cloth  is  detailed  a  little  farther  along. 

The  struts,  so-called,  to  continue  the  analogy  with  the  main 
planes,  are  turned  sticks  of  spruce  f  inch  in  diameter.  They  are 
fitted  at  each  end  with  ferrules  of  thin  f-inch  brass,  or  steel  tubing, 
driven  on  tight.  Instead  of  using  sockets,  the  struts  are  held  at  each 
end,  simply  by  a  long  wood  screw  driven  through  the  tin  and  wood 
of  the  plane  frame  and  into  the  strut.  These  screws  also  hold  the 
turnbuckles  for  the  truss  wires.  For  trussing  purposes,  the  elevator 
is  regarded  as  consisting  of  two  sections  only,  the  intermediate  struts 
being  disregarded. 

The  turnbuckles  and  wire  used  here  and  in  the  other  control 
members  may  well  be  of  lighter  stock  than  those  used  in  the  main 
planes.  Piano  wire,  Xo.  18,  or  t^-inch  cable  is  amply  strong.  The 
sheet  steel  may  be  (about  22  gauge,  instead  of  1G,  and  the  bicycle 
spokes  smaller  in  proportion.  No  turnbuckle  plates  are  necessary. 
The  screws  running  into  the  struts  may  be  passed  directly  through 
the  eyes  of  the  turnbuckles,  where  they  would  have  been  attached 
to  the  turnbuckle  plate.  In  order  to  secure  a  square  and  neat  struc- 
ture, those  struts  which  have  turnbuckles  at  their  ends  should  be 
made  a  trifle  shorter  than  the  others. 

At  each  end,  the  elevator  has  an  X-shaped  frame  of  J-inch  steel 
tubing;  at  the  intersection  of  the  X's  are  pivots  on  which  the  elevator 
is  supported.  Each  X  is  made  of  two  tubes,  bent  into  a  V  and  flat- 
tened and  brazed  together  at  the  points.  The  ends  of  the  X's  are 
flattened  and  bent  over  so  that  the  screws  which  hold  the  struts 
in  place  may  pass  through  them. 


601 


36 


BUILDING  AND  FLYING  AN  AEROPLANE 


To  the  front  middle 
strut  is  attached  an  exten- 
sion which  acts  as  a  lever 
for  operating  the  elevator. 
This  is  a  stick  of  spruce  f 
inch  in  diameter  and  3  feet 
3  inches  long.  At  its  upper 
end  it  has  a  ferrule  of  steel 
tubing,  flattened  at  the 
end.  The  lower  part  of 
the  stick  may  be  fastened 
to  the  strut  by  wrapping 
the  tube  with  friction  tape, 
or  by  improvising  a  couple 
of  sheet  steel  clamps.  The 
upper  end  of  the  stick  is 
braced  by  a  J-inch  steel 
tube,  extending  to  the  top 
of  the  rear  middle  strut, 
and  held  by  the  same 
screw  as  the  strut.  This 
extension  lever  is  connect- 
ed to  the  steering  column 
by  a  bamboo  rod,  1  inch 
in  diameter  and  about  10 
feet  long,  provided  with 
flattened  ferrules  of  steel 
tubing  at  each  end.  Each 
ferrule  should  be  held  on 
by  a  J-in(*h  stove  bolt  pass- 
ing through  it. 

Front  and  Rear  Outrigger 
Frames.  Both  the  front 
elevator  and  the  tail  and 
rudder  at  the  rear,  are  car- 
ried, as  mentioned  above, 
each  on  a  pair  of  A-shaped 
frames,  similar  to  one  an- 


602 


BUILDING  AND  FLYING  AN  AEROPLANE 


37 


other,  except  that  those  in  the  rear  are  longer  than  those  in  the 
front.  Both  are  made  of  spruce  of  about  the  same  section  as  used 
for  the  struts  of  the  main  frame.  These  pieces  may  either  be  full 
length,  or  they  may  be  jointed  at  the  intersection  of  the  crosspieces, 
the  ends  being  clamped  in  a  sheet-steel  sleeve,  just  like  that  used 
on  the  beams  of  the  main  frame.  In  this  case,  it  is  advisable  to 
run  a  J-inch  stove  bolt  through  each  of  the  ends. 


Fig.  20.     Details  of  Outriggers  and  Front  Elevating  Planes  as  Seen  from  Driver's  Seat 

The  crosspieces  of  the  A-frames  are  spruce  of  the  same  section, 
or  a  little  smaller.  At  their  ends  may  be  used  strut  sockets  like  those 
of  the  main  frame;  or,  if  it  is  desired  to  save  this  expense,  they  may 
be  fastened  by  strips  of  ^-inch  steel  stock  with  through  bolts. 

The  front  outrigger  has,  besides  the  two  A-frames,  a  rather  com- 
plicated arrangement  of  struts  designed  to  brace  the  front  wheel 


603 


38  BUILDING  AND  FLYING  AN  AEROPLANE 

against  the  shocks  of  landing.  This  arrangement  does  not  appear 
very  plain  in  a  plan  or  elevation,  and  may  best  be  understood  by 
reference  to  the  photograph,  Fig.  19,  and  the  perspective  drawing, 
Fig.  20.  Fig.  20  is  a  view  from  the  driver's  seat.  The  elevator  is 
seen  in  front,  the  A-frames  at  each  side,  and  at  the  bottom  the  two 
diagonal  beams  to  the  engine  bed  and  the  skid. 

Reference  to  this  drawing  will  show  the  two  diagonals  run  from 
the  front  wheel  up  and  back  to  the  top  of  the  main  frame,  and  two 
more  from  the  wheel  forward  to  the  short  crosspieces  near  the  apexes 
of  the  A-frame:  there  is  also  a  vertical  strut  which  intersects  two 
horizontal  pieces  running  between  the  ends  of  the  longer  crosspieces 
of  the  A-frames.  Altogether,  there  are  five  attachments  on  each  side 
of  the  front  wheel,  through  which  the  axle  bolt  must  pass,  viz,  the 
connections  to  the  skid,  to  one  of  the  diagonals  to  the  engine  bed, 
to  one  of  the  rear  diagonals,  to  one  of  the  front  diagonals,  and  to  one 
side  of  the  fork  carrying  the  vertical  strut.  Of  these  the  skid  attach- 
ments should  be  on  the  inside  closest  to  the  wheel,  and  the  engine 
bed  diagonals  next. 

The  four  additional  diagonals  running  to  the  front  wheel  may 
be  spruce  of  the  same  section  used  in  the  A-frames,  or  turned  one 
inch  round.  At  each  end  they  have  flattened  ferrules  of  steel  tubing. 
The  beams  of  the  A-frames  have  similar  ferrules  at  the  ends  where 
they  attach  to  the  main  frames.  These  attachments  should  be  made 
on  the  socket  bolts  of  the  struts  on  either  side  of  the  middle  6-foot 
section  and  on  the  outer  side  of  the  main  beams — not  between  the 
beam  and  the  socket  itself. 

It  is  possible,  of  course,  to  make  all  the  A-frames  and  diagonal 
braces  of  bamboo,  if  desired,  the  qualities  of  this  material  already 
having  been  referred  to.  Bamboo  rods  for  this  purpose  should  be 
between  1  and  1J  inches  in  diameter.  Where  ferrules  are  fitted  on 
the  ends,  the  hole  of  the  bamboo  should  be  plugged  with  wood  glued 
in  place. 

Generally,  in  the  construction  of  the  outrigger  frames,  the 
builder  can  use  his  own  discretion  to  a  considerable  extent.  There 
are  innumerable  details  which  can  be  varied — far  too  many  to  con- 
sider even  a  part  of  the  possibilities  in  this  connection.  If  the  builder 
runs  across  any  detail  which  he  does  not  see  mentioned  here,  he  may 
safely  assume  that  any  workmanlike  job  will  suffice.  Often,  the 


604 


BUILDING  AND  FLYING  AN  AEROPLANE  39 

method  may  be  adapted  to  the  materials  on  hand.  The  diagonal 
wires  from  the  crosspieces  of  the  A-frames  to  the  struts  should  be 
crossed. 

Rudder  and  Tail  Construction.  The  frame  for  the  rudder  and 
tail  are  constructed  in  much  the  same  way  as  those  for  the  elevator, 
Fig.  18.  Spruce  sticks  1  by  \  inch  are  used  throughout,  except  for 
the  piece  at  the  back  edge  of  the  rudder  and  the  long  middle  piece 
across  the  tail;  these  should  be  \\  by  \  inch.  This  long  middle  piece 
of  the  tail  is  laid  across  on  top  of  the  rest  of  the  framework.  When 
the  cloth  is  put  on,  this  makes  the  upper  surface  slightly  convex  while 
the  lower  surface  remains  flat.  The  ends  of  this  piece  should  be 
reinforced  with  sheet  steel,  fairly  heavy  and  drilled  for  J-inch  bolts, 
attaching  the  tail  to  the  A-frames. 

The  rudder  is  hung  from  two  posts  extending  above  and  below 
the  tail.  These  posts  may  be  set  in  cast  aluminum  sockets,  such  as 
may  be  obtained  from  any  supply  house  for  20  cents  apiece.  The 
posts  need  not  be  more  than  f  inch  in  diameter.  At  their  outer  ends, 
they  should  have  ferrules  of  steel  tubing,  and  the  turnbuckles  or  other 
attachments  for  the  truss  wires  should  be  attached  by  a  wood  screw 
running  into  the  end  of  each.  From  these  posts  the  rudder  may  be 
hung  on  any  light  hinges  the  builder  may  find  convenient,  or  on 
hinges  improvised  from  screw  eyes  or  eye  bolts,  with  a  bolt  passing 
through  the  eyes  of  each. 

In  steering,  the  rudder  is  controlled  by  a  steering  wheel  carried 
on  a  hinged  post  in  front  of  the  pilot.  This  post  should  be  ash  about 
1  by  1J  inches.  It  (hinges  at  the  bottom  on  a  steel  tube  of  ^-inch 
diameter  which  passes  through  it  and  is  supported  at  the  ends  on 
diagonal  beams  to  the  engine  bed.  Two  diagonals  of  lighter  tubing 
may  be  put  in  to  hold  the  posts  centered  between  the  two  beams. 

The  post  is,  of  course,  upright,  and  the  hub  of  the  wheel  is 
horizontal.  The  wheel  may  be  conveniently  mounted  on  a  piece  of 
tubing  of  the  same  size  as  the  hub  hole,  run  through  the  post  and 
held  by  a  comparatively  small  bolt,  which  passes  through  it  and  has 
a  big  washer  on  either  end.  The  wheel  is  preferably  of  the  motor- 
boat  variety  with  a  groove  around  the  rim  for  the  steering  cable. 

The  rear  edge  of  the  tail  should  be  about  1  inch  lower  than  the 
front.  To  make  the  rudder  post  stand  approximately  vertical, 
wedge-shaped  pieces  of  wood  may  be  set  under  the  sockets. 


605 


40  BUILDING  AND  FLYING  AN  AEROPLANE 

The  steering  connections  should  be  of  flexible  cables  of  steel 
such  as  are  made  for  this  purpose.  There  should  be  a  double  pulley 
on  the  post  just  under  the  wheel,  and  the  cables  should  be  led  off 
the  post  just  at  the  hinge  at  the  bottom,  so  that  swinging  the  post 
will  not  affect  them.  The  cable  is  then  carried  under  the  lower  main 
plane  and  out  the  lower  beams  of  the  A-frames.  It  is  attached  to 
the  rudder  at  the  back  edge;  snap  hooks  should  be  used  for  easy 
disconnection  in  packing.  Perhaps  the  best  way  of  guiding  the  cable, 
instead  of  using  pulleys,  is  to  run  it  through  short  pieces  of  tubing 
lashed  to  the  beams  with  friction  tape.  The  tubing  can  be  bent 
without  flattening  by  first  filling  it  with  melted  lead,  which,  after 
the  bending,  can  be  melted  out  again. 

Ailerons  for  Lateral  Stability.  The  framework  of  the  ailerons 
is  made  in  the  same  way  as  that  for  the  elevator,  tail,  and  rudder, 
Fig.  18.  The  pieces  around  the  edges  should  be  1J  by  J  inch,  as 
also  the  long  strip  laid  over  the  top  of  the  ribs.  The  ribs  should  be 
J  by  f  inch.  Each  aileron  has  two  holes,  one  for  the  strut  to  pass 
through,  and  the  other  for  the  diagonal  truss  wires  at  their  inter- 
section. The  back  edge  also  has  a  notch  in  it  to  clear  the  fore  and 
aft  wires.  Each  aileron  is  hung  on  four  strips  of  soft  steel  about  \ 
by  iV  inch,  twisted  so  that  one  end  is  at  right  angles  to  the  other. 
These  are  arranged  one  on  each  side  of  the  strut  which  passes  through 
the  aileron,  and  one  at  each  end.  Bolts  through  the  struts  carry  three 
of  them  and  the  outer  one  is  trussed  by  wires  to  each  end  of  the  outer 
strut. 

A  frame  of  J-inch  steel  tubing  fits  around  the  aviator's  shoulders 
and  is  hinged  to  the  seat,  so  that  he  can  move  it  by  leaning  from  one 
side  to  the  other.  This  is  connected  by  flexible  cable  to  the  rear 
edges  of  the  ailerons,  so  that  when  the  aviator  leans  to  the  left,  he 
will  raise  the  left  and  lower  the  right  aileron.  The  upper  edges  of 
the  ailerons  are  directly  connected  to  each  other  by  a  cable  running 
along  the  upper  front  beam,  so  that  they  must  always  move  together. 

Covering  of  the  Planes.  Mention  has  already  been  made  of 
the  fact,  in  the  general  description  of  the  machine,  that  light  sail 
cloth,  as  employed  on  the  Wright  machines,  may  be  used  for  the 
planes  or  wings.  As  a  matter  of  fact,  many  different  materials  may 
be  successfully  employed,  the  selection  depending  upon  the  builder 
himself  and  his  financial  resources.  About  55  square  yards  of  material 


606 


BUILDING  AND  FLYING  AN  AEROPLANE  41 

will  be  required,  and  in  comparing  prices  always  compare  the  width 
as  this  may  vary  from  28  to  55  inches.  Rubberized  silk  which  is  used 
on  the  standard  Curtiss  machines  is  the  most  expensive  covering, 
its  cost  running  up  to  something  like  two  hundred  dollars.  There 
are  also  several  good  aero  fabrics  on  the  market  which  sell  at  60 
cents  a  square  yard,  as  well  as  a  number  of  brands  of  varnish  for  the 
cloth — most  of  them,  however,  quite  expensive.  The  most  economical 
method  is  to  employ  a  strong  linen  cloth  coated  with  shellac,  which 
will  be  found  very  satisfactory. 

The  covering  of  the  frames  with  the  cloth  may  well  be  post- 
poned until  after  the  engine  has  been  installed  and  tested,  thus  avoid- 
ing the  splashing  of  oil  and  dirt  which  the  fabric  is  apt  to  receive 
during  this  operation.  The  wire  to  which  the  cloth  is  laced,  must 
be  strung  along  the  rear  ends  of  the  ribs  of  each  plane.  The  wires 
pass  through  holes  in  the  ends  of  the  small  ribs  and  are  attached 
to  the  main  ribs  with  turnbuckles.  At  the  ends  of  the  planes  the 
main  ribs  must  be  braced  against  the  pull  of  the  wire  by  a  piece  of 
J-inch  tubing  running  from  the  end  of  the  rib  diagonally  up  to  the 
rear  beam.  Both  turnbuckles  and  tube  are  fastened  with  one  wood 
screw  running  into  the  end  of  the  rib. 

The  cloth  should  be  cut  to  fit  the  panels  between  the  main 
ribs  and  hemmed  up,  allowing  at  least  an  inch  in  each  direction  for 
stretch.  Small  eyelets  should  be  put  along  the  sides  and  rear  edges 
an  inch  apart  for  the  lacing.  At  the  front  edge,  the  cloth  is  tacked 
directly  to  the  beam,  the  edge  being  taken  well  under  and  around 
to  the  back.  Strongmsh  line  is  good  material  for  the  lacing. 

After  the  cloth  is  laced  on,  it  must  be  tacked  down  to  the  small 
ribs.  For  this  purpose,  use  upholstery  tacks  as  they  have  big  cup- 
shaped  heads  which  grip  the  cloth  and  do  not  tear  out.  As  an  extra 
precaution  a  strip  of  heavy  tape  must  be  run  over  each  rib  under 
the  tack  heads.  All  the  control  members  are  covered  on  both  sides, 
the  edges  being  folded  under  and  held  by  tacks. 

Making  the  Propeller.  If  the  completed  biplane  is  to  fly 
properly  and  also  have  sufficient  speed  to  make  it  safe,  consider- 
able care  must  be  devoted  to  the  design  and  making  of  the  pro- 
peller. Every  aeroplane  has  a  safe  speed,  usually  referred  to  in 
technical  parlance  as  its  critical  speed.  In  the  case  of  the  Curtiss 
biplane  under  consideration,  this  speed  is  about  40  miles  an  hour. 


607 


42  BUILDING  AND  FLYING  AN  AEROPLANE 

By  speeding  up  the  motor  considerably,  it  may  be  able  to  make 
42  to  43  miles  an  hour  in  a  calm,  such  a  condition  representing  the 
only  true  measure  of  an  aeroplane's  ability  in  this  direction,  while 
on  the  other  hand,  it  would  not  be  safe  to  let  its  speed  with  relation 
to  the  wind  (not  to  the  ground)  fall  much  below  35  miles  an  hour. 
At  any  slower  rate  of  travel,  its  dynamic  stability  would  be  pre- 
carious and  the  machine  would  be  likely  to  dive  to  the  ground  unex- 
pectedly. The  reasons  for  this  have  been  explained  more  in  detail 
under  the  heading  of  "The  Internal  Work  of  the  Wind." 

The  necessity  of  making  the  propeller  need  not  discourage  the 
ambitious  builder — if  he  can  spare  the  time  to  do  it  right,  it  will 
be  excellent  experience.  If  not,  propellers  designed  for  driving  a 
machine  of  this  size  can  be  purchased  ready  to  mount  from  any  one 
of  quite  a  number  of  manufacturers.  But  as  the  outlay  required 
will  be  at  least  $50,  doubtless  most  experimenters  will  prefer  to 
undertake  this  part  of  the  work  as  well  as  that  of  building  the  frame- 
work and  main  cell,  particularly  as  more  than  90  per  cent  of  the 
sum  mentioned  is  represented  by  labor.  The  cost  of  the  material 
required  is  insignificant  by  comparison. 

True-Screw  Design.  First  it  will  be  necessary  to  design  the 
propeller  to  meet  the  requirements  of  the  biplane  itself.  As  this  is 
a  matter  that  has  already  been  gone  into  in  considerable  detail 
under  the  appropriate  heading,  no  further  explanation  of  propeller 
characteristics  or  of  the  technical  terms  employed,  should  be  needed 
here.  We  will  assume  that  the  biplane  is  to  have  a  speed  of  40  miles 
per  hour  in  still  air  with  the  motor  running  at  1,200  r.  p.  m.  With 
this  data,  it  will  not  be  difficult  to  calculate  the  correct  pitch  of  the 
propeller  to  give  that  result.  Thus 

40X5280X100_ 
60X1200X  85  ~ 

or  in  round  numbers  a  pitch  of  3|  feet.  40  (the  speed  in  miles  per 
hour)  times  5,280  (feet  per  mile)  divided  by  60  (minutes  in  an  hour) 
gives  the  speed  of  the  aeroplane  in  feet  per  minute.  Dividing  this  by 
1,200  (revolutions  per  minute)  gives  the  number  of  feet  the  aeroplane 
is  to  advance  per  revolution  of  the  propeller.  The  "-8™"  part  of 
the  equation  represents  the  efficiency  of  the  propeller  which  can 
safely  be  figured  on,  i.  c.,  85  per  cent,  or  an  allowance  for  slip  of  15 


608 


BUILDING  AND  FLYING  AN  AEROPLANE  43 

per  cent.  Forty  miles  an  hour  is  the  maximum  speed  to  be  expected, 
while  the  r.  p.  m.  rate  of  the  engine  should  be  that  at  which  it  operates 
to  the  best  advantage. 

The  merits  of  the  true-screw  and  variable-pitch  propellers  have 
already  been  dwelt  upon.  The  former  is  not  only  more  simple  to 
build,  but  experience  has  shown  that,  as  generally  employed,  it 
gives  better  efficiency.  Hence,  the  propeller  under  consideration 
will  be  of  the  true-screw  type.  Its  pitch  has  already  been  calculated 
as  3J  feet.  For  a  machine  of  this  size  and  power,  it  should  be  6  feet 
in  diameter.  Having  worked  out  the  pitch  and  decided  upon  the 
diameter,  the  next  and  most  important  thing  is  to  calculate  the  pitch 
angle.  It  will  be  evident  that  no  two  points  on  the  blatie  will  travel 
through  the  air  at  the  same  speed.  Obviously,  a  point  near  the  tip 
of  the  propeller  moves  faster  than  one  near  the  hub,  just  as  in  round- 
ing a  curve,  the  outer  wheel  of  an  automobile  has  to  travel  faster 
than  the  inner,  because  it  has  to  travel  farther  to  cover  the  same 
ground.  For  instance,  taking  the  dimensions  of  the  propeller  in 
question  it  will  be  seen  that  its  tips  will  be  traveling  through  the  air 
at  close  to  4.3  miles  per  minute,  that  is, 


5280 

in  which  6,  the  diameter  of  the  propeller  m  feet,  times  K  gives  the 
circumference  of  the  circle  which  is  traveled  by  the  blade  tips  1,200 
times  per  minute;  this  divided  by  the  number  of  feet  per  mile  gives 
the  miles  per  miniite  covered.  On  the  other  hand,  a  point  on  the 
blade  but  6  inches  from  the  hub  will  turn  at  only  approximately 
3,500  feet  per  minute.  Therefore,  if  every  part  of  the  blade  is  to 
advance  through  the  air  equally,  the  inner  part  must  be  set  at  a 
greater  angle  than  the  outer  part.  Each  part  of  the  blade  must  be 
set  at  such  an  angle  that  at  each  revolution  it  will  move  forward 
through  the  air  a  distance  equal  to  the  pitch.  This  is  known  as  the 
pitch  angle.  The  pitch  divided  by  the  circumference  of  the  circle 
described  by  any  part  of  the  blade,  will  give  a  quantity  known  as 
the  tangent  of  an  angle  for  that  particular  part.  The  angle  corre- 
sponding to  that  tangent  may  most  easily  be  found  by  referring  to 
a  book  of  trigonometric  tables. 

For  example,  take  that  part  of  the  blade  of  a  3J-foot  pitch  pro- 


609 


44 


BUILDING  AND  FLYING  AN  AEROPLANE 


TABLE  II 
Propeller  Blade  Data 


Radius  in 
Inches 

Tangent 

Pitch  Angle 

Add 

Final  Angle 

6 

1.1141 

48°     5' 

48° 

9 

.7427 

36°  36' 

37° 

12 

.5571 

29°     7' 

3°  13' 

32°  20' 

15 

.4457 

24°     1' 

3°    9' 

27°  10' 

18 

.3719 

20°  24' 

3°    6' 

23°  30' 

21 

.3183 

17°  40' 

3° 

20°  40' 

24 

.2785 

15°  40' 

2°  50' 

18°  30' 

27 

.2476 

13°  54' 

2°  46' 

16°  40' 

30 

.2228 

12°  40' 

2°  45' 

15°  25' 

33 

.2025 

11°  27' 

2°  43' 

14°  10' 

peller  which  is  6  inches  from  the  center  of  the  hub.    Then 

3  5X 1^ 

-"=1.1141  tangent  of  48  degrees  5  minutes 
6X27T 

in  which  3.5X12  reduces  the  pitch  to  inches,  while  6X2?r  is  the 
circumference  of  the  circle  described  by  the  point  6  inches  from  the 
hub.  However,  in  order  to  give  the  propeller  blade  a  proper  hold 
on  the  air,  it  must  be  set  at  a  greater  angle  than  these  figures  would 
indicate.  That  is,  it  must  be  given  an  angle  of  incidence  similar  to 
that  given  to  every  one  of  the  supporting  planes  of  the  machine. 
This  additional  angle  ranges  from  2  degrees  30  minutes,  to  4  degrees, 
depending  upon  the  speed  at  which  the  particular  part  of  the  blade 
travels;  the  greater  the  speed,  the  less  the  angle.  This  does  not  apply 
to  that  part  of  the  blade  near  the  hub  as  the  latter  is  depended  upon 
solely  for  strength  and  is  not  expected  to  add  to  the  effective  thrust 
of  the  propeller. 

Table  II  shows  the  complete  set  of  figures  for  a  blade  of  3J-foot 
pitch,  the  angles  being  worked  out  for  sections  of  the  blade  3  inches 
apart. 

These  angles  are  employed  in  Fig.  21,  which  shows  one  blade 
of  the  propeller  and  its  cross  sections. 

It  should  be  understood  that  these  calculations  apply  only  to 
the  type  of  propeller  known  as  the  true  screw,  as  distinguished  from 
the  variable  pitch.  The  design  of  the  latter  is  a  matter  of  personal 
skill  and  experience  in  its  making  which  is  hardly  capable  of 


610 


Fig.  21.     Details  of  Propeller  Construction,  Curtiss  Biplane 


611 


46          BUILDING  AND  FLYING  AN  AEROPLANE 

expression  in  any  mathematical  formula.  There  are  said  to  be  only 
about  three  men  in  this  country  who  know  how  to  make  a  proper 
variable-pitch  propeller,  and  it  naturally  is  without  advantage  when 
made  otherwise. 

Shaping  the  Blades.  Like  the  ribs,  the  propeller  is  made  up 
of  a  number  of  laminations  of  boards  finished  true  and  securely 
glued,  afterward  being  cut  to  the  proper  shape,  though  this  process, 
of  course,  involves  far  more  skill  than  in  the  former  case.  Spruce  is 
the  strongest  wood  for  its  weight,  but  it  is  soft  and  cracks  easily. 
Maple,  on  the  other  hand,  is  tough  and  hard,  so  that  it  will  be  an 
advantage  to  alternate  the  layers  of  these  woods  with  an  extra 
maple  board,  in  order  to  make  both  outside  strips  of  the  harder 
wood,  so  as  to  form  a  good  backing  for  the  steel  flanges  at  the  hub, 
the  rear  layer  extending  the  full  length  of  the  thin  rear  edges  of  the 
blades.  Other  woods  may  be  employed  and  frequently  are  used  by 
propeller  manufacturers,  such  as  mahogany  (not  the  grained  wood 
used  for  furniture,  but  a  cheaper  grade  which  is  much  stronger), 
walnut,  alternate  spruce  and  whitewood,  and  others. 

The  boards  should  be  selected  with  the  greatest  care  so  as  to 
insure  their  being  perfectly  clear,  i.e.,  absolutely  free  of  knots, 
cross-grained  streaks,  or  similar  flaws,  which  would  impair  their 
strength  and  render  them  difficult  to  work  smoothly.  They  should 
measure  6  inches  wide  by  6  feet  1  inch  in  length.  Their  surfaces 
must  be  finished  perfectly  true,  so  that  they  will  come  together 
uniformly  all  over  the  area  on  which  they  bear  on  one  another,  and 
the  various  pieces  must  be  glued  together  with  the  most  painstaking 
care.  Have  the  glue  hot,  so  that  it  will  spread  evenly,  and  see  that 
it  is  of  a  uniform  consistency,  in  order  that  it  may  be  smoothly 
applied  to  every  bit  of  the  surface.  They  must  then  be  clamped 
together  under  as  much  pressure  as  it  is  possible  to  apply  to  them 
with  the  means  at  hand,  the  rib  press  already  described  in  detail 
forming  an  excellent  tool  for  this  purpose.  Tighten  up  the  nuts 
evenly  a  little  at  a  time,  avoiding  the  application  of  excessive  or 
uneven  pressure  at  one  point,  continuing  the  gradual  tightening  up 
process  until  it  can  not  be  carried  any  farther.  This  is  to  prevent  the 
boards  from  assuming  a  curve  in  drying  fast.  Allow  at  least  twenty- 
four  hours  for  drying,  during  which  period  the  laminated  block  should 
be  kept  in  a  cool,  dry  place  at  as  even  a  temperature  as  possible. 


612 


BUILDING  AND  FLYING  AN  AEROPLANE          47 

Before  undertaking  the  remainder  of  the  work,  all  of  which 
must  be  carried  out  by  hand,  with  the  exception  of  cutting  the 
block  to  the  outline  of  the  propeller,  which  may  be  done  with  a  band 
saw,  a  set  of  templates  or  gauges  should  be  made  from  the  drawings. 
These  will  be  necessary  as  guides  for  finishing  the  propeller  acurately. 
Draw  the  sections  out  full  size  on  sheets  of  cardboard  or  tin  and 
cut  out  along  the  curves,  finally  dividing  each  sheet  into  two  parts, 
one  for  the  upper  side  and  one  for  the  lower.  Care  must  be  taken 
to  get  the  sides  of  the  template  square,  and  when  they  are  used,  the 
propeller  should  be  laid  on  a  perfectly  true  and  flat  block.  Each 
template  should  be  marked  as  it  is  finished,  to  indicate  what  part 
of  the  blade  it  is  a  gauge  for.  The  work  of  cutting  the  laminated 
block  down  to  the  lines  represented  by  the  templates  is  carried  out 
with  the  aid  of  the  plane,  spoke  shave,  and  gouge.  After  the  first 
roughing  out  to  approximate  the  curvature  of  the  finished  propeller 
is  completed,  the  cuts  taken  should  be  very  fine,  as  it  will  be  an  easy 
matter  to  go  too  deep,  thus  spoiling  the  block  and  necessitating  a 
new  start  with  fresh  material.  For  finishing,  pieces  of  broken  glass 
are  employed  to  scrape  the  wood  to  a  smooth  surface,  followed  by 
coarse  and  finally  by  fine  sandpaper. 

Mounting.  The  hub  should  be  of  the  same  diameter  as  the 
flange  on  the  engine  crank  shaft  to  which  the  flywheel  was  bolted, 
and  should  have  its  bolt  holes  drilled  to  correspond.  To  strengthen 
the  hub,  light  steel  plates  of  the  same  diameter  are  screwed  to  it, 
front  and  back,  and  the  bolt  holes  drilled  right  through  the  metal 
and  wood.  This  method  of  fastening  is  recommended  where  it  is 
possible  to  substitute  the  propeller  for  the  flywheel  formerly  on  the 
engine,  it  being  common  practice  to  omit  the  use  of  the  flywheel 
altogether.  The  writer  does  not  recommend  this,  however,  as  the 
advantages  of  smoother  running  and  more  reliable  operation  gained 
by  the  use  of  a  flywheel  in  addition  to  the  propeller  far  more  than 
offset  any  disadvantage  represented  by  its  weight.  It  will  be  noted 
that  the  Wright  motors  have  always  been  equipped  with  a  flywheel 
of  ample  size  and  weight  and  this  is  undoubtedly  responsible,  in  some 
measure  at  least,  for  the  fact  that  the  Wright  biplanes  fly  with  con- 
siderably less  power  than  is  ordinarily  employed  for  machines  of 
the  same  size.  If  the  motor  selected  be  equipped  with  an  unusually 
heavy  flywheel,  and  particularly  where  the  wheel  is  of  comparatively 


613 


48  BUILDING  AND  FLYING  AN  AEROPLANE 

small  diameter,  making  it  less  effective  as  a  balancer,  it  may  be 
replaced  with  one  of  lighter  weight  and  larger  diameter.  It  may  be 
possible  to  attach  it  by  keying  to  the  forward  end  of  the  crank  shaft, 
thus  leaving  the  flange  from  which  the  flywheel  was  taken  free  for 
mounting  the  propeller.  An  ordinary  belt  pulley  will  serve  excel- 
lently as  the  new  flywheel,  as  most  of  its  weight  is  centered  in  its  rim, 
but  as  the  common  cast-iron  belt  pulley  of  commerce  is  seldom 
intended  to  run  at  any  such  speed  as  that  of  an  automobile  motor, 
it  should  be  examined  carefully  for  flaws.  Otherwise,  there  will  be 
danger  of  its  bursting  with  disastrous  results  under  the  influence  of 
centrifugal  force.  Its  diameter  should  not  exceed  16  inches  in  order 
to  keep  its  peripheral  speed  within  reasonable  limits.  Wl  ere  the 
mounting  of  the  motor  permits  of  its  use,  a  wood  pulley  18  to  20 
inches  in  diameter  with  a  steel  band  about  f-  to  J-inch  thick,  shrunk 
on  its  periphery,  may  be  employed.  Most  builders  will  ridicule  the 
idea  of  a  flywheel  other  than  the  propeller  itself.  "You  do  not  need 
it;  so  why  carry  the  extra  weight?"  will  be  their  query.  It  is  not 
absolutely  necessary,  but  it  is  an  advantage. 

In  case  the  flywheel  of  the  engine  selected  is  keyed  to  the  crank 
shaft,  or  in  case  it  is  not  possible  to  mount  both  the  flywheel  and 
the  propeller  on  different  ends  of  the  crank  shaft,  some  other  expedient 
rather  than  that  of  bolting  to  the  flange  must  be  adopted.  In  such 
a  case,  the  original  flywheel,  where  practical  to  retain  it,  may  be 
drilled  and  tapped  and  the  propeller  attached  directly  to  it.  Where 
the  flywheel  can  not  be  kept,  it  will  usually  be  found  practical  to 
cut  off  its  rim  and  bolt  the  propeller  either  to  the  web  or  spokes,  or 
to  the  flywheel  hub,  if  it  be  cut  down  to  the  latter. 

The  drawing,  Fig.  21,  shows  the  rear  or  concave  side  of  the 
propeller.  From  the  viewpoint  of  a  man  standing  in  its  wind  and 
facing  forward,  it  turns  to  the  left,  or  anti-clockwise.  On  many  of 
the  propellers  now  on  the  market,  the  curved  edge  is  designed  to  go 
first.  This  type  may  have  greater  advantages  over  that  described, 
but  the  straight  front  edge  propeller  is  easier  for  the  amateur  to 
make. 

Mounting  the  Engine.  Having  completed  the  propeller,  the 
next  step  is  the  mounting  of  the  engine.  Reference  to  the  types 
available  to  the  amateur  aeroplane  builder  has  already  been  made. 
There  are  a  number  of  motors  now  on  the  market  that  have  been 


614 


BUILDING  AND  FLYING  AN  AEROPLANE          49 

designed  specially  for  this  purpose  and  not  a  few  of  them  are  of  con- 
siderable merit.  Their  cost  ranges  from  about  $250  up  to  $2,500, 
but  it  may  be  possible  to  pick  up  a  comparatively  light-weight 
automobile  motor  second  hand  which  will  serve  all  purposes  and 
which  will  cost  far  less  than  the  cheapest  aeronautic  motor  on  the 
market.  It  must  be  capable  of  developing  30  actual  horse-power 
at  1,000  to  1,200  r.  p.  m.  and  must  not  exceed  400  pounds  complete 
with  all  accessories,  such  as  the  radiator  and  piping,  magneto,  water, 
oil,  etc.  Considerable  weight  may  be  saved  on  an  automobile  motor 
by  removing  the  exhaust  manifold  and  substituting  a  lighter  flywheel 
for  the  one  originally  on  the  engine — or  omitting  it  altogether,  as 
just  mentioned.  A  light-weight  aeronautic  radiator  should  be  used 
in  preference  to  the  usual  automobile  radiator. 

When  placing  the  engine  in  position  on  the  ash  beams  forming 
its  bed  or  support,  it  must  be  borne  in  mind  that  the  complete 
machine,  with  the  operator  in  the  aviator's  seat,  is  designed  to 
balance  on  a  point  about  1J  feet  back  of  the  front  edge  of  the  main 
planes.  As  the  operator  and  the  motor  represent  much  the  larger 
part  of  the  total  weight,  the  balance  may  easily  be  regulated  by 
moving  them  slightly  forward  or  backward,  as  may  be  required. 
It  will  be  necessary,  of  course,  to  place  the  engine  far  enough  back 
in  any  case  to  permit  the  propeller  blades  to  clear  the  planes.  The 
actual  installation  of  the  engine  itself  will  be  an  easy  matter  for  any- 
one who  has  had  any  experience  in  either  automobile  or  marine 
gasoline  motor  work.  It  is  designed  to  be  bolted  to  the  two  engine 
beams  in  the  same  manner  as  on  the  side  members  of  the  frame  of 
an  automobile,  or  the  engine  bed  in  a  boat.  Just  in  front  of  the 
engine  is  the  best  place  for  the  gasoline  tank,  which  should  be  cylin- 
drical wTith  tapering  ends,  to  cut  down  its  wind  resistance.  If  the 
designer  is  not  anxious  to  carry  out  points  as  fine  as  this,  a  light 
copper  cylindrical  tank  may  be  purchased  from  stock.  It  should 
hold  at  least  ten  gallons  of  gasoline.  In  front  of  the  tank  is  the 
radiator. 

Controls.  The  controls  may  be  located  to  conform  to  the 
builder's  own  ideas  of  accessibility  and  convenience.  Usually  the 
switch  is  placed  on  the  steering  column,  and  it  may  be  of  the  ordinary 
knife  variety,  or  one  of  the  special  switches  made  for  this  purpose, 
as  taste  may  dictate.  The  throttle  control  and  spark  advance  may 


615 


50  BUILDING  AND  FLYING  AN  AEROPLANE 

either  be  in  the  form  of  pedals,  working  against  springs,  or  of  small 
levers  working  on  a  notched  sector,  at  the  side  of  the  seat.  The 
complete  control,  levers,  and  sector  may  be  purchased  ready  to 
mount  whenever  desired,  as  they  are  made  in  this  form  for  both 
automobile  and  marine  work.  This  likewise  applies  to  the  wheel, 
which  it  would  not  pay  the  amateur  to  attempt  to  make. 

Another  pedal  should  work  a  brake  on  the  front  wheel,  the 
brake  shoe  consisting  of  a  strip  of  sheet  steel,  fastened  at  one  end 
to  the  fore  part  of  the  skid  and  pressed  against  the  wheel  by  a  bamboo 
rod  directly  connected  with  the  brake  pedal.  An  emergency  brake 
can  also  be  made  by  loosely  bolting  a  stout  bar  of  steel  on  the  skid 


Fig.  22.      Method  of  Starting  the  Engine  of  an  Aeroplane 

near  its  rear  end ;  one  end  of  this  bar  is  connected  to  a  lever  near  the 
seat,  so  that  when  this  lever  is  pulled  back  the  other  end  of  the  bar 
tends  to  dig  into  the  ground.  As  making  a  landing  is  one  of  the  most 
difficult  feats  for  the  amateur  aviator  to  master  and  sufficient  space 
for  a  long  run  after  alighting  is  not  always  available,  these  brakes 
will  be  found  a  very  important  feature  of  the  machine. 

The  engine  is  started  by  swinging  the  propeller,  and  this  is  an 
operation  requiring  far  more  caution  than  cranking  an  automobile 
motor.  Both  hands  should  be  placed  on  the  same  blade,  Fig.  22, 
and  the  latter  should  always  be  pulled  downward — never  upward. 


616 


BUILDING  AND  FLYING  AN  AEROPLANE          51 

With  the  switch  off,  first  turn  the  propeller  over  several  times  to 
fill  the  cylinders  with  gas,  leaving  it  just  ahead  of  dead  center  of  one 
of  the  cylinders,  and  with  one  blade  extending  upward  and  to  the 
left  at  a  45-degree  angle.  After  closing  the  switch,  take  the  left 
blade  with  both  hands  and  swing  it  downward  sharply,  getting  out 
of  the  way  of  the  following  blade  as  quickly  as  possible. 

Tests.  The  first  thing  to  be  done  after  the  propeller  is  finished 
and  mounted  on  the  engine  is  to  test  the  combination,  or  power 
plant  of  the  biplane,  for  speed  and  thrust,  or  pulling  power.  From 
these  two  quantities  it  will  be  easy  to  figure  the  power  that  the 
engine  is  delivering.  The  only  instruments  necessary  are  a  spring 
balance  reading  to  300  pounds  or  over;  a  revolution  counter,  such  as 
may  be  procured  at  any  machinist's  supply  house  for  a  dollar  or  two; 
and  a  watch.  One  end  of  the  spring  balance  is  fastened  to  the  front 
end  of  the  skid  and  the  other  to  a  heavy  stake  firmly  driven  in  the 
ground  a  few  feet  back.  The  wheels  of  the  biplane  should  be  set  on 
smooth  boards  so  that  they  will  not  offer  any  resistance  to  the  for- 
ward thrust.  When  the  engine  is  started  the  spring  balance  will 
give  a  direct  reading  of  the  pull  of  the  propeller. 

With  one  observer  noting  the  thrust,  another  should  check  the 
number  of  revolutions  the  engine  is  turning  per  minute.  To  do  this, 
a  small  hole  should  previously  have  been  countersunk  in  the  hub 
of  the  propeller  to  receive  the  conical  rubber  tip  of  the  revolution 
counter.  The  observer  stands  behind  the  propeller,  watch  in  one 
hand  and  revolution  counter  in  the  other.  At  the  beginning  of  the 
minute  period,  tjie  counter  is  pressed  firmly  against  the  hub,  and 
quickly  withdrawn  at  the  end  of  the  minute.  A  stop  watch  is 
naturally  an  advantage  for  the  purpose.  The  horse-power  is  figured  as 
follows,  assuming,  for  example,  a  thrust  of  250  pounds  at  1,200  r.  p.  m. 

250  X  1200  X  3.5  X  100     Q7  , 
- —  -  =37  n.  p. 

33.000  X  85 

As  before,  the  "~W  allows  for  the  slip  and  represents  the 
efficiency  of  the  propeller;  33,000  is  the  number  of  foot  pounds  per 
minute  or  the  equivalent  of  one  horse-power,  and  3.5  is  the  pitch  of 
the  propeller. 

Assembling  the  Biplane.  Assembling  the  machine  complete 
requires  more  space  than  is  available  in  the  average  workshop. 


617 


52          BUILDING  AND  FLYING  AN  AEROPLANE 

However,  it  is  possible  to  assemble  the  sections  of  the  planes  in  a 
comparatively  small  room,  carrying  the  work  far  enough  to  make 
sure  that  everything  will  go  together  properly  when  the  time  comes 
for  complete  assembly  at  the  testing  ground.  In  this  case,  it  is 
preferable  to  assemble  the  end  sections  first,  standing  them  away 
when  complete  to  make  room  for  the  central  section,  on  which  the 
running  gear  and  outriggers  are  to  be  built  up. 

The  builder  will  have  decided  by  this  time  whether  he  will 
make  his  machine  on  the  regular  plan,  with  one  main  rib  between 
each  section,  or  on  the  quick-detachable  plan,  which  has  two  main 
ribs  on  either  side  of  the  central  section,  as  previously  explained. 

It  is  desirable  to  be  able  to  assemble  two  sections  at  once  and 
this  should  be  possible  anywhere  as  it  requires  a  space  only  about 
6  by  13  feet.  Two  wood  2X4's,  about  12  feet  long,  should  be  nailed 
down  on  the  blocks  on  the  floor;  make  these  level  and  parallel  to 
each  other  at  a  distance  of  3  feet  6  inches  on  centers,  one  being  3 
inches  higher  than  the  other.  Strips  of  wood  should  be  nailed  on 
them,  so  as  to  hold  the  main  beams  of  the  frame  in  place  while  assem- 
bling. 

The  two  front  and  two  rear  beam  sections  are  laid  in  place  and 
joined  with  the  sheet-steel  sleeves,  the  flanges  of  the  sleeves  on  the 
inner  side  of  the  beams.  Then  through  the  sleeves  in  the  front 
beams,  which  are,  of  course,  those  on  the  higher  bed,  drill  the  holes 
for  the  strut  socket  bolts  (J  inch).  The  holes  for  the  outer  ones  go 
through  the  projecting  ends  of  the  beams;  those  for  the  inner  ones 
are  half  in  each  of  the  two  abutting  beams.  At  the  end  where  the 
central  section  joins  on,  a  short  length  of  wood  of  the  same  section 
may  be  inserted  in  the  sleeve  while  drilling,  the  hole.  An  assistant 
should  hold  the  beams  firmly  together  while  the  holes  are  being 
drilled. 

Now  lay  in  place  the  three  main  ribs  belonging  to  the  two  sec- 
tions under  construction  and  fasten  them  at  the  front  ends  by  putting 
in  place  the  strut  sockets  for  which  the  holes  have  been  drilled,  with 
a  turnbuckle  plate  under  each  socket,  Fig.  16.  The  strut  socket 
bolt  passes  through  the  main  rib  and  the  beam.  The  bed  on  which 
the  assembling  is  being  done,  should  be  cut  when  sufficiently  under 
the  joints  to  leave  room  for  the  projecting  bolt  ends.  Set  the  ribs 
square  with  the  front  beams,  then  arrange  the  rear  beams  so  that 


618 


BUILDING  AND  FLYING  AN  AEROPLANE  53 

their  joints  come  exactly  under  the  ribs;  clamp  the  ribs  down  and 
drill  a  true,  vertical  hole  through  the  rib  beam,  holding  the  two 
sections  of  the  beam  together  as  before.  Then  put  the  rear  strut 
sockets  in  place,  using  the  angle  washers  previously  described,  above 
and  below  the  rib. 

When  the  quick-detachable  plan  is  followed,  the  ribs  at  the 
inner  ends  of  the  double  section,  where  they  join  the  central  section, 
should  be  bolted  on  an  inch  from  the  ends  of  the  beam,  using  J-inch 
stove  bolts  instead  of  the  socket  bolts.  The  sleeves  should  be  slotted, 
so  that  they  can  slide  off  without  removing  these  bolts,  as  the  sleeves 
and  ribs  which  occupy  the  position  over  the  joints  of  the  beams, 
belong  to  the  central  section. 

The  sections  should  now  be  strung  up  with  the  diagonal  truss 
wires  which  will  make  them  rigid  enough  to  stand  handling.  The 
wires  are  attached  at  each  end  to  the  flange  bolts  of  the  sleeves. 
Either  one  or  two  turnbuckles  may  be  used  on  each  wire,  as  already 
explained;  if  but  one  turnbuckle  be  used,  the  other  end  of  the  wire 
may  be  conveniently  attached  to  a  strip  of  sheet  steel  bent  double 
and  drilled  for  the  bolt,  like  the  sheet-steel  slip  of  a  turnbuckle. 
The  attachment,  of  whatever  nature,  should  be  put  between  the 
end  and  the  flange  of  the  sleeve,  not  between  the  two  flanges. 

Three  or  four  ribs  can  be  used  on  each  section;  four  are  pref- 
erable on  sections  of  full  6-foot  length.  They  are,  of  course,  evenly 
spaced  on  centers.  At  the  front  ends,  they  are  attached  to  the  beam 
by  wood  screws  through  their  flattened  ferrules.  The  attachment  to 
the  rear  beam  is  made  with  a  slip  of  sheet  steel  measuring  J  by  3 
inches,  bent  over  the  rib  and  fastened  to  the  beam  at  each  side  with 
a  wood  screw.  A  long  wire  nail  is  driven  through  the  rib  itself  on 
the  beam. 

Four  double  sections  should  be  built  up  in  this  manner,  the 
right  and  left  upper  and  the  right  and  left  lower  sections.  LTppers 
and  lowers  are  alike  except  for  the  inversion  of  the  sockets  in  the 
upper  sections.  Rights  and  lefts  differ  in  that  the  outer  beams  are 
long  enough  to  fill  up  the  sleeves,  not  leaving  room  for  another  beam 
to  join  on. 

Inserting  the  struts  in  their  sockets  between  the  upper  and  lower 
sections  of  the  same  side  will  now  form  either  of  the  two  sides  of  the 
machine  complete.  Care  should  be  taken  to  get  the  rear  struts  the 


619 


54          BUILDING  AND  FLYING  AN  AEROPLANE 

proper  length  with  respect  to  the  front  ones  to  bring  the  upper  and 
lower  planes  parallel.  The  distance  from  the  top  of  the  lower  front 
beam  to  the  top  of  the  upper  front  beam  should  be  the  same  as  the 
distance  between  the  rows  of  bracing  holes  in  the  upper  and  lower 
main  ribs  just  above  and  below  the  rear  struts — about  4  feet  6  inches. 
It  should  hardly  be  necessary  to  mention  that  the  thick  edges  of  the 
struts  come  to  the  front — they  are  fish-shaped  and  a  fish  is  thicker 
at  the  head  than  at  the  tail. 

The  truss  wires  may  now  be  strung  on  in  each  square  of  the 
struts,  beams,  and  main  ribs,  using  turnbuckles  as  previously 
described.  The  wires  should  be  taut  enough  to  sing  a  low  note  when 
plucked  between  the  thumb  and  forefinger.  If  the  construction  is 
carried  out  properly,  the  framework  will  stand  square  and  true 
with  an  even  tension  on  all  the  wires.  It  is  permissible  for  the 
struts  to  slant  backward  a  little  as  seen  from  the  side,  but  all  should 
be  perfectly  in  line. 

For  adjusting  the  turnbuckles,  the  builder  should  make  for 
himself  a  handy  little  tool  usually  termed  a  nipple  wrench.  It  is 
simply  a  strip  of  steel  H  by  J  by  ^  inches,  with  a  notch  cut  in  the 
middle  of  the  long  sides  to  fit  the  flattened  ends  of  the  turnbuckle 
nipples.  This  is  much  handier  than  the  pliers  and  does  not  burr  up 
the  nipples. 

It  has  been  assumed  in  this  description  of  the  assembling  that 
the  builder  is  working  in  a  limited  space;  if,  on  the  contrary,  he  has 
room  enough  to  set  up  the  whole  frame  at  once,  the  work  will  be 
much  simpler.  In  this  case,  the  construction  bed  should  be  30  feet 
long.  First  build  up  the  upper  plane  complete,  standing  it  against 
the  wall  when  finished;  then  build  the  lower  plane,  put  the  struts 
in  their  sockets,  and  lay  on  the  upper  plane  complete. 

Returning  to  the  plan  of,  assembly  by  sections,  after  the  side 
sections  or  wings  of  the  machine  have  been  completed,  the  struts 
may  be  taken  out  and  the  sections  laid  aside.  The  middle  section, 
to  which  the  running  gear  and  outriggers  will  be  attached,  is  now  to 
be  built  up  in  the  same  way.  If  the  builder  is  following  the  plan 
in  which  there  is  one  main  rib  between  each  section,  it  will  be  neces- 
sary to  take  off  the  four  inner  main  ribs  from  the  sections  already 
completed,  to  be  used  at  the  ends  of  the  central  section.  The  plan 
drawing  of  the  complete  machine  shows  that  the  ribs  of  the  central 


620 


BUILDING  AND  FLYING  AN  AEROPLANE          55 

section  are  cut  off  just  back  of  the  rear  beam  to  make  room  for  the 
propeller.  This  is  necessary  in  order  to  set  the  motor  far  enough 
forward  to  balance  the  machine  properly.  The  small  ribs  in  this 
section  have  the  same  curve  but  are  cut  off  10  inches  shorter  at  their 
rear  ends,  and  the  stumps  are  smoothed  down  for  ferrules  like  those 
for  the  other  small  ribs.  In  the  plan  which  has  one  main  rib  between 
each  section,  the  main  rib  on  each  side  of  the  central  section  must 
be  left  full  length.  In  the  quick-detachable  plan  with  two  main 
ribs  on  each  side  of  the  central  section,  the  inner  ones,  which  really 
belong  to  this  section,  are  cut  off  short  like  the  small  ribs. 

In  the  drawing  of  the  complete  machine,  the  distance  between 
the  struts  which  carry  the  engine  bed  is  shown  as  2  feet.  This  is 
only  approximate, -as  the  distance  must  be  varied  to  suit  the  motor 
employed.  By  this  time,  the  builder  will  have  decided  what  engine 
he  is  going  to  use — or  can  get — and  should  drill  the  holes  for  the 
sockets  of  these  struts  with  due  respect  to  the  width  of  the  engine's 
supporting  feet  or  lugs,  remembering  that  the  engine  bed  beams  go 
on  the  inside  of  the  struts.  In  the  drawing  of  the  running  gear,  Fig. 
17,  the  distance  between  the  engine-bed  struts  has  been  designated 
A.  The  distances,  B,  on  each  side  are,  of  course,  approximately 
(6'—  2 A),  whatever  A  may  be. 


621 


BUILDING  AND  FLYING  AN 
AEROPLANE 

PART  II 
BUILDING  A  BLERIOT  MONOPLANE 

As  mentioned  in  connection  with  the  description  of  its  con- 
struction, the  Curtiss  biplane  was  selected  as  a  standard  of  this  type 
of  aeroplane  after  which  the  student  could  safely  pattern  for  a  number 
of  reasons.  It  is  not  only  remarkably  simple  in  construction,  easily 
built  by  anyone  with  moderate  facilities  and  at  a  slight  outlay,  but 
it  is  likewise  the  easiest  machine  to  learn  to  drive.  The  monoplane  is 
far  more  difficult  and  expensive  to  build. 

The  Bleriot  may  be  regarded  as  the  most  typical  example  in  this 
field,  in  view  of  its  great  success  and  the  very  large  numbers  which 
have  been  turned  out.  In  fact,  the  Bleriot  monoplane  is  the  product 
of  a  factory  which  would  compare  favorably  with  some  of  the  large 
automobile  plants.  Its  construction  requires  skillful  workmanship 
both  in  wood  and  metal,  and  a  great  many  special  castings,  forgings, 
and  stampings  are  necessary.  Although  some  concerns  in  this 
country  advertise  that  they  carry  these  fittings  as  stock  parts,  they 
are  not  always  correct  in  design  and,  in  any  case,  are  expensive. 
Wherever  it  is  possible  to  avoid  the  use  of  such  parts  by  any  expedient, 
both  forms  of  construction  are  described,  so  that  the  builder  may 
take  his  choice. 

Bleriot  monoplanes  are  made  in  a  number  of  different  models, 
the  principal  ones  being  the  30-horse-power  "runabout,"  Figs.  23 
and  24,  the  50-  and  70-horse-power  passenger-carrying  machines, 
and  the  50-,  70-,  and  100-horse-power  racing  machines.  Of  these  the 
first  has  been  chosen  as  best  adapted  to  the  purpose.  Its  construction 
is  typical  of  the  higher-power  monoplanes  of  the  same  make,  and  it 
is  more  suitable  for  the  beginner  to  fly  as  well  as  to  build.  It  is 
employed  exclusively  by  the  Bleriot  schools. 

Motor.  The  motor  regularly  employed  is  the  30-horse-power, 
three-cylinder  Anzani,  a  two-cylinder  type  of  which  is  shown  in 

Copyright,  1912,  by  American  School  of  Correspondence. 


623 


Fig.  23.     Details  of  Bleriot  Monoplane 

624 


625 


60 


BUILDING  AND  FLYING  AN  AEROPLANE 


"Aeronautical  Motors/'  Fig.  40.  From  the  amateur's  standpoint,  a 
disadvantage  of  the  Bleriot  is  the  very  short  space  allowed  for  the 
installation  of  the  motor.  For  this  reason,  the  power  plant  must  be 
fan  shaped,  like  the  Anzani;  star  form,  like  the  Gnome;  or  of  the 
two-cylinder  opposed  type.  It  must  likewise  be  air-cooled,  as  there 
is  no  space  available  for  a  radiator. 

Fuselage.  Like  most  monoplanes,  the  Bleriot  has  a  long  central 
body,  usually  termed  "fuselage,"  to  which  the  wings,  running  gear, 
and  controls  are  all  attached.  A  drawing  of  the  fuselage  with  all 
dimensions  is  reproduced  in  Fig.  25,  and  as  the  machine  is,  to  a  large 
extent,  built  up  around  this  essential,  its  construction  is  taken  up 
first.  It  consists  of  four  long  beams  united  by  35  crosspieces.  The 
beams  are  of  ash,  1^  inches  square  for  the  first  third  of  their  length 


Fig.  26.     Details  of  U-bolt  Which  Is  a  Feature  of  Bleriot  Construction 

and  tapering  to  |  inch  square  at  the  rear  ends.  Owing  to  the  diffi- 
culty of  securing  good  pieces  of  wood  the  full  length,  and  also  to 
facilitate  packing  for  shipment,  the  beams  are  made  in  halves,  the 
abutting  ends  being  joined  by  sleeves  of  If -inch,  20-gauge  steel 
tubing,  each  held  on  by  two  J-inch  bolts.  Although  the  length  of 
the  fuselage  is  21  feet  11 J  inches,  the  beams  must  be  made  of  two 
11 -foot  halves  to  allow  for  the  curve  at  the  rear  ends. 

The  struts  are  also  of  ash,  the  majority  of  them  being  f  by  1J 
inches,  and  oval  in  section  except  for  an  inch  and  a  half  at  each  end. 
But  the  first,  second,  and  third  struts  (counting  from  the  forward 
end)  on  each  side,  the  first  and  second  on  the  top,  and  the  first  strut 


626 


BUILDING  AND  FLYING  AN  AEROPLANE          61 

on  the  bottom  are  1^  inches  square,  of  the  same  stock  as  the  main 
beams.  Practically  all  of  the  struts  are  joined  to  the  main  beams 
by  u -bolts,  as  shown  by  the  detail  drawing,  Fig.  26,  this  being  one 
of  Louis  Bleriot's  inventions.  The  small  struts  are  held  by  J-inch 
bolts  and  the  larger  ones  by  j^-inch  bolts.  The  ends  of  the  struts 
must  be  slotted  for  these  bolts,  this  being  done  by  drilling  three  holes 
in  a  row  with  a  ^-  or  ^-inch  drill,  according  to  whether  the  slot  is 
for  the  smaller  or  larger  size  bolt.  The  wood  between  the  holes  is 
cut  out  with  a  sharp  knife  and  the  slot  finished  with  a  coarse,  flat  file. 

All  of  the  u -bolts  measure  2  inches  between  the  ends.  The 
vertical  struts  are  set  1  inch  forward  of  the  corresponding  horizontal 
struts,  so  that  the  four  holes  through  the  beam  at  each  joint  are 
spaced  1  inch  apart,  alternately  horizontal  and  vertical.  To  the 
projecting  angles  of  the  u -bolts  are  attached  the  diagonal  truss  wires, 
which  cross  all  the  rectangles  of  the  fuselage,  except  that  in  which  the 
driver  sits.  This  trussing  should  be  of  20-gauge  piano  wire  (music- 
wire  gauge)  or  ro-inch  cable,  except  in  the  rectangles  bounded  by 
the  large  struts,  where  it  should  be  25-gauge  piano  wire  or  ^-inch 
cable.  Each  wire,  of  course,  should  have  a  turnbuckle.  About  100 
of  these  will  be  required,  either  of  the  spoke  type  or  the  regular  type, 
with  two  screw  eyes — the  latter  preferred. 

Transverse  squares,  formed  by  the  two  horizontal  and  two 
vertical  struts  at  each  point,  are  also  trussed  with  diagonal  wires. 
Although  turnbuckles  are  sometimes  omitted  on  these  wires,  it  takes 
considerable  skill  to  get  accurate  adjustments  without  them.  The 
extreme  rear  strut  to  w\hich  the  rudder  is  attached,  is  not  fastened  in 
the  usual  way.  It  should  be  cut  with  tongues  at  top  and  bottom, 
fitting  into  notches  in  the  ends  of  the  beams,  and  the  whole  bound 
with  straps  of  20-gauge  sheet  steel,  bolted  through  the  beams  with 
f-inch  bolts. 

Continuing  forward,  the  struts  have  no  peculiarity  until  the 
upper  horizontal  one  is  reached,  just  behind  the  driver's  seat.  As  it 
is  impossible  to  truss  the  quadrangle  forward  of  this  strut,  owing  to 
the  position  of  the  driver's  body,  the  strut  is  braced  with  a  u -shaped 
half-round  strip  of  J  by  1  inch  of  ash  or  hickory  bolted  to  the  beams 
at  the  sides  and  to  the  strut  at  the  rear,  with  two  f-inch  bolts  at  each 
point.  The  front  side  of  the  strut  should  be  left  square  where  this 
brace  is  in  contact  with  it.  The  brace  should  be  steam  bent  with  the 


627 


62          BUILDING  AND  FLYING  AN  AEROPLANE 

curves  on  a  9-inch  radius,  and  the  half-round  side  on  the  inside  of 
the  curve. 

The  vertical  struts  just  forward  of  the  driver's  seat  carry  the 
inner  ends  of  the  rear  -wing  beams.  Each  beam  is  attached  with  a 
single  bolt,  giving  the  necessary  freedom  to  rock  up  and  down  in 
warping  the  wings.  The  upper  6  inches  of  each  of  these  struts  fits 
into  a  socket  designed  to  reinforce  it.  In  the  genuine  Bleriot,  this 
socket  is  an  aluminum  casting.  However,  a  socket  which  many  would 
regard  as  even  better  can  be  made  from  a  7-inch  length  of  20-gauge 
If -inch  square  tubing.  One  end  of  the  tube  is  sawed  one  inch  through 
the  corners;  two  opposite  sides  are  then  bent  down  at  right  angles  to 
form  flanges,  and  the  other  two  sides  sawed  off.  A  1-  by  3-inch  strip 
of  20-gauge  sheet  steel,  brazed  across  the  top  and  flanges  completes 
the  socket.  With  a  little  care,  a  very  creditable  socket  can  be  made 
in  this  way.  Finally,  with  the  strut  in  place,  a  f-inch  hole  is  drilled 
through  4  inches  from  the  top  of  the  socket  for  the  bolt  securing  the 
wing  beam. 

The  upper  horizontal  strut  at  this  point  should  be  arched  about 
six  inches  to  give  plenty  of  elbow  room  over  the  steering  wheel. 
The  bending  should  be  done  in  a  steam  press.  The  strut  should  be 
1&  inches  square,  cut  sufficiently  long  to  allow  for  the  curve,  and 
fitted  at  the  ends  with  sockets  as  described  above,  but  set  at  an  angle 
by  sawing  the  square  tube  down  further  on  one  side  than  on  the  other. 

On  the  two  lower  beams,  is  laid  a  floor  of  half-inch  boards, 
extending  one  foot  forward  and  one  foot  back  of  the  center  line  of  the 
horizontal  strut.  This  floor  may  be  of  spruce,  if  it  is  desired  to  save 
a  little  weight,  or  of  ordinary  tongue-and-grooved  floor  boards, 
fastened  to  the  beams  with  wood  screws  or  bolts.  The  horizontal 
strut  under  this  floor  may  be  omitted,  but  its  presence  adds  but  little 
weight  and  completes  the  trussing.  Across  the  top  of  the  fuselage 
above  the  first  upper  horizontal  strut,  lies  a  steel  tube  which  forms 
the  sockets  for  the  inner  end  of  the  front  wing  beams.  This  tube  is 
If  inches  diameter,  18  gauge,  and  26f  inches  long.  It  is  held  fast  by 
two  steel  straps,  16  gauge  and  1  inch  wide,  clamped  down  by  the  nuts 
of  the  vertical  strut  u -bolts.  The  center  of  the  tube  is,  therefore,  in 
line  with  the  center  of  the  vertical  struts,  not  the  horizontal  ones. 
The  u -bolts  which  make  this  attachment  are,  of  course,  the  f^-inch 
size,  and  one  inch  longer  on  each  end  than  usual.  To  make  a  neat 


628 


BUILDING  AND  FLYING  AN  AEROPLANE          63 

'job,  the  tube  may  be  seated  in  wood  blocks,  suitably  shaped,  but 
these  must  not  raise  it  more  than  a  small  fraction  of  an  inch  above 
the  top  of  the  fuselage,  as  this  would  increase  the  angle  of  incidence 
of  the  wings. 

The  first  vertical  struts  on  each  side  are  extras,  without  cor- 
responding horizontal  ones;  they  serve  only  to  support  the  engine. 
When  the  Gnome  motor  is  used,  its  central  shaft  is  carried  at  the 
centers  of  two  x-shaped,  pressed-steel  frames,  one  on  the  front  side, 
flush  with  the  end  of  the  fuselage  and  one  on  the  rear. 

Truss  Frame  Built  on  Fuselage.  In  connection  with  the  fuselage 
may  be  considered  the  overhead  truss  frame  and  the  warping  frame. 
The  former  consists  of  two  inverted  v's  of  20-gauge,  1-  by  f -inch  oval 
tubing,  joined  at  their  apexes  by  a  20-gauge,  J-inch  tube.  Each  V 
is  formed  of  a  single  piece  of  the  oval  tubing  about  5  feet  long.  The 
flattened  ends  of  the  horizontal  tube  are  fastened  by  a  bolt  in  the 
angles  of  the  v's.  The  center  of  the  horizontal  tube  should  be  2  feet 
above  the  top  of  the  fuselage.  The  flattened  lower  ends  of  the  rear  V 
should  be  riveted  and  brazed  to  strips  of  18-gauge  steel,  which  will 
fit  over  the  bolts  attaching  the  vertical  fuselage  struts  at  this  point. 
The  legs  of  the  front  V  should  be  slightly  shorter,  as  they  rest  on  top 
of  the  wing  socket  tube.  Each  should  be  held  down  by  a  single 
j^-inch  bolt,  passing  through  the  upper  wTall  of  the  tube  and  its 
retaining  strap;  these  bolts  also  serve  the  purpose  of  preventing  the 
tube  from  sliding  out  from  under  the  strap.  Each  side  of  the  frame 
is  now  braced  by  diagonal  wires  (Xo.  20  piano  wire,  or  i^-inch  cable) 
with  turnbuckles.  , 

At  the  upper  corners  of  this  frame  are  attached  the  wires  which 
truss  the  upper  sides  of  the  wings.  The  front  wires  are  simply 
fastened  under  the  head  and  nut  of  the  bolt  which  holds  the  frame 
together  at  this  corner.  The  attachment  of  the  rear  wires,  however, 
is  more  complex,  as  these  wires  must  run  over  pulleys  to  allow  for 
the  rocking  of  the  rear  wing  beams  when  the  wings  are  warped.  To 
provide  a  suitable  place  for  the  pulleys,  the  angle  of  the  rear  V  is 
enclosed  by  two  plates  of  20-gauge  sheet  steel,  one  on  the  front  and 
one  on  the  rear,  forming  a  triangular  box  1  inch  thick  fore  and  aft, 
and  about  2  inches  on  each  side,  only  the  bottom  side  being  open. 
These  plates  are  clamped  together  by  a  ^-inch  steel  bolt,  on  which 
are  mounted  the  pulleys.  There  should  be  sufficient  clearance  for 


629 


64          BUILDING  AND  FLYING  AN  AEROPLANE 

pulleys  1  inch  in  diameter.  The  wires  running  over  these  pulleys 
must  then  pass  through  holes  drilled  in  the  tube.  The  holes  should 
not  be  drilled  until  the  wings  are  on,  when  the  proper  angle  for  them 
can  be  seen.  The  cutting  and  bending  of  the  steel  plates  is  a  matter 
of  some  difficulty,  and  should  not  be  done  until  the  frame  is  otherwise 
assembled,  so  that  paper  patterns  can  be  cut  for  them.  They  should 
have  flanges  bent  around  the  tube,  secured  by  the  bolts  which  hold 
the  frame  together,  to  keep  them  from  slipping  off. 

The  oval  tubing  is  used  in  the  vertical  parts  of  this  frame, 
principally  to  reduce  the  wind  resistance,  being  placed  with  the 
narrow  side  to  the  front.  However,  if  this  tubing  be  difficult  to 
obtain,  or  if  price  is  a  consideration,  no  harm  will  be  done  by 
using  f-inch  round  tubing.  Beneath  the  floor  of  the  driver's  cockpit 
in  the  fuselage  is  the  w^arping  frame,  the  support  for  the  wTires  which 
truss  the  rear  wing  beams  and  also  control  the  warping. 

This  frame  is  built  up  of  four  f-inch,  20-gauge  steel  tubes,  each 
about  3  feet  long,  forming  an  inverted,  4-sided  pyramid.  The  front 
and  back  pairs  of  tubes  are  fastened  to  the  lower  fuselage  beams  with 
i^-inch  bolts  at  points  15  inches  front  and  back  of  the  horizontal 
strut.  At  their  lower  ends  the  tubes  are  joined  by  a  fixture  which 
carries  the  pulleys  for  the  warping  wires  and  the  lever  by  which  the 
pulleys  are  turned.  In  the  genuine  Bleriot,  this  fixture  is  a  special 
casting.  However,  a  very  neat  connection  can  be  made  with  a  piece 
of  i^-inch  steel  stock,  1J  by  6  inches,  bent  into  a  u-shape  with  the 
legs  1  inch  apart  inside.  The  flattened  ends  of  the  tubes  are  riveted 
and  brazed  to  the  outside  upper  corners  of  the  u,  and  a  bolt  to  carry 
the  pulleys  passes  through  the  lower  part,  high  enough  to  give  clear- 
ance for  2-inch  pulleys.  This  frame  needs  no  diagonal  wires. 

Running  Gear.  Passing  now  to  the  running  gear,  the  builder 
will  encounter  the  most  difficult  part  of  the  entire  machine,  and  it  is 
impossible  to  avoid  the  use  of  a  few  special  castings.  The  general 
plan  of  the  running  gear  is  shown  in  the  drawing  of  the  complete 
machine,  Figs.  23  and  24,  while  some  of  the  details  are  illustrated 
in  Fig.  27,  and  the  remainder  are  given  in  the  detail  sheet,  Fig.  28. 
It  will  be  seen  that  each  of  the  two  wheels  is  carried  in  a  double  fork, 
the  lower  fork  acting  simply  as  a  radius  rod,  while  the  upper  fork  is 
attached  to  a  slide  which  is  free  to  move  up  and  down  on  a  2-inch 
steel  tube.  This  slide  is  held  down  by  two  tension  springs,  consisting 


630 


BUILDING  AND  FLYING  AN  AEROPLANE          65 

of  either  rubber  tubes  or  steel  coil  springs,  which  absorb  the  shocks 
of  landing.  The  whole  construction  is  such  that  the  wheels  are  free 
to  pivot  sideways  around  the  tubes,  so  that  when  landing  in  a  quarter- 
ing wind  the  wheels  automatically  adjust  themselves  to  the  direction 
of  the  machine. 

Framework.  The  main  framework  of  the  running  gear  consists 
of  two  horizontal  beams,  two  vertical  struts,  and  two  vertical  tubes. 
The  beams  are  of  ash,  4f  inches  wide  in  the  middle  half,  tapering  to 
3J  inches  at  the  ends,  and  5  feet  2f  inches  long  overall.  The  upper 
beam  is  ff  inch  thick  and  the  lower  1  inch.  The  edges  of  the  beams 
are  rounded  off  except  at  the  points  where  they  are  drilled  for  bolt 
holes  for  the  attachment  of  other  parts.  The  two  upper  beams  of 
the  fuselage  rest  on  these  beams  and  are  secured  to  them  by  two 
3^-inch  bolts  each. 

The  vertical  struts  are  also  of  ash,  1^  inch  by  3  inches  and 
4  feet  2  inches  long  overall.  They  have  tenons  at  each  end  which  fit 
into  corresponding  square  holes  in  the  horizontal  beams.  The  two 
lower  fuselage  beams  are  fastened  to  these  struts  by  two  ^-inch 
through  bolts  and  steel  angle  plates  formed  from  ^-inch  sheet  steel. 
The  channel  section  member  across  the  front  sides  of  these  struts  is 
for  the  attachment  of  the  motor,  and  will  be  taken  up  later.  The 
general  arrangement  at  this  point  depends  largely  on  what  motor  is 
to  be  used,  and  the  struts  should  not  be  rounded  or  drilled  for  bolt 
holes  until  this  has  been  decided. 

From  the  lower  ends  of  these  struts  CC,  Fig.  27,  diagonal  struts 
DD  run  back  to  the  fuselage.  These  are  of  ash,  1^  by  2J  inches 
and  2  feet  6  inches  long.  The  rear  ends  of  the  struts  DD  are  fastened 
to  the  fuselage  beams  by  the  projecting  ends  of  the  U-bolts  of  the 
horizontal  fuselage  struts,  and  also  by  angle  plates  of  sheet  steel. 
At  the  lower  front  ends  the  struts  DD  are  fastened  to  the  struts  CC 
and  the  beam  E  by  steel  angle  plates,  and  the  beam  is  reinforced  by 
other  plates  on  its  under  side. 

Trussing.  In  the  genuine  Bleriot,  the  framework  is  trussed  by 
a  single  length  of  steel  tape,  1J  by  &  inch  and  about  11  feet  long, 
fastened  to  U-bolts  in  the  beam  A,  Fig.  27.  This  tape  runs  down 
one  side,  under  the  beam  E,  and  up  the  other  side,  passing  through 
the  beam  in  two  places,  where  suitable  slots  must  be  cut.  The  tape 
is  not  made  in  this  country,  but  must  be  imported  at  considerable 


631 


632 


y 


633 


68          BUILDING  AND  FLYING  AN  AEROPLANE 

expense.  Ordinary  sheet  steel  will  not  do.  If  the  tape  can  not  be 
obtained,  a  good  substitute  is  |-inch  cable,  which  then  would  be  made 
in  two  pieces  and  fastened  to  eye  bolts  at  each  end. 

The  two  steel  tubes  are  2  inches  in  diameter,  18-gauge,  and  about 
4  feet  10  inches  long.  At  their  lower  ends  they  are  flattened,  but 
cut  away  so  that  a  2-inch  ring  will  pass  over  them.  To  these  flat- 
tened ends  are  attached  springs  and  wires  which  run  from  each  tube 
across  to  the  hub  of  the  opposite  wheel.  The  purpose  of  these  is 
simply  to  keep  the  wheels  normally  in  position  behind  the  tubes. 
The  tubes,  it  will  be  noticed,  pass  through  the  lower  beam,  but  are 
sunk  only  J  inch  into  the  upper  beam.  They  are  held  in  place  by 
sheet-steel  sockets  on  the  lower  side  of  the  upper  beam  and  the  upper 
side  of  the  lower  beam.  The  other  sides  of  the  beams  are  provided 
with  flat  plates  of  sheet  steel.  The  genuine  Bleriot  has  these  sockets 
stamped  out  of  sheet  steel,  but  as  the  amateur  builder  will  not  have 
the  facilities  for  doing  this,  an  alternative  construction  is  given  here. 

In  this  method,  the  plates  are  cut  out  to  pattern,  the  material 
being  sheet  steel  3^  inch  thick,  and  a  J-inch  hole  drilled  through  the 
center,  a  2-inch  circle  then  being  drawn  around  this.  Then,  with  a 
cold  chisel  a  half  dozen  radial  cuts  are  made  between  the  hole  and 
the  circle.  Finally  this  part  of  the  plate  is  heated  with  a  blow-torch 
and  a  2-inch  piece  of  pipe  driven  through,  bending  up  the  triangular 
corners.  These  bent  up  corners  are  then  brazed  to  the  tubes,  and  a 
strip  of  light  sheet  steel  is  brazed  on  to  cover  up  the  sharp  edges. 
Of  course,  the  brazing  should  not  be  done  until  the  slides  GG,  Figs. 
27  and  28,  have  been  put  on.  When  these  are  once  in  place,  they 
have  to  stay  on  and  a  breakage  of  one  of  them,  means  the  replace- 
ment of  the  tube  as  well.  This  is  a  fault  of  the  Bleriot  design  that 
can  not  well  be  avoided.  It  should  be  noticed  that  the  socket  at  the 
upper  end,  as  well  as  its  corresponding  plate  on  the  other  side  of  the 
beam,  has  extensions  which  reinforce  the  beam  where  the  eye  bolts 
or  U -bolts  for  the  attachment  of  the  steel  tape  pass  through. 

Forks.  Next  in  order  are  the  forks  which  carry  the  wheels. 
The  short  forks  JJ,  Figs.  27  and  28,  which  act  simply  as  radius 
rods,  are  made  of  1-  by  f-inch  oval  tubing,  a  stock  size  which  was 
specified  for  the  overhead  truss  frame.  It  will  be  noticed  that  these 
are  in  two  parts,  fastened  together  with  a  bolt  at  the  front  end. 
The  regular  Bleriot  construction  calls  for  forged  steel  eyes  to  go  in 


634 


BUILDING  AND  FLYING  AN  AEROPLANE  69 

the  ends  of  tubes,  but  these  will  be  hard  to  obtain.  The  construction 
shown  in  the  drawings  is  much  simpler.  The  ends  of  the  tubes  are 
heated  and  flattened  until  the  walls  are  about  ^  inch  apart  inside. 
Then  a  strip  of  r^-inch  sheet  steel  is  cut  the  right  width  to  fit  in  the 
flattened  end  of  the  tube,  and  brazed  in  place.  The  bolt  holes  then 
pass  through  the  combined  thickness  of  the  tube  and  the  steel  strip, 
giving  a  better  bearing  surf  ace,  •  which  may  be  further  increased  by 
brazing  on  a  washer. 

The  long  forks  FF,  which  transmit  the  landing  shocks  to  the 
springs,  are  naturally  made  of  heavier  material.  The  proper  size 
tubing  for  them  is  1|  by  f  inches,  this  being  the  nearest  equivalent 
to  the  14  by  28  mm  French  tubing.  However,  this  is  not  a  stock 
size  in  this  country  and  can  only  be  procured  by  order,  or  it  can 
be  made  by  rolling  out  ft-inch  round  tubing.  If  the  oval  tubing 
can  not  be  secured,  the  round  can  be  employed  instead,  other  parts 
being  modified  to  correspond.  The  ends  are  reinforced  in  the  same 
way  as  described  for  the  small  forks. 

These  forks  are  strengthened  by  aluminum  clamps  //,  Figs.  27 
and  28,  which  keep  the  tubes  from  spreading  apart.  Here,  of 
course,  is  another  call  for  special  castings,  but  a  handy  workman 
may  be  able  to  improvise  a  satisfactory  substitute  from  sheet  steel. 
On  each  tube  there  are  four  fittings:  At  the  bottom,  the  collar  M 
to  which  the  fork  J  is  attached,  and  above,  the  slide  G  and  the  clamps 
K  and  L,  which  limit  its  movement.  The  collar  and  slide  should  be 
forged,  but  as  this  may  be  impossible,  the  drawings  have  been  pro- 
portioned for  castings^  The  work  is  simple  and  may  be  done  by  the 
amateur  with  little  experience.  The  projecting  studs  are  pieces  of 
f-inch,  14-gauge  steel  tubing  screwed  in  tight  and  pinned,  though  if 
these  parts  be  forged,  the  studs  should  be  integral. 

The  clamps  which  limit  the  movement  of  the  slides  are  to  be 
whittled  out  of  ash  or  some  other  hard  wood.  The  upper  clamp  is 
held  in  place  by  four  bolts,  which  are  screwed  up  tight;  but  when 
the  machine  makes  a  hard  landing  the  clamp  will  yield  a  little  and 
slip  up  the  tube,  thus  deadening  the  shock.  After  such  a  landing, 
the  clamps  should  be  inspected  and  again  moved  down  a  bit,  if 
necessary.  The  lower  clamps,  which,  of  course,  only  keep  the  wheels 
from  hanging  down  too  far,  have  bolts  passing  clear  through  the  tubes. 

To  the  projecting  lugs  on  the  slides  GG  are  attached  the  rubber 


635 


70  BUILDING  AND  FLYING  AN  AEROPLANE 

tube  springs,  the  lower  ends  connecting  with  eye  bolts  through  the 
beam  E.  These  rubber  tubes,  of  which  four  will  be  needed,  are  being 
made  by  several  companies  in  this  country  and  are  sold  by  supply 
houses.  They  should  be  about  14  inches  long,  unstretched,  and 
li  inches  in  diameter,  with  steel  tips  at  the  ends  for  attachment. 

Hub  Attachments.  The  hubs  of  the  two  wheels  are  connected 
with  the  link  P,  with  universal  joints  N  N  at  each  end.  In  case  the 
machine  lands  while  drifting  sidewise,  the  wheel  which  touches  the 
ground  first  will  swing  around  to  head  in  the  direction  in  which  the 
machine  is  actually  moving,  and  the  link  will  cause  the  other  wheel 
to  assume  a  parallel  position;  thus  the  machine  can  run  diagonally 
on  the  ground  without  any  tendency  to  upset. 

This  link  is  made  of  the  same  1-  by  f-inch  oval  tubing  used 
elsewhere  in  the  machine.  In  the  original  Bleriot,  the  joints  are 
carefully  made  up  with  steel  forgings.  But  joints  which  will  serve 
the  purpose  can  be  improvised  from  a  1-inch  cube  of  hard  wood  and 
three  steel  straps,  as  shown  in  the  sketch,  Fig.  27.  From  each  of 
these  joints  a  wire  runs  diagonally  to  the  bottom  of  the  tube  on  the 
other  side,  with  a  spring  which  holds  the  wheel  in  its  normal  position. 
This  spring  should  be  either  a  rubber  tube,  like  those  described  above, 
but  smaller,  or  a  steel  coil  spring.  In  the  latter  case,  it  should  be 
of  twenty  f-inch  coils  of  No.  25  piano  wire. 

Wheels.  The  wheels  are  regularly  28  by  2  inches,  corresponding 
to  the  700  by  50  mm  French  size,  with  30  spokes  of  12-gauge  wire. 
The  hub  should  be  5J  inches  wide,  with  a  f-inch  bolt.  Of  course, 
these  sizes  need  not  be  followed  exactly,  but  any  variations  will 
involve  corresponding  changes  in  the  dimensions  of  the  forks.  The 
long  fork  goes  on  the  hub  inside  of  the  short  fork,  so  that  the  inside 
measurement  of  the  end  of  the  big  fork  should  correspond  to  the 
width  of  the  hub,  and  the  inside  measurement  of  the  small  fork 
should  equal  the  outside  measurement  of  the  large  fork. 

Rear  Skid.  Several  methods  are  employed  for  supporting  the  rear 
end  of  the  fuselage  when  the  machine  is  on  the  ground.  The  first  Ble- 
riot carried  a  small  wheel  in  a  fork  provided  with  rubber  springs,  the 
same  as  the  front  wheels.  The  later  models,  however,  have  a  double 
U-shaped  skid,  as  shown  in  Figs.  23  and  24.  This  skid  is  made  of 
two  8-foot  strips  of  ash  or  hickory  £  by  f  inches,  steamed  and  bent 
to  the  u -shape  as  shown  in  the  drawing  of  the  complete  machine. 


636 


637 


72       IBUILDING  AND  FLYING  AN  AEROPLANE 

Wings.  Having  completed  the  fuselage  and  running  gear,  the 
wings  are  next  in  order.  These  are  constructed  in  a  manner  which 
may  seem  unnecessarily  complicated,  but  which  gives  great  strength 
for  comparatively  little  weight.  Each  wing  contains  two  stout  ash 
beams  which  carry  their  share  of  the  weight  of  the  machine,  and 
12  ribs  which  give  the  proper  curvature  to  the  surfaces  and  at  the 
same  time  reinforce  the  beams.  These  ribs  in  turn  are  tied  together 
and  reinforced  by  light  strips  running  parallel  to  the  main  beams. 

In  the  drawing  of  the  complete  wing,  Fig.  29,  the  beams  are 
designated  by  the  letters  B  and  E.  A  is  a  sheet  aluminum  member 
intended  to  hold  the  cloth  covering  in  shape  on  the  front  edge.  C,  D, 
and  F  are  pairs  of  strips  (one  strip  on  top,  the  other  underneath) 
which  tie  the  ribs  together.  G  is  a  strip  along  the  rear  edge,  and  // 


Fig.  30.     Complete  Rib  of  Bleriot  Wing  and  Pattern  from  Which  Web  Is  Cut 

is  a  bent  strip  which  gives  the  rounded  shape  to  the  end  of  the  wing. 
The  ribs  are  designated  by  the  numbers  1  to  12  inclusive. 

Ribs.  The  first  and  most  difficult  operation  is  to  make  the  ribs. 
These  are  built  up  of  a  spruce  board  ^  inch  thick,  cut  to  shape  on 
a  jig  saw,  with  3^-  by  f-inch  spruce  strip  stacked  and  glued  to  the 
upper  and  lower  edges.  Each  rib  thus  has  an  I -beam  section,  such 
as  is  used  in  structural  steel  work  and  automobile  front  axles.  Each 
of  the  boards,  or  webs  as  they  are  usually  called,  is  divided  into  three 
parts  by  the  main  beams  which  pass  through  it.  Builders  sometimes 
make  the  mistake  of  cutting  out  each  web  in  three  pieces,  but  this 
makes  it  very  difficult  to  put  the  rib  together  accurately.  Each  web 
should  be  cut  out  of  a  single  piece,  as  shown  in  the  detail  drawing, 
Fig.  30,  and  the  holes  for  the  beams  should  be  cut  in  after  the  top 
and  bottom  strips  have  been  glued  on. 


638 


BUILDING  AND  FLYING  AN  AEROPLANE          73 

The  detail  drawing,  Fig.  30,  gives  the  dimensions  of  a  typical 
rib.  This  should  be  drawn  out  full  size  on  a  strip  of  tough  paper, 
and  then  a  margin  of  ^  inch  should  be  taken  off  all  round  except  at 
the  front  end  where  the  sheet  aluminum  member  A  goes  on.  This 
allows  for  the  thickness  of  the  top  and  bottom  strips.  In  preparing 
the  pattern  for  the  jig  saw,  the  notches  for  strips  C,  D,  and  F  should 
be  disregarded;  neither  should  it  be  expected  that  the  jig-saw 
operator  will  cut  out  the  oval  holes  along  the  center  of  the  web, 
which  are  simply  to  lighten  it.  The  notches  for  the  front  ends  of  the 
top  and  bottom  strips  should  also  be  smoothed  over  in  the  pattern. 

When  the  pattern  is  ready,  a  saw  or  planing  mill  provided  with 
a  saw  suitable  for  the  work,  should  cut  out  the  40  ribs  (allowing  a 
sufficient  number  for  defective  pieces  and  breakage)  for  about  $2. 
The  builder  then  cuts  the  notches  and  makes  the  oval  openings  with 
an  auger  and  keyhole  saw.  Of  course,  these  holes  need  not  be 
absolutely  accurate,  but  at  least  f  inch  of  wood  should  be  left  all 
around  them. 

Nine  of  the  twelve  ribs  in  each  wing  are  exactly  alike.  No.  1, 
which  forms  the  inner  end  of  the  wing,  does  not  have  any  holes  cut 
in  the  web,  and  instead  of  the  slot  for  the  main  beam  B,  has  a  1  J-inch 
round  hole,  as  the  stub  end  of  the  beam  is  rounded  to  fit  the  socket 
tube.  (See  Fig.  23.)  Rib  No.  11  is  5  feet  10J  inches  long,  and  No.  12 
is  3  feet  long.  These  can  be  whittled  out  by  hand,  and  the  shape  for 
them  will  be  obvious  as  soon  as  the  main  part  of  the  wing  is  put 
together. 

The  next  step  ( is  to  glue  on  the  top  and  bottom  strips.  The 
front  ends  should  be  put  on  first  and  held,  during  the  drying,  in  a 
scre\v  clamp,  the  ends  setting  close  up  into  the  notches  provided  for 
them.  Thin  J-inch  brads  should  be  driven  in  along  the  top  and 
bottom  at  1-  to  2-inch  intervals.  The  rear  ends  of  the  strips  should 
be  cut  off  to  the  proper  length  and  whittled  off  a  little  on  the  inside, 
so  that  there  will  be  room  between  them  for  the  strip  G,  J  inch  thick. 
Finally,  cut  the  slots  for  the  main  beams,  using  a  bit  and  brace  and 
the  keyhole  saw,  and  the  ribs  will  be  ready  to  assemble. 

Beams  and  Strips.  The  main  beams  are  of  ash,  the  front  beam 
in  each  wing  being  3J  by  f  inches  and  the  rear  beam  2J  by  f  inches. 
They  are  not  exactly  rectangular  but  must  be  planed  down  slightly 
on  the  top  and  bottom  edges,  so  that  they  will  fit  into  the  irregularly- 


639 


74  BUILDING  AND  FLYING  AN  AEROPLANE 

shaped  slots  left  for  them  in  the  ribs.  The  front  beams,  as  mentioned 
above,  have  round  stubs  which  fit  into  the  socket  tube  on  the  fusel- 
age. These  stubs  may  be  made  by  bolting  short  pieces  of  ash  board 
on  each  side  of  the  end  of  the  beam  and  rounding  down  the  whole. 

To  give  the  wings  their  slight  inclination,  or  dihedral  angle, 
which  will  be  apparent  in  the  front  view  of  the  machine,  the  stubs 
must  lie  at  an  angle  of  2J  degrees  with  the  beam  itself.  This  angle 
should  be  laid  out  very  carefully,  as  a  slight  inaccuracy  at  this  point 
will  result  in  a  much  larger  error  at  the  tips.  The  rear  beams  project 
about  2  inches  from  the  inner  ribs.  The  ends  should  be  reinforced 
with  bands  of  sheet  steel  to  prevent  splitting,  and  each  drilled  with 
a  f -inch  hole  for  the  bolt  which  attaches  to  the  fuselage  strut.  A 
strip  of  heavy  sheet  steel  should  be  bent  to  make  an  angle  washer 
to  fill  up  the  triangular  space  between  the  beam  and  the  strut;  the 
bolt  hole  should  be  drilled  perpendicularly  to  the  beam,  and  not  to 
the  strut.  The  outer  ends  of  the  beams,  beyond  rib  No.  10,  taper 
down  to  1  inch  deep  at  the  ends. 

The  aluminum  member  A,  Fig.  29,  which  holds  the  front  edge 
of  the  wing  in  shape,  is  made  of  a  4-inch  strip  of  fairly  heavy  sheet 
aluminum,  rolled  into  shape  round  a  piece  of  half-round  wood,  2J 
inches  in  diameter.  As  sheet  aluminum  usually  comes  in  6-foot 
lengths,  each  of  these  members  will  have  to  be  made  in  two  sections, 
joined  either  by  soldering  (if  the  builder  has  mastered  this  difficult 
process)  or  by  a  number  of  small  copper  rivets. 

No  especial  difficulties  are  presented  by  the  strips,  C,  D,  and  F, 
which  are  of  spruce  &  by  f  inch,  or  by  the  rear  edge  strip  G,  of  spruce 
\  by  IJ  inches.  Each  piece  //  should  be  1  by  J  inch  half-round 
spruce,  bent  into  shape,  fitted  into  the  aluminum  piece  at  the  front, 
and  at  the  rear  flattened  down  to  J  inch  and  reinforced  by  a  small 
strip  glued  to  the  back,  finally  running  into  the  strip  G.  The  exact 
curve  of  this  piece  does  not  matter,  provided  it  is  the  same  on  both 
wings. 

Assembling  the  Wings.  Assembling  the  wings  is  an  operation 
which  demands  considerable  care.  The  main  beams  should  first  be 
laid  across  two  horses,  set  level  so  that  there  will  be  no  strain  on  the 
framework  as  it  is  put  together.  Then  the  12  ribs  should  be  slipped 
over  the  beams  and  evenly  spaced  13  inches  apart  to  centers,  care 
being  taken  to  see  that  each  rib  stands  square  with  the  beams,  Fig.  31. 


640 


BUILDING  AND  FLYING  AN  AEROPLANE 


75 


The  ribs  are  not  glued  to  the  beams,  as  this  would  make  repairs 
difficult,  but  are  fastened  with  small  nails. 

Strips  C,  D,  and  F,  Fig.  29,  are  next  put  in  place,  simply  being 
strung  through  the  rows  of  holes  provided  for  them  in  the  ribs,  and 
fastened  with  brads.  Then  spacers  of  ^-inch  spruce,  2  or  3  inches 
long,  are  placed  between  each  pair  of  strips  halfway  between  each 
rib,  and  fastened  with  glue  and  brads.  This  can  be  seen  in  the 
broken-off  view  of  the  wing  in  the  front  view  drawing,  Fig.  23. 
The  rear  edge  strip  fits  between  the  ends  of  the  top  and  bottom 


Fig.  31.     Assembling  the  Main  Planes  of  a  Bleriot  Monoplane 

strips  of  the  ribs,  as  mentioned  above,  fastened  with  brads  or  with 
strips  of  sheet-aluminum  tacked  on. 

Each  wing  is  trussed  by  eight  wires,  half  above  and  half  below ; 
half  attached  to  the  front  and  half  to  the  rear  beam.  In  the  genuine 
Bleriot  steel  tape  is  used  for  the  lower  trussing  of  the  main  beams, 
similar  to  the  tape  employed  in  the  running  gear,  but  American 
builders  prefer  to  use  f-inch  cable.  The  lower  rear  trussing  should 
be  3%-  or  t^-inch  cable,  and  the  upper  trussing  ^-inch. 

The  beams  are  provided  with  sheet-steel  fixtures  for  the  attach- 
ment of  the  cables,  as  shown  in  the  broken-off  wing  view,  Fig.  23. 
These  are  cut  from  fairly-heavy  metal,  and  go  in  pairs,  one  on  each 


641 


76          BUILDING  AND  FLYING  AN  AEROPLANE 


side  of  the  and  beam,  fasten  with  three  j^-inch  bolts.  They  have 
lugs  top  and  bottom.  They  are  placed  between  the  fifth  and  sixth 
and  ninth  and  tenth  ribs  on  each  side. 

To  resist  the  backward  pressure  of  the  air,  the  wings  are  trussed 
with  struts  of  1-inch  spruce  and  ^-inch  cable,  as  shown  in  Fig.  23. 
The  struts  are  placed  between  the  cable  attachments,  being  provided 
with  ferrules  of  flattened  steel  tubing  arranged  to  allow  the  rear  beam 
freedom  to  swing  up  and  down.  The  diagonal  cables  are  provided 
with  turnbuckles  and  run  through  the  open  spaces  in  the  ribs. 

Control  System.  The  steering  gear  and  tail  construction  of  the 
Bleriot  are  as  distinctive  as  the  swiveling  wheels  and  the  u  -bolts,  and 
the  word  "cloche"  applied  to  the  bell-like  attachment  for  the  control 
wires,  has  been  adopted  into  the  international  vocabulary  of  aero- 
planing.  The  driver  has  between  his  knees  a  small  steering  wheel 
mounted  on  a  short  vertical  post.  This  wheel  does  not  turn,  but 
instead  the  post  has  a  universal  joint  at  the  bottom  which  allows  it 
to  be  swung  backward  and  forward  or  to  either  side.  The  post  is 
really  a  lever,  and  the  wheel  a  handle.  Encircling  the  lower  part  of 
the  post  is  a  hemispherical  bell  —  the  cloche  —  with  its  bottom  edge  on 
the  same  level  as  the  universal  joint. 

Four  wires  are  attached  to  the  edge  of  the  cloche.  Those 
at  the  front  and  back  are  connected  with  the  elevator,  and  those  at 
the  sides  with  the  wing-warping  lever.  The  connections  are  so 
arranged  that  pulling  the  wheel  back  starts  the  machine  upward, 
while  pushing  it  forward  causes  it  to  descend,  and  pulling  to  either 
side  lowers  that  side  and  raises  the  other.  The  machine  can  be  kept 
on  a  level  keel  by  the  use  of  the  wheel  and  cloche  alone;  the  aviator 
uses  them  just  as  if  they  were  rigidly  attached  to  the  machine,  and 
by  them  he  could  move  the  machine  bodily  into  the  desired  position. 

In  practice,  however,  it  has  been  found  that  lateral  stability  can 
be  maintained  more  easily  by  the  use  of  the  vertical  rudder  than  by 
warping.  This  is  because  the  machine  naturally  tips  inward  on  a 
turn,  and,  consequently,  a  tip  can  be  corrected  by  a  partial  turn  in 
the  other  direction.  If,  for  example,  the  machine  tips  to  the  right, 
the  aviator  steers  slightly  to  the  left,  and  the  machine  comes  back 
to  a  level  keel  without  any  noticeable  change  in  direction.  Under 
ordinary  circumstances  this  plan  is  used  altogether,  and  the  warping 
is  used  only  on  turns  and  in  bad  weather. 


642 


BUILDING  AND  FLYING  AN  AEROPLANE 


77 


It  will  be  noticed  that  the  Bleriot  control  system  is  almost 
identical  with  that  of  the  Henri  Farman  biplane,  the  only  difference 
being  that  in  the  Farman  the  cloche  and  wheel  are  replaced  by  a 
long  lever.  The  movements,  however,  remain  the  same,  and  as  there 
are  probably  more  Bleriot  and  Farman  machines  in  use  than  all  other 
makes  together,  this  control  may  be  regarded  almost  as  a  standard. 
It  is  not  as  universal  as  the  steering  wheel,  gear  shift,  and  brake 
levers  of  the  automobile,  but  still  it  is  a  step  in  the  right  direction. 


J 

( 

T 

,  — 

SfDE  V/EW 

\ 

-T; 
END  V/EW 



Fig.  32.     Control  Device  of  Steel  Tubing  instead  of  Bleriot  "Cloche" 

In  the  genuine  Bleriot,  the  cloche  is  built  up  of  two  bells,  one 
inside  the  other,  both  of  sheet  aluminum  about  ^  inch  thick.  The 
outer  bell  is  11  inches  in  diameter  and  3J  inches  deep,  and  the  inner 
one  10  inches  in  diameter  and  2  inches  deep.  A  ring  of  hard  wood 
is  clamped  between  their  edges  and  the  steering  column,  an  aluminum 
casting  passing  through  their  centers.  This  construction  is  so  com- 
plicated and  requires  so  many  special  castings  and  parts  that  it  is 
almost  impossible  for  the  amateur. 


643 


78          BUILDING  AND  FLYING  AN  AEROPLANE 

Steering  Gear.  While  not  so  neat,  the  optional  construction 
shown  in  the  accompanying  drawing,  Fig.  32,  is  equally  effective. 
In  this  plan,  the  cloche  is  replaced  by  four  V-shaped  pieces  of  J-inch, 
20-gauge  steel  tubing,  attached  to  a  steering  post  of  1-inch,  20-gauge 
tubing.  At  the  lower  end,  the  post  has  a  fork,  made  of  pieces  of 
smaller  tubing  bent  and  brazed  into  place,  and  this  fork  forms  part 
of  the  universal  joint  on  which  the  post  is  mounted.  The  cross  of 
the  universal  joint,  which  is  somewhat  similar  to  those  employed  on 
automobiles,  can  best  be  made  of  two  pieces  of  heavy  tubing,  |  inch 
by  12  gauge,  each  cut  half  away  at  the  middle.  The  two  pieces  are 
then  fastened  together  by  a  small  bolt  and  brazed  for  greater  security. 
The  ends  which  are  to  go  into  the  fork  of  the  steering  post  must  then 
be  tapped  for  f-inch  machine  screws.  The  two  other  ends  of  the 
cross  are  carried  on  V's  of  J-inch,  20-gauge  tubing,  spread  far  enough 
apart  at  the  bottom  to  make  a  firm  base,  and  bolted  to  the  floor  of 
the  cockpit. 

The  steering  wheel  itself  is  comparatively  unimportant.  On 
the  genuine  Bleriot  it  is  a  solid  piece  of  wood  8  inches  in  diameter, 
with  two  holes  cut  in  it  for  hand  grips.  On  the  post  just  under  the 
wheel  are  usually  placed  the  spark  and  throttle  levers.  It  is  rather 
difficult,  however,  to  arrange  the  connections  for  these  levers  in  such 
a  wray  that  they  will  not  be  affected  by  the  movements  of  the  post, 
and  for  this  reason  many  amateur  builders  place  the  levers  at  one 
side  on  one  of  the  fuselage  beams. 

From  the  sides  of  the  cloche,  or  from  the  tubing  triangles  which 
may  be  substituted  for  it,  two  heavy  wires  run  straight  down  to  the 
ends  of  the  warping  lever.  This  lever,  together  with  two  pulleys, 
is  mounted  at  the  lower  point  of  the  warping  frame  already  described. 
The  lever  is  12  inches  long,  11  inches  between  the  holes  at  its  ends, 
and  2  inches  wide  in  the  middle;  it  should  be  cut  from  a  piece  of 
sheet  steel  about  ^  inch  thick.  The  pulleys  should  be  2|  inches  in 
diameter,  one  of  them  bolted  to  the  lever,  the  other  one  running 
free.  The  wires  from  the  outer  ends  of  the  rear  wing  beams  are 
joined  by  a  piece  of  flexible  control  cable,  which  is  given  a  single 
turn  over  the  free  pulley.  The  inner  wires,  however,  each  have  a 
piece  of  flexible  cable  attached  to  their  ends,  and  these  pieces  of 
cable,  after  being  given  a  turn  round  the  other  pulley,  are  made  fast 
to  the  opposite  ends  of  the  warping  lever.  These  cables  should  be 


644 


BUILDING  AND  FLYING  AN  AEROPLANE          79 

run  over  the  pulleys,  not  under,  so  that  when  the  cloche  is  pulled 
to  the  right,  the  left  wing  will  be  warped  downward. 

It  is  a  common  mistake  to  assume  that  both  pulleys  are  fastened 
to  the  warping  lever;  but  when  this  is  done  the  outer  wire  slackens 
off  and  does  not  move  in  accord  with  the  inner  wire,  on  account  of 
the  different  angles  at  which  they  work. 

Foot  Levers.  The  foot  lever  for  steering  is  cut  from  a  piece  of 
wood  22  inches  long,  hollowed  out  at  the  ends  to  form  convenient 
rests  for  the  feet.  The  wires  connecting  the  lever  to  the  rudder  may 
either  be  attached  to  this  lever  direct,  or,  if  a  neater  construction  is 
desired,  they  may  be  attached  to  another  lever  under  the  floor  of  the 
cockpit.  In  the  latter  case,  a  short  piece  of  1-inch  steel  tubing  serves 
as  a  vertical  shaft  to  connect  the  two  levers,  which  are  fastened  to 
the  shaft  by  means  of  aluminum  sockets  such  as  may  be  obtained 
from  any  supply  house.  The  lower  lever  is  12  inches  long  and  2 
inches  wide,  cut  from  ^-inch  steel  similar  to  the  warping  lever. 

Amateur  builders  often  cross  the  rudder  wires  so  that  pressing 
the  lever  to  the  right  will  cause  the  machine  to  steer  to  the  left. 
This  ma.y  seem  more  natural  at  first  glance,  but  it  is  not  the  Bleriot 
way.  Iri  the  latter,  the  wires  are  not  crossed,  the  idea  being  to 
facilitate  the  use  of  the  vertical  rudder  for  maintaining  lateral  equi- 
librium. With  this  arrangement,  pressing  the  lever  with  the  foot  on 
the  high  side  of  the  machine  tends  to  bring  it  back  to  an  even  keel. 

Tail  and  Elevator.  The  tail  and  elevator  planes  are  built  up 
with  ribs  and  tie  strips  in  much  the  same  manner  as  the  wings. 
However,  it  will  hardly  pay  to  have  these  ribs  cut  out  on  a  jig  saw 
unless  the  builder  can  have  this  work  done  very  cheaply.  It  serves 
the  purpose  just  as  well  to  clamp  together  a  number  of  strips  of 
iVinch  spruce  and  plane  them  down  by  hand.  The  ribs  when 
finished  should  be  24J  inches  long.  The  greatest  depth  of  the  curve 
is  1J  inches,  at  a  point  one-third  of  the  way  back  from  the  front 
edge,  and  the  greatest  depth  of  the  ribs  themselves  2J  inches,  at  the 
same  point.  Sixteen  ribs  are  required. 

A  steel  tube  1  inch  by  20  gauge,  C,  Fig.  33,  runs  through  both 
tail  and  elevators,  and  is  the  means  of  moving  the  latter.     Each  rib 
at  the  point  where  the  tube  passes  through,  is  provided  with  an 
aluminum  socket.     Those  on  the  tail  ribs  act  merely  as  bearings 
for  the  tube,  but  those  on  the  elevator  ribs  are  bolted  fast,  so  that 


645 


ft- 

^ 


1 

% 


646 


BUILDING  AND  FLYING  AN  AEROPLANE          81 

the  elevators  must  turn  with  the  tube.  At  its  center  the  tube  carries 
a  lever  G,  of  r^-inch  steel  12  by  2  inches,  fastened  on  by  two  aluminum 
sockets,  one  on  each  side.  From  the  top  of  the  lever  a  wire  runs  to 
the  front  side  of  the  cloche,  and  from  the  bottom  a  second  wire  runs 
to  the  rear  side  of  the  cloche. 

The  tube  is  carried  in  two  bearings  HH,  attached  to  the  lower 
beams  of  the  fuselage.  These  are  simply  blocks  of  hard  wood, 
fastened  by  steel  strips  and  bolts.  The  angle  of  incidence  of  the 
tail  is  adjustable,  the  tail  itself  being  held  in  place  by  two  vertical 
strips  of  steel  rising  from  the  rear  edge  and  bolted  to  the  fuselage, 
as  shown  in  the  drawing,  Fig.  33.  To  prevent  the  tail  from  folding 
up  under  the  air  pressure  to  which  it  is  subjected,  it  is  reinforced 
by  two  f-inch,  20-gauge  steel  tubes  running  down  from  the  upper 
sides  of  the  fuselage,  as  shown  in  the  drawing  of  the  complete  machine, 
Fig.  23. 

The  tail  and  elevators  have  two  pairs  of  tie  strips,  B  and  7), 
Fig.  33,  made  of  ^-  by  f-inch  spruce.  The  front  edge  A  is  half 
round,  1-  by  J-inch  spruce,  and  the  rear  edge  E  is  a  spruce  strip 
J-  by  IJ-inches.  The  end  pieces  are  curved. 

Rudder.  The  rudder  is  built  up  on  a  piece  of  1-inch  round 
spruce  M ,  corresponding  in  a  way  to  the  steel  tube  used  for  the 
elevators.  On  this  are  mounted  two  long  ribs  KK,  and  a  short  rib 
J,  made  of  spruce  f  inch  thick  and  If  inches  wide  at  the  point  where 
M  passes  through  them.  They  are  fastened  to  M  with  f-inch  through 
bolts.  The  rudder  lever  N,  of  ^-inch  steel,  12  by  2  inches,  is  laid 
flat  on  J  and  bolted  in  place;  it  is  then  trussed  by  wires  running 
from  each  end  to  the  rear  ends  of  KK.  From  the  lever  other  wires 
also  run  forward  to  the  foot  lever  which  controls  the  rudder. 

The  wires  to  the  elevator  and  rudder  should  be  of  the  flexible 
cable  specially  made  for  this  purpose,  and  should  be  supported  by 
fairleaders  attached  to  the  fuselage  struts.  Fairleaders  of  different 
designs  may  be  procured  from  supply  houses,  or  may  be  improvised. 
Ordinary  screw  eyes  are  often  used,  or  pieces  of  copper  tubing,  bound 
to  the  struts  with  friction  tape. 

Covering  the  Planes.  Covering  the  main  planes,  tail,  elevators, 
and  rudder  may  wTell  be  left  until  the  machine  is  otherwise  ready 
for  its  trial  trip,  as  the  cloth  will  not  then  be  soiled  by  the  dust  and 
grime  of  the  shop.  The  cloth  may  be  any  of  the  standard  brands 


647 


82 


BUILDING  AND  FLYING  AN  AEROPLANE 


which  are  on  the  market,  preferably  in  a  rather  light  weight  made 
specially  for  double-surfaced  machines  of  this  type;  or  light-weight 
sail  cloth  may  be  used,  costing  only  25  or  30  cents  a  yard.  About 
80  yards  will  be  required,  assuming  a  width  of  36  inches. 

Except  on  the  rudder,  the  cloth  is  applied  on  the  bias,  the  idea 
being  that  with  this  arrangement  the  threads  act  like  diagonal  truss 
wires,  thus  strengthening  and  bracing  the  framework.  When  the 
cloth  is  to  be  put  on  in  this  way  it  must  first  be  sewed  together  in 
sheets  large  enough  to  cover  the  entire  plane.  Each  wing  will  require 


Fig.  34.     Method  of  Mounting  Fabric  on  Main  Supporting  Frame 

a  sheet  about  14  feet  square,  and  two  sheets  each  6  feet  square  will 
be  required  for  the  elevators  and  tail.  The  strips  of  cloth  run 
diagonally  across  the  sheets,  the  longest  strips  in  the  wing  sheets 
being  20  feet  long. 

Application  of  the  cloth  to  the  wings,  Fig.  34,  is  best  begun 
by  fastening  one  edge  of  a  sheet  to  the  rear  edge  of  the  wing,  stretch- 
ing the  cloth  as  tight  as  can  be  done  conveniently  with  one  hand. 
The  cloth  is  then  spread  forward  over  the  upper  surface  of  the  wing 
and  is  made  fast  along  the  inner  end  rib.  Small  copper  tacks  are 
used,  spaced  2  inches  apart  on  the  upper  side  and  1  inch  on  the 


648 


BUILDING  AND  FLYING  AN  AEROPLANE          83 

lower  side.  After  the  cloth  has  been  tacked  to  the  upper  sides  of 
all  the  ribs,  the  wing  is  turned  over  and  the  cloth  stretched  over 
the  lower  side.  Finally  the  raw  edges  are  trimmed  off  and  covered 
with  light  tape  glued  down,  tape  also  being  glued  over  all  the  rows 
of  tacks  along  the  ribs,  making  a  neat  finish  and  at  the  same  time 
preventing  the  cloth  from  tearing  off  over  the  tack  heads. 

Installation  of  Motor.  As  stated  previously,  the  ideal  motor 
for  a  Bleriot-type  machine  is  short  along  the  crank  shaft,  as  the 
available  space  in  the  fuselage  is  limited,  and  air-cooled  for  the  same 
reason.  Genuine  Bleriots  are  always  fitted  with  one  of  the  special 
types  of  radial  or  rotary  aeronautic  motors,  which  are  always  air- 
cooled.  Next  in  popularity  to  these  is  the  two-cylinder,  horizontal- 
opposed  motor,  either  air-  or  water-cooled.  However,  successful 
machines  have  been  built  with  standard  automobile-type,  four- 
cylinder,  water-cooled  motors,  and  with  four-cylinder,  two-cycle, 
aeronautic  motors. 

When  the  motor  is  water-cooled,  there  will  inevitably  be  some 
difficulty  in  finding  room  for  a  radiator  of  sufficient  size.  One  scheme 
is  to  use  twin  radiators,  one  on  each  side  of  the  fuselage,  inside  of 
the  main  frame  of  the  running  gear.  Another  plan  is  to  place  the 
radiator  underneath  the  fuselage,  using  a  supplementary  water  tank 
above  the  cylinders  to  facilitate  circulation.  These  two  seem  to  be 
about  the  only  practicable  arrangements,  as  behind  the  motor  the 
radiator  would  not  get  enough  air,  and  above  it  would  obstruct  the 
view  of  the  operator. 

It  is  impossible  to  generalize  to  much  effect  about  the  method 
of  supporting  the  motor  in  the  fuselage,  as  this  must  differ  with  the 
motor.  Automobile-type  motors  will  be  carried  on  two  heavy  ash 
beams,  braced  by  lengths  of  steel  tubing  of  about  1  inch  diameter  and 
16  gauge.  When  the  seven-cylinder  rotary  Gnome  motor  is  used, 
the  crank  shaft  alone  is  supported;  it  is  carried  at  the  center  of  two 
X-shaped  frames  of  pressed  steel,  one  in  front  of  and  the  other  behind 
the  motor.  The  three-cylinder  Anzani  motors  are  carried  on  four 
lengths  of  channel  steel  bent  to  fit  around  the  upper  and  lower  por- 
tions of  the  crank  case,  which  is  of  the  motorcycle  type. 

Considerable  care  should  be  taken  to  prevent  the  exhaust  from 
blowing  back  into  the  operator's  face  as  this  sometimes  carries  with 
it  drops  of  burning  oil,  besides  disagreeable  smoke  and  fumes.  The 


649 


84          BUILDING  AND  FLYING  AN  AEROPLANE 

usual  plan  is  to  arrange  a  sloping  dashboard  of  sheet  aluminum  so 
as  to  deflect  the  gases  down  under  the  fuselage. 

The  three  sections  of  the  fuselage  back  of  the  engine  section  are 
usually  covered  on  the  sides  and  bottom  with  cloth  like  that  used 
on  the  wings.  Sometimes  sheet  aluminum  is  used  to  cover  the 
section  between  the  wing  beams.  However,  those  who  are  just 
learning  to  operate  machines  and  are  a  little  doubtful  about  their 
landings  often  leave  off  the  covering  in  order  to  be  able  to  see  the 
ground  immediately  beneath  their  front  wheels. 


Fig.  35.     Running  Gear  of  Morane  Type  of  Bleriot  Monoplane 

New  Features.  Morane  Landing  Gear.  Although  the  regular 
Bleriot  landing  gear  already  described,  has  many  advantages  and 
has  been  in  use  with  only  detail  changes  for  several  years,  some 
aviators  prefer  the  landing  gear  of  the  new  Morane  monoplane, 
which  in  other  respects  closely  resembles  the  Bleriot.  This  gear, 
Fig.  35,  is  an  adaptation  of  that  long  in  use  on  the  Henri  Farman 
and  Sommer  biplanes,  combining  skids  and  wheels  with  rubber-band 
springs.  In  case  a  wheel  or  spring  breaks,  whether  due  to  a  defect 
or  to  a  rough  landing,  the  skids  often  save  an  upset.  Besides,  the 


650 


BUILDING  AND  FLYING  AN  AEROPLANE  85 

tension  of  the  springs  is  usually  such  that  on  a  rough  landing  the 
wheels  jump  up  and  allow  the  skids  to  take  the  shock;  this  also 
prevents  the  excessive  rebound  of  the  Bleriot  springs  under  similar 
conditions. 

Another  advantage  which  may  have  some  weight  with  the 
amateur  builder,  is  that  the  Morane  running  gear  is  much  cheaper 
and  easier  to  construct.  Instead  of  the  two  heavy  tubes,  the  four 
forks  of  oval  tubing,  and  the  many  slides,  collars,  and  blocks — most 
of  them  special  forgings  or  castings — the  Morane  gear  simply  requires 
two  short  laminated  skids,  four  ash  struts,  and  some  sheet  steel. 

The  laminated  skids  are  built  up  of  three  boards  each  of  f- 
by  2-inch  ash,  3J  feet  long.  These  must  be  glued  under  heavy 
pressure  in  forms  giving  the  proper  curve  at  the  front  end.  When 
they  are  taken  from  the  press,  three  or  four  J-inch  holes  should  be 
bored  at  equal  distances  along  the  center  line  and  wood  pins  driven 
in;  these  help  in  retaining  the  curve.  The  finished  size  of  the  skids 
should  be  If  by  If  inches. 

Four  ash  struts  1J  by  2J  inches  support  the  fuselage.  They 
are  rounded  off  to  an  oval  shape  except  at  the  ends,  where  they 
are  attached  to  the  skids  and  the  fuselage  beams  with  clamps  of 
i^-inch  sheet  steel.  The  ends  of  the  struts  must  be  beveled  off 
carefully  to  make  a  good  fit;  they  spread  out  15  degrees  from  the 
vertical,  and  the  rear  pair  have  a  backward  slant  of  30  degrees  from 
vertical. 

Additional  fuselage  struts  must  be  provided  at  the  front  end  of 
the  fuselage  to  take^the  place  of  the  struts  and  beams  of  the  Bleriot 
running  gear.  The  two  vertical  struts  at  the  extreme  front  end  may 
be  of  the  same  1J-  by  2J-inch  ash  used  in  the  running  gear,  planed 
down  to  1^  inches  thick  to  match  the  thickness  of  the  fuselage 
beams.  The  horizontal  struts  should  be  !£•  by  If  inches. 

The  wheels  run  on  the  ends  of  an  axle  tube,  and  usually  have 
plain  bearings.  The  standard  size  bore  of  the  hub  is  f|  inch,  and 
the  axle  tube  should  be  yf  inch  diameter  by  11  gauge.  The  tube 
also  has  loosely  mounted  on  it  two  spools  to  carry  the  rubber  band 
springs.  These  are  made  of  2|-inch  lengths  of  If -inch  tubing,  with 
walls  of  sufficient  thickness  to  make  an  easy  sliding  fit  on  the  axle 
tube.  To  the  ends  of  each  length  of  tube  are  brazed  2J-inch  washers 
of  A-inch  steel,  completing  the  spool. 


651 


86 


BUILDING  AND  FLYING  AN  AEROPLANE 


The  ends  of  the  rubber  bands  are  carried  on  rollers  of  f-inch, 
16-gauge  tubing,  fastened  to  the  skids  by  fittings  bent  up  from 
j^-inch  sheet  steel.  Each  fitting  is  bolted  to  the  skid  with  two 
f-inch  bolts. 

Some  arrangement  must  now  be  made  to  keep  the  axle  centered 
under  the  machine,  as  the  rubber  bands  will  not  take  any  sidewise 
strain.  A  clamp  of  heavy  sheet  steel  should  be  made  to  fit  over  the 
axle  at  its  center,  and  from  this  heavy  wires  or  cables  run  to  the 
bottom  ends  of  the  forward  struts.  These  wires  may  be  provided 
with  stiff  coil  springs,  if  it  is  desired  to  allow  a  little  sidewise  move- 
ment. 

New  Bleriot  Inverse  Curve   Tail.     Some  of  the  latest  Bleriot 


Fig.   30.      Details  of  Bleriot  inverse  Curve  Tail 

machines  have  a  new  tail  which  seems  to  add  considerable  to  their 
speed.  It  consists  of  a  fixed  tail,  Fig.  36,  nearly  as  large  as  the 
old-style  tail  and  elevators  combined,  with  two  elevator  flaps  hinged 
to  its  rear  edge.  The  peculiarity  of  these  elevators,  from  which  the 
tail  gets  its  name,  is  that  the  curve  is  concave  above  and  convex 
below — at  first  glance  seeming  to  have  been  attached  upside  down. 
In  this  construction,  the  1-inch,'  20-gauge  tube,  which  formerly 
passed  through  the  center  of  the  tail,  now  runs  along  the  rear  edge, 
being  held  on  by  strips  of  \-  by  r^-inch  steel  bent  into  U -shape 
and  fastened  with  screws  or  bolts  to  the  ribs.  Similar  strips  attach 
the  elevators  to  the  tube,  but  these  strips  are  bolted  to  the  tube. 


653 


BUILDING  AND  FLYING  AN  AEROPLANE  87 

The  construction  is  otherwise  like  that  previously  described.  It  is 
said  that  fitting  this  tail  to  a  Bleriot  in  place  of  the  old-style  tail 
adds  5  miles  an  hour  to  the  speed,  without  any  other  changes  being 
made. 

Another  slight  change  which  distinguishes  the  newer  Bleriots  is 
in  the  overhead  frame,  which  now  consists  of  a  single  inverted  V 
instead  of  two  V's  connected  by  a  horizontal  tube.  The  single  V 
is  set  slightly  back  of  the  main  wing  beam,  and  is  higher  and,  of 
course,  of  heavier  tubing  than  in  the  previous  construction.  Its  top 
should  stand  2  feet  6  inches  above  the  fuselage,  and  the  tubing 
should  be  1  inch  18  gauge.  It  also  requires  four  truss  wires,  two 
running  to  the  front  end  of  the  fuselage  and  two  to  the  struts  to 
which  the  rear  wing  beams  are  attached.  All  of  the  wires  on  the 
upper  side  of  the  wings  converge  to  one  point  at  the  top  of  this  V, 
the  wires  from  the  wing  beams,  of  course,  passing  over  pulleys. 

These  variations  from  the  form  already  described  may  be  of 
interest  to  those  who  wish  to  have  their  machines  up-to-date  in 
every  detail,  but  they  are  by  no  means  essential.  Hundreds  of  the 
old-style  Bleriots  are  flying  every  day  and  giving  perfect  satisfaction. 

ART  OF  FLYING 

Knowledge  of  the  science  of  aeronautics  and  ability  to  fly  are 
two  totally  different  things.  Long-continued  study  of  the  problem 
from  its  scientific  side  enabled  the  Wright  Brothers  to  learn  how 
to  build  a  machine  t{iat  would  fly,  but  it  did  not  teach  them  how  to 
fly  with  it.  That  came  as  the  result  of  persistent  attempts  at 
flying  itself.  A  study  of  the  theoretic  laws  of  balancing  does'  not 
form  a  good  foundation  for  learning  how  to  ride  a  bicycle — practice 
with  the  actual  machine  is  the  only  road  to  success.  The  best  evi- 
dence of  this  is  to  be  found  in  the  fact  that  several  of  the  most  suc- 
cessful aviators  today  have  but  a  slight  knowledge  of  the  science  of 
aeronautics.  They  are  not  particularly  well  versed  in  what  makes 
flight  possible,  but  they  know  how  to  fly  because  they  have  learned 
it  in  actual  practice. 

Reference  to  the  early  work  of  the  Wright  Brothers  shows  that 
during  a  period  of  several  years  they  spent  a  large  part  of  their  time 
in  actual  experiments  in  the  air,  and  it  was  not  until  these  had  proved 


653 


88 


BUILDING  AND  FLYING  AN  AEROPLANE 


entirely  satisfactory  that  they  attempted  to  build  a  power-driven 
machine. 

Methods  Used  in  Aviation  Schools.     Aviation  schools  are  spring- 
ing up  all  over  this  country  and  there  are  a  number  of  well-established 


Fig.  37.     Monoplane  Dummy  Used  for  Practice  in  Aviation  Schools 

institutions  of  this  kind  abroad.  In  the  course  of  instruction,  the 
student  must  first  learn  the  use  of  the  various  controls  on  a  dummy 
machine.  In  the  case  of  an  English  school,  this  dummy,  Fig.  37,  is 
a  motorless  aeroplane  mounted  on  a  universally-jointed  support  so 


Fig.  38.     Aerocycle  with  Treadle  Power  for  Practice  Work 

as  to  swing  about  a  pivot  as  desired.  This  is  employed  for  the  pur- 
pose of  familiarizing  the  beginner  with  the  means  of  maintaining 
equilibrium  in  the  air. 


654 


BUILDING  AND  FLYING  AN  AEROPLANE 


89 


A  French  school,  on  the  other  hand,  employs  a  wingless  machine, 
which  is  otherwise  complete,  as  it  consists  of  a  regulation  chassis 
with  motor  and  propeller,  all  steering  and  elevating  controls.  On 
this,  the  student  may  practice  what  has  come  to  be  familiarly  known 
as  "grass-cutting,"  to  his  heart's  content,  without  any  danger  of 
the  machine  taking  to  the  air  unexpectedly,  as  has  frequently  been  the 
case  where  first  attempts  have  been  made  on  a  full-fledged  machine. 
Usually,  most  of  such  attempts  result  disastrously,  often  destroying 
in  a  moment  the  result  of  months  of  work  in  building  the  machine. 


Fig.  39.     Voisin  Biplane  with  Double  Control  for  Teaching  Beginners 

A  French  aerocycle,  Fig.  38,  a  comparatively  inexpensive  machine, 
is  also  useful  for  practice  in  balancing  and  in  short,  low  flights.  The 
French  apparatus  in  question  may  accordingly  be  considered  an 
advance,  not  only  over  the  English  machine,  even  of  the  type  shown 
in  Fig.  39,  which  has  a  double  control,  and  is  especially  designed  for 
the  teaching  of  beginners,  but  very  much  over  the  practice  of  attempt- 
ing to  actually  fly  for  the  first  time  in  a  strange  machine,  as  it  pro- 
vides the  necessary  practice  in  the  handling  of  the  motor  and  the 
lateral  steering.  The  machine  can  make  high  speed  over  the  ground, 


655 


90  BUILDING  AND  FLYING  AN  AEROPLANE 

but  is  perfectly  safe  for  the  beginner,  as  it  is  incapable  of  rising.  Hav- 
ing gone  through  the  stages  represented  by  either  of  these  con- 
trivances, the  best  course  for  the  learner  to  follow  is  to  try  gliding, 
taking  short  glides  to  attain  the  ability  to  quickly  meet  varying  con- 
ditions of  the  atmosphere. 

The  fact  that  these  glides  are  of  extremely  short  duration  at  first 
need  not  be  discouraging  when  it  is  recalled  that,  after  several  years 
of  work,  the  Wright  Brothers  considered  that  great  progress  had 
been  made  when,  in  1902,  they  were  able  to  make  glides  of  26  seconds. 
During  six  days  of  the  practice  season  of  that  year,  they  made  375 
gliding  flights  of  various  distances,  most  of  them  comparatively 
short,  but  each  one  of  value  in  familiarizing  the  glider  with  the  con- 
ditions to  be  met.  It  is  not  material  whether  gliding  or  manipulation 
of  the  control  levers  is  taken  up  first,  as  both  should  be  mastered  as 
far  as  possible  before  attempting  to  fly  a  regular  machine. 

Use  of  the  Elevating  Plane.  So  many  things  are  necessary  to 
the  control  of  an  aeroplane  that  thinking  becomes  entirely  too  slow 
a  process — the  aviator  must  be  endowed  with  something  approaching 
the  instinct  of  the  bird;  he  must  be  so  familiar  with  his  machine  and 
its  peculiarities  that  a  large  part  of  the  work  of  controlling  it  is  the 
result  of  subconscious  movement.  The  control  levers  of  many 
machines  are  so  arranged  that  this  subconscious  movement  on  the 
part  of  the  aviator  directly  operates  the  balancing  mechanism. 
There  is  no  time  to  think.  When  a  machine  rises  from  the  ground, 
facing  the  wind  as  it  should,  its  path  of  flight  should  be  a  gradual 
upward  inclination,  this  being  something  difficult  to  accomplish  at 
first,  owing  to  the  sensitiveness  of  the  elevating  rudder,  the  tendency 
almost  invariably  being  to  give  the  latter  too  great  an  angle  of 
incidence.  At  this  stage,  the  maximum  velocity  of  flight  has  not  yet 
been  attained  and  care  must  be  taken  to  keep  the  angle  of  ascent 
small.  Otherwise,  the  power  of  the  engine,  which  may  not  have 
reached  its  maximum,  would  not  be  sufficient  to  cause  the  machine 
to  ascend  an  inclined  path  at  the  starting  speed.  If  the  speed  of 
flight  be  reduced  by  the  increased  resistance  at  this  point,  the  whole 
machine  will  slide  back  in  the  air,  and  if  a  sudden  gust  of  wind  happens 
to  coincide  with  the  attempt  to  rise  at  too  great  an  angle,  there  is 
danger  of  it  being  blown  over  backward. 

Where  the  machine  is  just  leaving  the  ground  and  the  elevator 


656 


BUILDING  AND  FLYING  AN  AEROPLANE  91 

has  been  set  at  an  excessive  angle,  the  rear  end  of  the  skids  or  the 
tail  may  slap  the  ground  hard  and  break  off,  or  they  will  impose  so 
much  resistance  upon  its  movement  by  scraping  over  the  turf  that 
the  machine  can  not  attain  its  soaring  speed.  It  must  be  borne  in 
mind,  of  course,  that  remarks  such  as  the  present  can  be  only  of  the 
most  general  nature,  every  type  of  machine  having  its  own  peculiar- 
ities— in  some  instances,  the  extreme  opposite  of  those  characterizing 
similar  machines.  For  example,  in  the  Voisin  1910  type,  the  very 
large  and  powerful  light  tail  tends  to  lift  before  the  main  planes, 
and  if  this  be  not  counteracted,  the  whole  machine  may  turn  up  on 
its  end.  In  order  to  offset  this  tendency,  the  elevator  must  be  raised 
so  as  to  keep  sufficient  pressure  beneath  it;  the  moment  of  this  pres- 
sure about  the  center  of  gravity  must  be  at  least  equal  to  the  pressure 
under  the  tail  planes  about  the  center  of  gravity  of  the  machine,  or 
the  tail  will  rise  unduly  in  the  air.  At  least  that  is  the  theory  of  it — 
naturally,  only  practice  with  that  particular  machine  would  suffice 
to  enable  an  aviator  to  familiarize  himself  with  that  particular 
peculiarity.  Again,  some  machines  are  "tail  heavy."  But  there  is 
great  difficulty  in  even  approximating  the  degree  of  relative  motion, 
for  which  reason  it  has  been  suggested,  under  "Accidents  and  Their 
Lessons,"  that  a  gradometer,  or  small  spirit  level,  in  plain  sight  of 
the  aviator,  should  form  part  of  the  equipment  of  every  machine. 
The  Wrights  long  ago  adopted  the  expedient  of  attaching  a  strip  of 
ribbon  to  the  elevator  to  provide  an  indication  of  motion  relative 
to  the  wind. 

Aeroplane  in  Fligjit.  The  sensation  of  motion  after  the  machine 
leaves  the  ground  is  almost  imperceptible,  and  it  is  likewise  extremely 
difficult  to  tell  at  just  what  moment  the  aeroplane  ceases  running 
on  the  solid  ground  and  takes  to  the  air.  There  is  a  feeling  of  exhilara- 
tion but  very  little  of  motion.  Whereas  40  miles  an  hour  over  the 
ground,  particularly  in  an  automobile,  brings  with  it  a  lively  appre- 
ciation of  the  speed  of  travel,  the  same  speed  in  an  aeroplane  is  a 
very  gentle  motion  when  high  above  the  ground.  If  there  be  no 
objects  close  at  hand,  with  which  to  compare  the  speed,  the  sense  of 
motion  is  almost  entirely  lost. 

Center  of  Gravity.  The  static  balance  of  a  machine  should  be 
carefully  tried  before  commencing  to  fly,  and  particularly  that  of  a 
biplane  of  the  Wright  type,  in  which  the  aviator  sits  beside  the  engine. 


657 


92  BUILDING  AND  FLYING  AN  AEROPLANE 

When  provision  is  made  for  carrying  a  passenger,  his  seat  is  placed 
in  the  center  line  of  the  machine,  so  that  his  presence  or  absence 
does  not  materially  affect  the  question  of  lateral  balance.  As  men 
are  not  all  of  the  same  weight,  in  cases  in  which  the  aviator  only 
partly  balances  the  engine  about  the  center  line,  his  weight  being 
insufficient  for  the  purpose,  extra  weights  should  be  placed  on  the 
wing  tip  at  the  lightest  end  until  the  true  balance  is  secured,  other- 
wise a  permanent  warping,  or  gauchissement  as  the  French  term  it, 
is  required  at  this  side  in  order  to  keep  the  machine  on  an  even  keel. 
In  other  words,  the  machine  will  carry  what  sailors  term  a.  port  helm 
where  the  left  side  of  the  machine  is  lighter  than  the  right,  and  vice 
versa,  and  it  will  be  necessary  to  keep  the  rudder  over  to  that  side 
slightly  during  the  entire  flight  to  counteract  this  tendency. 

In  aeroplanes  fitted  with  tails,  the  center  of  gravity  is  usually 
in  the  vicinity  of  the  trailing  edge  of  the  main  planes  and,  of  course, 
should  be  on  the  center  line  of  the  machine.  The  center  of  gravity 
of  the  aviator  on  a  monoplane  should  approximately  coincide  with 
that  of  the  machine.  If  this  be  not  the  case,  the  stabilizers  or  the 
elevator  must  be  permanently  set  to  produce  longitudinal  balance. 
Much  downward  set,  or  the  increase  of  the  angle  of  incidence  of  the 
tail,  will  create  undue  resistance  to  flight  and  should  be  avoided  when 
possible  by  bringing  the  weight  farther  forward.  The  center  of  pres- 
sure should  coincide  with  the  center  of  gravity,  and  balance  will 
result. 

Before  even  ground  work  is  attempted,  the  position  of  the 
center  of  gravity  should  be  determined  in  the  manner  shown  in  Fig. 
40,  the  approximate  location  for  four  types  of  machines  being  shown. 
At  what  point  the  machine  must  be  suspended,  so  that  it  can  tip  only 
frontward  and  backward  and  be  evenly  balanced,  is  a  question  that 
must  be  answered  in  order  to  ascertain  the  probability  of  the  machine's 
pitching  forward  whenever  mud,  grass,  or  rough  ground  is  encoun- 
tered in  alighting.  If  the  center  of  gravity  should  lie  in  front  of  the 
axles  of  the  ground  wheels  in  a  machine  of  the  Farman  type,  trouble 
is  sure  to  follow.  Always  consider  the  relation  of  the  center  of  gravity 
to  the  wheels,  in  order  that  you  may  gain  some  idea  of  the  distribu- 
tion of  the  weight  on  the  running  gear  when  the  machine  is  tipped 
forward  10  degrees.  If  the  wheels  are  not  forward  far  enough  there 
will  be  trouble  in  running  on  the  ground.  The  elevators  must  correct 


658 


BUILDING  AND  FLYING  AN  AEROPLANE 


93 


whatever  variance  there  may  be  from  the  correct  center  of  gravity 
and  position  of  the  wheels,  and  the  manipulation  of  the  elevators  for 
.that  purpose  requires  skill.  If  the  tail  be  very  heavy,  the  elevator 
may  not  be  able  to  counteract  that  defect. 

The  position  of  the  center  of  gravity  of  a  machine  in  regard  to 
lateral  stability  in  flight  is  a  matter  of  far  greater  importance  than 
untried  aviators  realize.  Having  it  too  low  is  quite  as  bad  as  too  high, 
as  in  either  case  there  is  a  tendency  to  upset.  Although  the  dihedral 
angle  is  considered  wasteful  of  power,  it  seems  to  do  more  to  secure 
inherent  stability  than  any  other  device.  Devices  for  maintaining 
stability  automatically  are  to  be  frowned  upon  in  the  present  state 


GftOL/ND  L/ME\ 


(c) 


L/NE\ 


Fig.  40.      Method  of  Determining  Center  of  Gravity  of  Different  Types  of  Machines 

of  the  art.  The  sensitive  perception  and  quick  response  which  come 
with  intimate  knowledge  of  a  machine's  peculiarities,  are  at  present 
worth  more  than  gyroscopes  and  pendulums.  To  acquire  this 
intimate  knowledge,  the  aviator  must  familiarize  himself  thoroughly 
with  the  machine;  he  must  become  so  accustomed  to  controls  that 
he  and  the  machine  are  literally  one.  A  practiced  bicycle  rider  does 
not  have  to  think  about  balance,  neither  does  the  practiced  aviator, 
yet  he  must  always  be  prepared  to  meet  motor  stoppages,  unusual 
air  disturbances,  and  breakages.  A  leap  from  the  ground  directly 
into  the  air,  without  preliminary  practice,  means  certain  accident, 
to  put  it  mildly. 


659 


94          BUILDING  AND  FLYING  AN  AEROPLANE 

Center  of  Pressure.  But  although  the  center  of  gravity  remains 
approximately  constant,  the  center  of  pressure  is  continually  vary- 
ing and  is  never  constant  for  many  seconds.  The  center  of  pressure 
on  an  aerocurve  constructed  to  Phillips'  design,  Fig.  41,  is  about 
one-third  of  the  chord  from  the  leading  edge  of  the  plane  under  normal 
conditions,  i.  e.,  when  the  angle  of  incidence  is  about  8  degrees  between 
the  direction  of  motion  of  the  plane  and  that  of  the  air.  At  the 
moment  this  angle  is  increased  the  center  of  pressure  moves  toward 
the  rear,  and  vice  versa.  The  center  of  gravity  must  be  moved  to 
coincide  with  this  new  position,  or  the  center  of  pressure  must  be 
artificially  restored  by  the  use  of  supplementary  planes  or  elevators, 
moving  in  a  contrary  direction.  A  forward  movement  of  the  center  of 
pressure  tends  to  lower  the  tail  of  the  machine,  when  the  intensity  of 
the  pressure  is  unchanged,  and  to  counterbalance  this  the  rear  elevator 
must  have  its  angle  of  incidence  increased  in  order  to  increase  the 
lift  at  the  rear  of  the  machine,  or  it  will  slide  down  backward.  The 
alternative  to  be  adopted  in  case  of  temporary  lack  of  engine  power 
is  to  decrease  the  angle  of  the  elevator  and  allow  the  aeroplane  to 
sweep  downward,  thus  gaining  momentum.  The  increase  of  speed 

will  then  be  sufficient  probably 
to  enable  the  machine  to  con- 
tinue in  a  horizontal  flight, 
when  the  center  of  pressure  is 

rig.  4i.  Aerocurve  of  Phillip's  Design  '  '  again  restored  to  its  normal 

position. 

Ground  Practice.  First  of  all,  the  aviator  should  familiarize 
himself  with  his  seat  for  it  is  from  that  place  that  he  must  judge 
wind  effects,  vibration,  motor  trouble,  and  the  thousand  and  one 
little  creaks  and  hums  that  will  ultimately  mean  so  much  to  him. 
Not  until  he  has  thoroughly  accustomed  himself  to  his  seat,  should 
he  try  to  run  along  the  ground.  This  done,  hours  should  be  spent 
running  up  and  down  and  around  the  field  to  learn  the  use  of  the 
rudder,  particularly  on  rough  ground.  The  runs  should  be  straight 
so  that  when  the  time  comes  to  leap  into  the  air,  the  aviator  may  be 
sure  that  he  is  on  an  even  keel,  and  flying  straightaway.  In  order 
to  prevent  the  possibility  of  leaving  the  ground  unexpectedly  in 
practice,  trials  should  be  made  only  in  calm  weather  and  with  the 
motor  well  throttled  down  so  that  the  machine  will  be  reduced  to  a 


660 


BUILDING  AND  FLYING  AN  AEROPLANE  95 

speed  of  not  more  than  15  miles  per  hour.  After  a  time  this  may  be 
increased  to  20,  but  the  latter  is  the  maximum  for  ground  practice, 
as  the  machine  will  rise  at  speeds  slightly  exceeding  this.  In  these 
practice  runs  on  the  ground,  the  student  should  learn  to  gauge  the 
rush  of  air  against  his  face,  as  when  aloft  his  best  gauge  will  be  the 
wind  pressure  on  his  cheeks,  as  that  will  tell  him  whether  he  is  mov- 
ing with  sufficient  speed  to  keep  up  or  not.  It  will  also  tell  him  ulti- 
mately whether  he  is  moving  along  the  ground  fast  enough  to  leap  up. 

In  this  stage  of  experimenting  on  the  ground,  the  elevator  is 
kept  neutral  as  far  as  possible.  With  increasing  skill  its  use  may  be 
ventured,  but  only  sparingly,  for  it  takes  very  little  to  lift  the  machine 
from  the  ground  with  a  speed  in  excess  of  20  miles  per  hour.  It  will 
soon  be  discovered  that  the  elevator  can  be  used  as  a  brake  to  pre- 
vent pitching  forward.  The  tail  elevators  on  the  Farman  or  Bleriot 
running  gear  are  very  effective  owing  to  the  blast  of  the  propeller, 
even  when  the  main  planes  are  not  moving  forward  at  lifting  speed. 
With  the  Curtiss  type  of  running  gear  and  a  front  elevator  only, 
it  is  often  possible  at  18  to  20  miles  per  hour  to  raise  the  front  wheel 
off  the  ground  for  a  second  or  two — facts  which  indicate  that  at  25 
to  28  miles  per  hour,  the  elevator  is  far  more  effective. 

First  Flight.  The  first  actual  flight  should  be  confined  to  a  short 
trip  parallel  to  the  ground  and  not  more  than  one  or  two  feet  above 
it.  At  first,  the  student  should  see  how  close  he  can  fly  to  the  ground 
without  actually  touching  it,  which  he  can  do  by  gradually  increas- 
ing his  forward  speed.  This  must  be  done  in  an  absolute  calm  as  an 
appreciable  amount  of  wind  will  bring  in  too  many  other  factors  for 
the  student  to  master  at  so  early  a  stage.  This  practice  should  be 
continued  in  calm  air  until  short,  straight  flights  can  be  made  a  foot 
or  two  from  the  ground  with  the  motor  wide  open.  If  it  be  found 
that  the  machine  barely  flies  straightaway  with  the  full  power  of  the 
motor,  the  latter  is  either  badly  out  of  adjustment,  or  a  more  power- 
ful engine  is  required.  In  an  under-powered  machine  turning  would 
be  suicidal.  Moreover,  the  resistance  encountered  in  the  air  is 
greater  than  on  the  ground  and  may  be  such  that  the  speed  is  not 
sufficient  for  sustentation.  Fig.  42,  (a)  and  (b),  show  why  it  is  possible 
to  run  along  the  ground  faster  than  it  is  possible  to  travel  in  the  air, 
under  certain  conditions,  and  why  the  ground  can  be  left  at  low 
speed.  If  it  were  possible  to  drive  a  machine  with  such  enormous 


661 


96          BUILDING  AND  FLYING  AN  AEROPLANE 

projected  areas  as  BB,  shown  in  Fig.  42  (b),  a  man  could  fly  slowly  for 
an  indefinite  period.  But  the  projected  area  is  greater  than  the  air 
displaced  by  the  propeller,  and  it  is  impossible  to  fly  except  with  a 
moderate  angle  of  incidence,  giving  projected  areas  A  A,  Fig.  42  (a). 
The  student,  as  he  increases  in  skill,  may  venture  to  a  height  of 
10  feet,  which  should  be  maintained  as  accurately  as  before,  and 
after  making  a  run  of  100  yards,  the  machine  should  be  pointed 
down,  but  ever  so  slightly.  The  wind  pressure  on  the  face  immediately 
becomes  greater.  Within  a  foot  or  two  of  the  ground  the  motor 
should  be  cut  off  or  throttled.  This  should  be  tried  ten  or  fifteen 
times,  and  the  height  increased  to  30  or  40  feet,  in  order  that  the 
student  may  familiarize  himself  with  the  sensation  of  coasting.  At 
the  end  of  each  glide  the  machine  will  seem  to  become  more  responsive, 
as  indeed  it  does,  for  gliding  down  greatly  increases  the  efficiency 
of  the  elevator  and  other  controls,  because  of  the  increased  speed. 
Gliding  down  steep  angles  is  often  the  aviator's  salvation  in  a  tight 


Fig.  42.      Diagrams   Showing   Greater  Projected   Area  of   Main  Plane  when 
Running  along  Ground 

place,  particularly  when  the  motor  fails,  a  side  gust  threatens,  or 
an  air  pocket  is  encountered. 

Warping  the  Wings.  When  sufficient  confidence  has  been 
attained  at  a  height  of  30  to  40  feet,  the  ailerons  or  warping  devices 
may  be  tried  judiciously.  Here  the  intention  should  be  to  correct 
any  tendency  to  side  tipping,  and  not  purposely  to  incline  the  machine 
as  far  as  possible  without  actually  causing  a  wreck.  The  use  of  the 
lateral  control  may  cause  the  machine  to  swerve  a  little,  but  that 
may  be  ignored.  Before  landing,  a  straight  course  should  be  taken 
so  that  the  machine  will  always  come  down  on  an  even  keel.  With 
increasing  practice,  the  student  may  fly  higher,  but  always  with  the 
understanding  that  there  is  a  limit  to  the  angle  of  incidence.  An 
automobile  is  retarded  when  it  strikes  a  short,  steep  hill;  so  is  an 
aeroplane.  No  aeroplane  has  yet  been  built  that  can  take  a  steep 
angle  and  climb  right  up  that  grade  continuously.  Altitude  is 


662 


BUILDING  AND  FLYING  AN  AEROPLANE          97 

reached  by  a  series  of  small  steps  and  at  comparatively  low  angles, 
as  unless  the  course  is  straightened  out  at  regular  intervals,  a  machine 
will  lose  its  speed  and  tend  to  plunge  tail  first,  just  as  is  the  case  when 
an  attempt  is  made  to  rise  from  the  ground  at  too  sharp  an  angle. 

In  warping  the  wings  an  increase  of  lift  imparted  to  one  wing 
of  the  machine  is  produced  by  increasing  the  angle  of  incidence  of 
the  whole  or  part  of  the  wing,  or  by  an  increase  of  pressure  under 
that  wing,  and  will  tend  to  cause  that  side  of  the  machine  to  rise 
and  the  other  side  to  lower,  the  result  being  that  the  machine  will 
be  liable  to  slide  through  the  air  diagonally.  In  the  majority  of 
aeroplanes  there  are  no  fins  or  keels  to  counteract  this  movement, 
and  lateral  stability  must  be  restored  by  artificially  increasing  the 
lift  of  the  depressed  wing.  This  can  be  done  by  warping,  or  lowering 
the  trailing  edge  of  the  depressed  wing  and  increasing  its  lift,  and 
simultaneously  raising  the  trailing  edge  of  the  other  wing,  thus 
decreasing  the  angle  of  incidence  of  the  latter  and  reducing  its  lifting 
effect.  This  applies  to  flight  on  a  straight  course,  whatever  the  cause 
may  be  that  tends  to  upset  lateral  stability.  It  will  be  seen,  there- 
fore, that  the  center  of  gravity  remains  constant  and  the  center  of 
pressure  must  be  manipulated  to  restore  stability.  This  manipula- 
tion is  much  more  rapid  and  positive  than  the  alteration  of  the  center 
of  gravity  by  the  movement  of  the  aviator's  body  resorted  to  in  the 
early  gliding  flights  of  pioneer  experimenters. 

Making  a  Turn.  The  first  turn  should  be  made  over  a  large 
field  and  the  diameter  of  the  turn  should  be  at  least  half  a  mile.  The 
height  should  be  no^  less  than  50  feet.  After  that  level  has  been 
maintained,  the  rudder  should  be  moved  very  gingerly.  The  machine 
will  lean  in  almost  immediately,  because  the  outer  end  travels  at  a 
higher  speed  than  the  inner  and  therefore  has  a  greater  lift.  Warping 
or  working  the  ailerons  should  be  resorted  to  as  a  means  of  counter- 
acting this  tendency,  and  the  rudder  swung  to  the  opposite  direc- 
tion, if  necessary.  It  is  obvious  that  if  the  rudder  will  cause  the 
machine  to  bank  when  swung  in  one  direction,  it  will  right  the  machine 
again  when  swung  in  the  opposite  direction.  It  is  even  possible  to 
turn  the  machine  on  an  even  keel  by  anticipating  the  banking,  simply 
by  correctly  using  the  rudder,  which  was  necessary  in  the  old  Voisin 
machine  flown  by  Farman  in  1908,  because  it  had  no  mechanical 
lateral  control.  The  student  should  learn  the  correct  angle  of  bank- 


663 


98  BUILDING  AND  FLYING  AN  AEROPLANE 

ing,  i.  e.,  the  angle  at  which  the  machine  will  neither  skid  nor  slide 
down  and  which  is  most  economical  of  power  because  it  requires 
less  use  of  the  lateral  controls.  The  necessity  of  "feeling  the  air" 
is  greater  in  turning  than  in  any  other  phase  of  flying.  By  "feeling 
the  air"  is  meant  the  ability  to  meet  any  contingency  intuitively 
and  not  until  this  is  acquired  can  the  student  become  an  expert 
aviator.  When  it  has  been  acquired,  safe  flying  is  assured  and  is 
dependent  only  upon  the  integrity  of  the  planes,  motor,  and  controls. 
By  using  the  rudder  discreetly  and  by  banking  simply  far  enough 
to  partially  offset  the  centrifugal  force  of  turning,  the  use  of  the 
lateral  control  will  not  be  necessary  in  still  air.  Even  too  short  a 
turn  can  be  corrected  by  a  quick  use  of  the  rudder. 

The  peculiarities  existing  between  different  types  of  mono- 
planes become  even  more  marked  than  between  the  biplane  and  the 
monoplane.  For  example,  in  piloting  a  Bleriot  monoplane,  Fig. 
43,  it  is  necessary  to  take  into  account  the  effect  of  the  engine  torque. 
As  the  engine  rotates  in  a  right-hand  direction,  from  the  point  of 
view  of  the  pilot,  the  left  wing  tends  to  rise  in  the  air,  owing  to  the 
depression  of  the  right  side  of  the  machine.  The  machine  also  tends 
to  turn  to  the  right,  and  this  must  be  counteracted  by  putting  the 
rudder  over  to  the  left.  An  aeroplane  answers  its  controls  with  com- 
parative slowness,  with  the  exception,  perhaps,  of  the  Wright  machine, 
which  is  noted  for  its  sensitive  and  quick  response  to  every  move- 
ment of  the  levers.  All  control  movements  must,  therefore,  be  very 
gentle,  as  the  behavior  of  an  aeroplane  is  more  like  that  of  a  boat 
than  that  of  an  automobile.  The  action  of  the  elevator  has  already 
been  described,  and  it  is,  perhaps,  the  most  difficult  of  all  the  con- 
trols to  manipulate,  in  that  it  requires  the  exercise  of  a  new  sense. 
The  direction  rudder  is  naturally  a  more  familiar  type  of  control, 
and  in  action  is  similar  to  the  rudder  of  a  boat. 

The  torque  of  the  motor  renders  it  advisable  for  a  novice  to 
turn  his  machine  to  the  right,  if  a  right-hand  propeller  be  used,  and 
vice  versa.  If  two  propellers,  turning  in  opposite  directions,  are 
employed,  as  in  the  Wright  biplane,  there  is  no  inequality  from  the 
torque  of  the  motor.  Since  torque  is  not  noticeable  in  straight  fly- 
ing, straightening  out  again  will  always  serve  the  student  when  he 
finds  himself  in  trouble  on  a  turn.  When  the  use  of  the  rudders 
and  ailerons  has  reduced  the  speed,  a  downward  glide  will  increase 


664 


BUILDING  AND  FLYING  AN  AEROPLANE 


99 


665 


100         BUILDING  AND  FLYING  AN  AEROPLANE 

I 
it  again,  and  if  the  motor  should  stop  on  a  turn,  such  a  downward 

glide  is  immediately  imperative.  When  the  machine  is  thus  gliding, 
a  change  in  the  fore-and-aft  balance  becomes  at  once  apparent, 
because  the  blast  of  the  propeller  no  longer  acts  on  the  tail,  and  the 
elevator  must  then  be  used  with  greater  amplitude  to  obtain  the 
same  effect. 

Only  by  constant  practice  in  calm  air  can  the  student  familiarize 
himself  with  exactly  the  amount  of  warping  and  rudder  control  to 
employ  to  properly  offset  the  lowering  of  the  inner  wing  in  rounding 
a  turn.  If  this  be  not  corrected,  the  whole  machine  tends  to  bank 
excessively  and  will  be  apt  to  slide  downward  in  a  diagonal  direc- 
tion, Fig.  44.  This  is  a  perilous  position  for  the  aviator  and  must 
be  guarded  against  by  the  manipulation  of  the  warping  control  so 
as  to  increase  the  lift  of  the  inner  wing  of  a  biplane,  at  the  same  time, 
employing  the  rudder  to  counteract  this  tendency.  The  use  of  the 
rudder  is  of  even  greater  importance  on  the  monoplane,  as,  in  this 
case,  warping  the  inner  wing  tends  to  direct  the  whole  machine 
downward  instead  of  raising  the  inner  wing  itself.  Several  bad 
accidents  have  resulted  from  monoplanes  refusing  to  respond  to  the 
warping  of  the  inner  wing  when  making  a  turn.  In  such  machines, 
the  rudder  must  be  practically  always  employed  in  connection  with 
the  warping  of  the  wings  in  order  to  keep  the  machine  on  an  even 
keel,  although  the  controls  may  not  actually  be  interconnected, 
this  being  one  of  the  grounds  on  which  foreign  manufacturers  are 
trying  to  make  use  of  the  Wright  principle,  without  infringing  the 
Wright  patents,  as  while  they  employ  warping  in  connection  with 
the  simultaneous  use  of  the  rudder,  the  controls  are  not  attached  to 
the  same  lever  as  in  the  Wright  machine. 

Lateral  resistance  must  also  be  taken  into  consideration  in 
turning,  otherwise  the  machine,  if  kept  on  an  even  keel,  will  tend 
to  skid  through  the  air  and  turn  about  its  center  of  gravity  as  a  pivot. 
In  the  case  of  an  automobile,  the  resistance  to  lateral  displacement 
is  great,  though  on  a  greasy  surface  it  may  be  small,  as  when  the 
machine  skids  sideways,  a  suitable  banking  of  the  road  being  neces- 
sary to  prevent  this  on  turns.  Many  hold  that  the  banking  of  the 
aeroplane  on  turns  is  only  the  direct  effect  of  the  turning  itself,  but 
the  fallacy  of  this  wTill  be  apparent  upon  a  consideration  of  the  law 
of  centrifugal  force.  It  is  obvious  that  to  make  a  turn,  some  force 


666 


BUILDING  AND  FLYING  AN  AEROPLANE 


101 


667 


102         BUILDING  AND  FLYING  AN  AEROPLANE 

must  be  imparted  to  the  machine  to  counteract  the  effect  of  the  cen- 
trifugal force  upon  the  machine  as  a  whole.  And  as  the  sidewise 
projection  of  the  machine  is  small,  a  compensating  force  must  be 
introduced.  This  can  be  done  only  by  previously  banking  up  the 
machine  on  the  outer  wing,  so  that  the  pressure  of  the  air  under  the 
main  plane  can  counteract  the  tendency  to  lateral  displacement. 
The  force  then  acting  under  the  planes  is  in  a  diagonal  direction, 
and  the  angle  at  which  it  is  inclined  vertically  depends  upon  the 
banking  of  the  planes,  it  being  normal  to  their  greater  dimension. 
This  force  can  be  resolved  into  two  forces,  one  perpendicular  and  one 
horizontal,  the  magnitude  of  each  being  dependent  upon  the  degree 
of  banking.  When  the  speed  of  the  machine  is  higher,  the  amount 
of  banking  must  be  greater  in  order  to  increase  the  value  of  the  hori- 
zontal component  in  proportion  to  the  increase  of  the  value  of  the 
centrifugal  force  at  the  higher  speed,  in  spite  of  the  fact  that  the 
forces  acting  under  the  planes  are  also  greater  due  to  the  higher 
speed. 

As  the  curve  commences,  the  rudder  being  put  over,  the  difference 
of  the  pressures  on  the  two  wings,  owing  to  their  different  flying 
speeds  comes  into  account,  as  already  explained,  and  care  must  be 
taken  that  the  banking  does  not  increase  abnormally.  When  the 
turn  is  completed,  the  rudder  is  straightened  and  the  machine  is 
again  brought  to  an  even  keel  with  the  aid  of  the  wing-warping 
control,  or  the  ailerons.  The  effect  of  a  reverse  warping  to  prevent 
excessive  banking,  lowering  the  inside  wing  tip  incidentally,  puts  a 
slight  drag  on  that  wing  and  assists  in  the  action  of  turning,  as  does 
also  the  provision  of  small  vertical  planes  between  the  elevator  planes 
of  the  original  Wright  machine.  Since  the  adoption  of  the  headless 
type,  these  surfaces  are  placed  between  the  forward  ends  of  the  skids 
and  the  braces  leading  down  to  them. 

In  making  a  turn,  say,  to  the  left,  the  outside  or  right-hand 
wing  is  first  raised  by  lowering  the  wing  tip  on  that  side  and  the 
rudder  is  then  put  over  to  the  left.  When  the  correct  amount  of 
banking  is  acquired,  the  wing  tip  is  restored  to  its  normal  position, 
and  probably  the  left  wing  tip  may  have  to  be  lowered  slightly  to 
increase  the  lift  on  that  side  owing  to  its  reduced  speed.  When  the 
turn  is  completed,  the  rudder  is  straightened  out  and  the  left  wing 
tip  lowered  to  restore  the  machine  to  an  even  keel.  Both  Glenn 


BUILDING  AND  FLYING  AN  AEROPLANE         103 

Curtiss  in  this  country  and  R.  E.  Pelterie  in  France  have  shown 
that  it  is  possible  to  maneuver  without  using  the  rudder  at  all,  the 
ailerons  or  wing  tips  alone  being  relied  upon  for  this  purpose. 

Before  flights  in  other  than  calm  air  are  attempted,  much 
practice  is  required.  The  machine  must  be  inspected  over  and  over 
again,  and  the  wind  variations  studied  with  a  watchful  eye.  Not 
until  this  familiarity  with  machine  and  atmosphere  be  acquired 
should  flying  in  a  wind  be  attempted.  To  the  man  on  the 
ground,  wind  is  simply  air  moving  horizontally,  but  to  the  man 
in  the  air  it  is  quite  different.  Not  only  must  he  consider  horizontal 
movement,  but  vertical  draughts  and  vortices  as  well.  A  rising 
current  of  air  lifts  a  machine,  a  downward  current  depresses  it,  and 
he  must  learn  to  take  advantage  of  the  former  as  the  birds  do.  Hori- 
zontal currents  affect  forward  speed  over  the  ground;  swirls  and 
vortices  create  inequalities  in  wind  pressure  on  the  planes  and 
disturb  lateral  balance.  Familiarity  with  all  these  atmospheric 
conditions  can  be  acquired  only  after  long  practice.  Against  every 
tree,  house,  hill,  fence,  and  hedge  beats  an  invisible  surf  of  air; 
upward  currents  on  one  side  and  downward  on  the  other.  The  upward 
draught  is  not  usually  dangerous,  for  it  simply  lifts  the  machine;  but 
the  down  draught  will  cause  it  to  drop.  A  swift  downward  glide 
under  the  full  power  of  the  motor  must  then  be  made,  to  increase 
the  forward  speed  and  consequently  the  lift.  This  explains  why 
it  is  dangerous  to  fly  near  the  ground  in  a  wind;  likewise  why  the 
beginner  should  never  attempt  flying  at  first  in  anything  but  a  dead 
calm.  ( 

Turning  in  a  Wind.  When  turning  in  a  wind,  two  velocities 
must  be  borne  in  mind,  that  of  the  machine  relative  to  the  air  and 
that  relative  to  the  earth.  The  former  is  limited  at  its  lower  value 
to  that  of  the  flying  speed  of  the  machine,  and  the  latter  must  be 
considered  on  account  of  the  momentum  of  the  machine  as  a  whole. 
Change  of  momentum  is  a  matter  of  horse-power  and  weight  and 
is  the  governing  factor  in  flying  in  a  wind  on  a  circular  course.  Sup- 
pose the  flying  speed  of  a  machine  is  a  minimum  of  30  miles  an  hour 
relative  to  the  air,  and  a  wind  of  20  miles  an  hour  is  blowing.  The 
actual  speed  of  the  machine  relative  to  the  earth  in  flying  against 
the  wind  will  be  10  miles  an  hour.  If  it  be  desired  to  turn  down  the 
wind,  the  speed  of  the  machine  relative  to  the  earth  must  be  increased 


669 


104         BUILDING  AND  FLYING  AN  AEROPLANE 

from  10  miles  to  50  miles  an  hour  during  the  turn  and  a  correspond- 
ing change  of  momentum  must  be  overcome.  There  are  two  ways  of 
accomplishing  this,  either  by  speeding  up  the  motor  to  give  the 
maximum  power,  or  by  rising  just  previous  to  making  the  turn  and 
then  sweeping  down  as  the  turn  is  made,  thus  utilizing  the  accelera- 
tion due  to  gravity  to  assist  the  motor.  The  wind's  velocity  will 
assist  the  machine  also  and  during  the  turn  it  will  make  considerable 
leeway,  a  small  amount  of  which  is  deducted  to  counteract  the 
centrifugal  force  of  the  machine. 

Turning  in  a  contrary  direction,  i.  e.,  up  into  the  wind  when 
running  with  it,  requires  considerable  skill,  as  when  flying  50  miles 
an  hour,  the  tendency  on  rounding  a  corner  into  a  20-mile-an-hour 
wind  would  be  for  the  machine  to  rise  rapidly  in  the  air.  The  centrif- 
ugal force  at  such  a  speed  is  also  considerable,  causing  the  machine 
to  make  much  leeway  with  the  wind  during  the  turn.  Turning  under 
such  circumstances  should  be  commenced  early,  particularly  if 
there  are  any  obstructions  in  the  vicinity,  and  considerable  skill 
should  be  acquired  before  an  attempt  is  made  to  fly  in  such  a  wind. 

Starting  and  Landing.  A  machine  should  always  be  started 
and  landed  in  the  teeth  of  the  wind,  and  no  one  but  the  most  experi- 
enced aviators  can  afford  to  disregard  this  advice,  certainly  not  the 
novice.  The  precaution  is  necessary  because  in  landing  the  machine 
should  always  travel  straight  ahead  without  the  possibility  of  lurch- 
ing and  consequently  breaking  a  wing,  as  frequently  happens. 
Contact  with  the  ground  is  necessarily  made  at  a  time  when  the 
machine  is  traveling  over  it  at  a  speed  of  30  to  40  miles  per  hour 
and  skidding  sideways  at  10  to  15  miles  per  hour,  all  circumstances 
which  tend  to  wreck  an  aeroplane. 

Planning  a  Flight.  It  is  easy  to  lose  one's  way  in  the  air.  For 
that  reason  it  is  best  to  follow  the  Wright  idea  of  starting  out  with  a 
definite  plan,  and  of  landing  in  some  predetermined  spot,  as  aimless 
wandering  about  may  prove  disastrous  to  the  inexperienced  aviator. 
He  may  forget  which  way  the  wind  was  blowing,  or  how  much  fuel 
he  had,  or  the  character  of  the  ground  beneath  him.  Should  the 
motor  stop,  he  may  make  an  all  too  hasty  decision  in  landing.  It  is 
an  easy  matter  to  lose  one's  bearings  in  the  air,  not  only  because 
the  vehicle  is  completely  immersed  in  the  medium  in  which  it  is 
traveling,  but  also  because  the  earth  assumes  a  new  aspect  from  the 


670 


BUILDING  AND  FLYING  AN  AEROPLANE         105 

seat  of  an  aeroplane.  Cecil  Grace  was  one  of  those  who  lost  his 
bearings  and,  as  a  consequence,  his  life.  Ordinary  winds  blowing 
over  a  level  country  can  be  negotiated  with  comparative  safety. 
Not  so  the  puffy  wind.  To  cope  with  that,  constant  vigilance  is 
required,  particularly  in  turning.  In  a  circular  flight  in  a  steady 
wind,  the  only  apparent  effect  is  that  the  earth  is  swept  over  faster 
in  one  direction  than  in  the  other.  Before  a  cross-country  flight 
is  attempted,  the  starting  field  should  be  circled  over  at  a  great 
height,  as  not  until  then  may  the  long  distance  flight  be  started  in 
safety.  Cross-country  flying  is,  of  course,  fascinating,  and  it  is  a 
sore  temptation,  at  an  altitude  of  a  few  hundred  feet,  to  throw  off 
all  caution  and  fly  off  over  that  strange  country  below,  which  is, 
indeed,  a  new  land  as  viewed  from  aloft.  To  quote  a  professional 
aviator:  "Here  the  greatest  self-restraint  must  be  exercised.  Not 
until  the  necessary  practice  has  been  acquired,  not  until  the  right 
kind  of  confidence  has  been  gained,  may  one  of  these  trips  be 
attempted,  and  then  only  after  it  has  been  properly  planned." 

Training  the  Professional  Aviator.  Look  back  over  the  achieve- 
ments in  the  air  during  the  comparatively  short  time  that  man  has 
actually  been  flying,  and  it  will  be  noted  that  the  beginners,  burning 
up  with  the  enthusiasm  of  the  novice,  have  performed  the  most 
spectacular  feats  and  flown  with  the  greatest  fearlessness.  Curtiss 
was  comparatively  new  at  aviation  when  he  won  the  Gordon-Bennett 
at  Rheims  in  1909.  John  B.  Moisant,  the  sixth  time  he  ever  went 
up  in  an  aeroplane,  flew  from  Paris  to  London  with  a  187-pound 
passenger  and  302  founds  of  fuel,  oil,  and  spare  parts.  Hamilton 
made  his  successful  flight  from  New  York  to  Philadelphia  and 
return  when  he  was  hardly  more  than  a  novice,  while  Atwood's  great 
flights  from  St.  Louis  to  New  York  and  Boston  to  Washington  were 
made  before  his  name  had  become  known,  and  Beachey  had  been 
flying  only  a  few  months  when  he  broke  the  world's  altitude  record 
at  Chicago,  while  more  recent  achievements,  notably  Dixon's  flight 
across  the  Rockies,  have  emphasized  the  work  of  the  beginner.  All 
of  this  substantiates  the  belief  held  at  every  aviation  headquarters 
in  the  country — namely,  that  the  older  men  already  in  aviation 
may  improve  the  art  by  executive  ability  and  scientific  experiments, 
but  most  of  them  will  degenerate  as  flyers.  Beyond  a  certain  point, 
frequency  of  flight  does  not  necessarily  create  a  feeling  of  confidence 


671 


106         BUILDING  AND  FLYING  AN  AEROPLANE 

and  safety;  rather  it  brings  a  fuller  appreciation  of  the  dangers, 
and  the  men  who  best  know  how  to  fly  are  most  content  to  stay  upon 
the  ground. 

Professional  aviators  are  drawn  from  every  walk  of  life,  but 
trick  bicycle  performers,  acrobats,  parachute  jumpers,  and  racing 
automobile  drivers  make  the  most  promising  applicants.  By  a  kind 
of  sixth  sense,  both  the  Wrights  and  Curtiss  weed  out  the  promising 
ones  after  a  brief  examination.  They  select  men  who  have  an  almost 
intuitive  sense  of  balance.  Most  of  these,  provided  they  have  nerve, 
have  in  them  the  stuff  of  which  aviators  are  made,  even  though  they 
may  have  had  no  experience  in  any  line  akin  to  aviation.  Neither 
Curtiss  nor  the  Wrights  will  accept  women  under  any  condition. 
The  Moisant  school  does  not  share  this  discrimination  and  trained 
three  women  for  pilot's  licenses  during  1911. 

Curtiss  and  the  Weights  are  keen  in  their  realization  that 
recklessness  is  pulling  a  wing  feather  from  aviation  every  time  a 
man  is  killed,  and  they  are  doing  their  utmost  to  promote  conservatism. 
Curtiss  said  in  an  interview: 

I  do  not  encourage  and  never  have  encouraged  fancy  flying.  I  regard 
the  spectacular  gyrations  of  several  aviators  I  know  as  foolhardy  and  unneces- 
sary. I  do  not  believe  that  fancy  or  trick  flying  demonstrates  anything  except 
an  unlimited  amount  of  a  certain  kind  of  nerve  and  perhaps  the  possibilities 
of  what  is  valueless — aerial  acrobatics.  Some  aviators  develop  the  sense  of 
balance  very  rapidly,  while  others  acquire  it  only  after  long  practice.  It  may 
be  developed  to  a  large  extent  by  going  up  as  a  passenger  with  an  experienced 
man.  Therefore,  in  teaching  a  beginner,  I  make  it  a  point  to  have  him  make 
as  many  trips  as  possible  with  someone  else  operating  the  machine.  In  this 
way  the  pupil  gains  confidence,  becomes  accustomed  to  the  sensation  of  flying, 
and  is  soon  ready  for  a  flight  on  his  own  hook.  This  is  the  method  used.in  train- 
ing army  and  navy  officers  to  fly.  I  have  never  seen  novices  more  cautious 
and  yet  more  eager  to  fly  than  these  young  officers.  They  have  always  learned 
every  detail  of  their  machines  before  going  aloft,  and  largely  because  of  this 
they  have  developed  into  great  flyers.  Perhaps  it  is  due  to  the  military  bent 
of  their  minds;  at  any  rate,  they  have  made  good  almost  without  exception. 

ACCIDENTS  AND  THEIR  LESSONS 

Press  Reports.  Whenever  an  industry,  profession,  or  what 
not,  is  prominently  before  the  public,  every  event  connected  with 
it  is  regarded  as  "good  copy"  by  the  daily  press.  Happenings  of  so 
insignificant  a  nature  that  in  any  commonplace  calling  would  not 
be  considered  worthy  of  mention  at  all,  are  "played  up."  This  is 


672 


BUILDING  AND  FLYING  AN  AEROPLANE         107 

particularly  the  case  with  fatalities,  and  the  eagerness  to  cater  to  the 
morbid  streak  in  human  nature  has  been  responsible  for  the  unusual 
amount  of  attention  devoted  to  any  or  all  accidents  to  flying  machines, 
and  more  especially  where  they  have  a  fatal  ending.  In  fact,  this 
has  led  to  the  chronicling  of  many  deaths  in  the  field  of  aviation 
that  have  not  happened — some  of  them  where  there  was  not  even 
an  accident  of  any  kind.  For  instance,  in  many  of  the  casualty  lists 
published  abroad  from  time  to  time,  such  flyers  as  Hamilton,  Brook- 
ins,  and  others  have  figured  among  those  who  have  been  killed,  ever 
since  the  date  of  mishaps  that  they  had  months  ago. 

It  will  be  recalled  that  five  years  ago,  when  the  automobile 
began  to  assume  a  very  prominent  position,  every  fatality  for  which 
it  was  responsible  was  heralded  broadcast  where  deaths  caused  by 
other  vehicles  would  not  be  accorded  more  than  local  notice.  To  a 
large  extent,  this  is  still  true  and  will  probably  continue  to  be  the 
case  until  the  automobile  assumes  a  role  in  our  daily  existence  as 
commonplace  as  the  horse-drawn  wagon  and  trolley  car.  There  is 
undoubtedly  ample  justification  for  this  and  particularly  for  the 
editorial  comment  always  accompanying  it,  where  the  number  of 
lives  sacrificed  to  what  can  be  regarded  only  as  criminal  recklessness 
is  concerned.  Still,  the  fact  that  in  a  city  like  New  York  the  truck 
and  the  trolley  car  are  responsible  for  an  annual  death  roll  more 
than  twice  as  large  as  that  caused  by  the  automobile,  does  not  call 
for  any  particular  mention.  Horses  and  wagons,  we  have  always 
had  with  us,  and  the  trolley  car  long  since  became  too  commonplace 
an  institution  around  Which  to  build  a  sensation. 

As  the  most  novel  and  recent  of  man's  accomplishments,  the 
conquest  of  the  air  and  everything  pertaining  to  it  is  a  subject  on 
which  the  public  is  exceedingly  keen  for  news  and  nothing  appears 
to  be  of  too  trivial  import  to  merit  space.  Where  an  aviator  of  any 
prominence  is  injured,  or  succumbs  to  an  accident,  the  event  is 
accorded  an  amount  of  attention  little  short  of  that  given  the  death 
of  some  one  prominent  in  official  life.  During  the  four  years  that 
aviation  has  been  to  the  fore,  about  104  men  and  one  woman  have 
been  killed,  not  including  the  deaths  of  three  or  four  spectators 
resulting  from  accidents  to  aeroplanes,  during  this  period — i.  e.,  from 
the  beginning  of  1908  to  the  end  of  1911.  In  view  of  the  lack  of 
corroboration  in  some  cases,  the  figures  are  made  thus  indefinite. 


673 


108         BUILDING  AND  FLYING  AN  AEROPLANE 

Naturally  most  of  these  deaths  have  occurred  in  1910  and  1911— 
in  fact,  50  per  cent  took  place  from  1908  to  the  end  of  1910,  and  the 
remainder  during  1911,  since  these  years  were  responsible  for  a  far 
greater  development,  and  particularly  for  a  greater  increase  in  the 
number  engaged,  than  ever  before.  More  was  accomplished  in  these 
two  years  than  in  the  entire  period  intervening  between  that  day 
in  December,  1903,  when  the  Wright  Brothers  first  succeeded  in 
leaving  the  ground  in  a  power-driven  machine,  and  the  beginning 
of  1910. 

Fatal  Accidents.  Conceding  that  the  maximum  number  men- 
tioned, 105,  were  killed  during  the  four  years  in  question,  throughout 
the  world,  it  will  doubtless  come  as  a  surprise  to  many  to  learn 
that  this  is  probably  not  quite  twice  the  number  who  have  suc- 
cumbed to  football  accidents  during  the  same  time  in  the  United 
States  alone.  Authentic  statistics  place  the  number  thus  killed  at 
13  during  1908,  23  in  1909,  14  during  1910,  and  17  in  1911,  or  a  total 
of  67.  But  we  have  been  playing  football  for  a  couple  of  centuries 
or  more  and  this  is  regarded  as  a  matter  of  course.  The  death  of  a 
football  player  occurring  in  some  small,  out-of-the-way  place  would 
not  receive  more  than  local  attention,  unless  there  were  other  reasons 
for  giving  it  prominence,  so  that,  in  all  probability,  the  statistics  in 
question  fall  far  short  of  the  truth,  rather  than  otherwise. 

The  object  of  mentioning  this  phase  of  the  matter  is  to  place 
the  question  of  accidents  in  its  true  light.  That  the  development 
of  any  new  art  is  bound  to  be  attended  by  numerous  mishaps,  many 
of  them  fatal,  goes  without  saying  and  it  is  something  that  can  not 
be  ignored.  Nothing  could  be  worse  than  attempting  to  gloss  over 
or  belittle  the  loss  of  life  for  which  aviation  has  been  responsible 
and  doubtless  will  continue  to  be.  Progress  invariably  takes  its 
toll  and  it  is  more  often  founded  upon  failure  than  unvarying  success, 
for  every  accident  is  a  failure,  in  a  sense,  and  every  accident  carries 
with  it  its  own  lesson. 

Where  the  cause  is  apparent,  it  gives  an  indication  of  the  remedy 
which  will  bring  about  the  prevention  of  its  recurrence.  In  other 
words,  it  serves  to  point  out  weaknesses  and  shows  what  is  necessary 
to  overcome  them.  For  that  reason  alone  is  the  question  of  accidents 
taken  up  here,  as  a  study  of  those  that  have  occurred  points  the  way 
to  improvement.  Table  III  gives  a  resume  of  the  more  impor- 


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675 


110         BUILDING  AND  FLYING  AN  AEROPLANE 

tant  fatalities  that  have  resulted  from  the  use  of  a  heavier-than-air 
machine  during  the  past  four  years: 

Fatalities  greatly  increased  in  number  during  1911,  but  not  out 
of  proportion  to  the  greatly  augmented  number  of  aviators.  With 
comparatively  few  exceptions,  however,  the  accidents  were  more  or 
less  similar  in  their  nature  to  those  already  tabulated,  so  that  it 
would  be  of  no  particular  value  to  extend  the  comparison  in  this 
manner  to  cover  them.  Many  of  the  fatalities  during  that  year  were 
not  of  the  aviators  themselves,  but  of  the  spectators,  a  fact  which  calls 
attention  to  a  danger  that  has  not  been  fully  appreciated  before. 
At  the  start  of  the  Paris-Madrid  race,  the  French  minister  of  war 
and  another  official  were  killed  by  a  monoplane  plunging  into  the 
crowd,  and  on  the  same  day,  May  21,  1911,  five  people  were  killed 
at  Odessa,  Russia,  in  the  same  manner.  An  unusual  type  of  mishap, 
not  mentioned  in  the  tabulation  and  in  which  three  or  four  aviators 
lost  their  lives  during  1911,  was  the  burning  of  the  aeroplane  in 
midair,  or  the  explosion  of  the  gasoline,  setting  fire  to  the  wings 
and  either  burning  the  aviator  at  his  post  or  killing  him  by  the  fall. 
One  such  accident  occurred  in  France  in  September,  another  in 
Spain  two  days  later,  and  a  third  in  Germany,  in  which  two  men 
were  killed.  Accidents  of  an  even  more  unusual  nature  were  the 
collision  of  two  biplanes  in  midai'r  at  St.  Petersburg,  the  collision  of 
a  motorcycle  with  a  biplane  as  it  swooped  down  on  a  race  track,  and 
the  partial  wrecking  of  Fowler's  biplane  by  a  bull  upon  landing 
near  Fort  Worth,  Texas,  but  these,  of  course,  had  no  bearing  on  the 
design  of  the  machines. 

Apart  from  those  specially  referred  to,  the  great  majority  of 
accidents  during  1911  may  be  ascribed  to  two  or  three  of  the  causes 
detailed  in  connection  with  the  comparative  table.  Of  these,  lack  of 
experience  and  foolhardiness  stand  out  prominently,  the  latter  un- 
doubtedly causing  the  double  fatality  at  Chicago  when  two  aero- 
planes plunged  into  Lake  Michigan,  drowning  one  of  the  aviators, 
while  a  third  machine  collapsed  in  mid-air,  hurling  the  aviator  to 
his  death  on  the  field.  Careful  reading  of  the  reports  of  a  large 
number  of  these  accidents  usually  brings  to  light  the  statement  "in 
attempting  to  make  a  quick  turn,"  or  similar  phrase,  showing  that 
the  moving  cause  of  the  accident  was  due  to  subjecting  the  parts  of 
the  machine  to  excessive  stresses,  as  outlined  in  the  following  pages. 


676 


BUILDING  AND  FLYING  AN  AEROPLANE         111 

Causes.  Lack  of  Experience.  It  will  be  at  once  noticeable 
by  Table  III  that  out  of  a  total  of  28,  no  less  than  16,  or  considerably 
more  than  half  of  the  accidents,  were  due  in  one  way  or  another  to 
lack  of  experience.  In  other  words,  the  aviators  had  not  fully  com- 
plied with  the  cardinal  principle  for  success  in  flying  upon  which 
the  Wright  Brothers  have  always  laid  so  much  stress,  i.  e.,  you  must 
first  learn  to  fly  before  you  can  attempt  to  go  aloft  safely.  Nothing 
short  of  a  thorough  mastery  of  the  machine  can  suffice  to  give  the 
aviator  the  ability  to  do  the  right  thing  at  the  right  moment,  in  the 
great  majority  of  cases.  There  will  always  be  occasions  when  even 
the  most  skilled  aviator  will  make  errors  of  judgment  and  frequently 
they  cost  him  his  life.  But  this  is  equally  true  of  every  dangerous 
calling,  whether  it  be  running  an  automobile,  driving  a  locomotive, 
or  doing  any  of  the  thousand  and  one  things  where  the  responsibility 
for  his  own  and  other  lives  is  placed  in  one  man's  hands  and  depends 
to  a  large  extent  on  his  discretion  and  judgment  in  cases  of  emergency, 
so  that  there  will  be  fatalities  from  this  cause  as  long  as  man  con- 
tinues to  fly.  This  involves  the  personal  equation  that  must  always 
be  reckoned  with.  Just  how  many  of  the  accidents  that  have  resulted 
in  the  fatalities  set  forth,  have  been  due  to  the  fallibility  of  the  operator 
and  for  how  much  the  design  of  the  current  types  of  machines  is 
responsible,  would  be  hard  to  say.  Fig.  45,  for  example,  which  shows 
H.  V.  Roe  in  the  act  of  striking  the  ground  in  his  triplane,  illustrates 
an  accident  due  to  bad  design.  Methods  of  control  will  be  improved 
and  simplified  and  made  as  nearly  "fool-proof"  as  human  ingenuity 
can  accomplish,  but  experience  in  other  fields  has  demonstrated 
unmistakably  that  they  can  never  be  developed  to  a  point  where  it 
is  impossible  to  do  the  wrong  thing.  With  skill  at  such  a  premium 
in  callings  of  responsibility  which  involve  only  conditions  that  have 
been  familiar  for  years,  how  much  more  so  must  it  be  in  the  air 
about  which  so  little  is  known?  Consequently,  the  real  danger  is  to 
be  found  in  the  personal  equation,  just  as  it  is  in  every  other  mode 
of  conveyance,  despite  the  fact  that  it  has  been  perfected  to  a  point 
which  apparently  admits  of  little  further  development  where  safe- 
guarding it  is  concerned. 

Obstructions.  Obstructions  are  bound  to  play  a  prominent 
part  in  accidents  to  any  method  of  conveyance,  but  less  so  in  aviation 
than  in  any  other,  as  it  is  only  in  rising  and  alighting  that  this  danger 


677 


112        BUILDING  AND  FLYING  AN  AEROPLANE 


678 


BUILDING  AND  FLYING  AN  AEROPLANE         113 


679 


114         BUILDING  AND  FLYING  AN  AEROPLANE 

is  present.  Of  the  two  fatal  accidents  ascribed  to  this  cause,  one 
resulted  from  colliding  with  an  obstruction  while  running  along  the 
ground  preparatory  to  rising,  and  the  other  from  striking  an  obstruc- 
tion in  flight,  Fig.  46.  In  view  of  the  numerous  cross-country  flights 
that  have  been  made,  trips  across  cities  and  the  like,  it  is  to  be  mar- 
veled at  that  up  to  the  present  writing  no  fatalities  have  been  caused 
by  what  the  aviator  most  dreads  when  leaving  the  safety  of  the  open 
field,  that  is,  being  compelled  to  make  a  landing  through  stoppage 
of  the  motor,  whether  from  a  defection  or  lack  of  fuel.  While  no 
fatalities  have  as  yet  to  be  put  down  to  this  ever-present  danger 
in  extended  flights,  an  accident  that  might  have  had  a  fatal  termina- 
tion, occurred  to  Le  Blanc  during  the  competition  for  the  Gordon- 


Fig.  47.     Overturned  Monoplane  Due  to  a  Start  in  a  Gale 

Bennett  trophy,  which  was  the  chief  event  of  the  International  Meet 
in  October,  1910,  at  Belmont  Park,  near  New  York.  Le  Blanc  and 
his  fellow  compatriots  who  were  eligible  were  all  experienced  cross- 
country flyers,  the  former  having  won  the  Circuit  de  L'Est,  a  race 
around  France,  and  by  far  the  most  ambitious  of  its  kind  which  had 
been  attempted  up  to  that  time.  They  accordingly  protested  most 
vigorously  against  flying  over  the  American  course  to  compete  for 
the  cup  which  Curtiss  had  captured  at  Rheims  the  year  before, 
owing  to  the  fact  that  it  presented  numerous  dangerous  obstructions 
in  the  form  of  trees  and  telegraph  poles.  But  as  it  was  impossible 
to  provide  any  other  convenient  five-kilometer  circuit  (3.11  miles) 
as  called  for  by  the  conditions,  the  protest  was  of  no  avail.  After 


680 


BUILDING  AND  FLYING  AN  AEROPLANE        115 

having  covered  19  of  the  20  laps  necessary  to  complete  the  distance 
of  100  kilometers  in  time  that  had  never  been  approached  before, 
Le  Blanc  was  compelled  to  descend  through  lack  of  fuel,  and  as  he  had 
not  risen  more  than  80  to  100  feet  at  any  time  during  the  race,  this 
meant  coming  down  the  moment  the  motor  stopped.  The  result  was  a 
collision  with  a  telegraph  pole,  breaking  it  off  and  wrecking  the  mono- 
plane, the  aviator  fortunately  escaping  any  serious  injury.  During 
the  same  meet  Moisant  demolished  his  Bleriot  monoplane  by  trying 
to  start  in  the  face  of  a  high  wind,  Figs.  47  and  48: 

Stopping  of  Motor.     The  mere  fact  that  the  motor  stops  does 
not  necessarily  mean  a  disastrous  ending  to  a  flight,  as  is  very  com- 


Fig.   48.     View  of  Moisant  Monoplane  after  a  Bad  Spill 

monly  believed,  this  having  been  strikingly  illustrated  by  Brookins' 
glide  to  earth  from  an  altitude  of  5,000  feet  with  the  motor  dead, 
and  Moisant's  glide  from  an  even  greater  height  in  France.  But  it 
does  mean  a  wreck  unless  a  suitable  landing  place  can  be  reached 
with  the  limited  ability  to  control  the  machine  that  the  aviator  has 
when  he  can  no  longer  command  its  power.  Motors  will  undoubtedly 
become  more  and  more  reliable  as  development  progresses,  but  the 
human  equation — the  partly-filled  fuel  tank,  the  loose  adjustment 
that  is  overlooked  before  starting,  and  a  hundred  and  one  things  of 
a  similar  nature — will  always  play  their  role,  so  that  compulsory 
landing  in  unsuitable  places  will  always  constitute  a  source  of  danger 
as  flights  become  more  and  more  extended. 


681 


116         BUILDING  AND  FLYING  AN  AEROPLANE 

Breakage  of  Parts  of  Aeroplanes.  In  studying  the  foregoing 
table,  it  can  only  be  a  source  of  satisfaction  to  the  intelligent  student 
and  believer  in  aerial  navigation,  to  note  how  large  a  proportion 
of  the  accidents  is  due  to  the  breakage  of  parts  of  the  machine. 
This  implies  a  fault  in  construction,  but  not  in  principle.  It  reveals 
the  fact  that,  in  the  attempt  to  secure  lightness,  strength  has  some- 
times been  sacrificed,  chiefly  through  lack  of  appreciation  of  the 
stresses  to  which  the  machine  is  subjected  in  operation.  At  a  time 
when  weight  is  regarded  almost  as  the  paramount  factor  by  so  many 
builders,  it  is  inevitable  that  some  should  err  by  shaving  things  too 
fine.  Lightness  is  an  absolute  necessity  and  failure  to  achieve  it  in 
every  instance  without  eliminating  the  factor  of  safety  has  been  due 
more  to  the  crude  methods  of  construction  and  lack  of  suitable  mate- 
rials, than  any  other  cause — conditions  that  are  bound  to  obtain  in  the 
early  days  of  any  art.  Construction  is  improving  rapidly,  but 
progress  is  bound  to  be  attended  with  accidents  of  this  nature.  The 
fact  that  their  proportion  is  greatly  diminishing  despite  the  rapidly 
increasing  number  of  aviators  is  the  best  evidence  of  what  is  being 
accomplished.  When  machines  are  built  with  such  a  high  factor 
of  safety  in  every  part  that  breakage  is  an  almost  unheard-of  thing, 
failures  from  this  cause  will  have  been  reduced  to  an  unsurpassable 
minimum. 

Failure  of  the  Control  Mechanism.  Under  the  general  classifica- 
tion B,  are  included  not  alone  those  accidents  directly  due  to  break- 
age of  some  vital  part,  but  also  those  instances  in  which  some  element 
of  the  control,  such  as  the  elevator,  has  become  inoperative  through 
jamming.  When  an  accident  happens  in  the  air,  it  takes  place  SQ 
quickly  and  the  machine  is  so  totally  wrecked  by  falling  to  the  ground, 
that  it  is  usually  difficult  to  determine  the  exact  nature  of  the  cause 
through  a  subsequent  examination  of  the  parts,  so  that  it  can  seldom 
be  stated  with  certainty  just  what  the  initial  defection  consisted  of, 
though  it  may  be  regarded  as  a  foregone  conclusion  that,  in  the  case 
of  experienced  aviators  who  have  previously  demonstrated  their 
ability  to  cope  with  all  ordinary  emergencies,  nothing  short  of  the 
failure  of  some  vital  part  could  have  caused  their  fall. 

This  was  the  case  with  Johnstone's  accident  at  Denver — an 
occurrence  illustrating  another  phase  of  the  personal  equation  that 
must  be  taken  into  consideration  when  noting  the  lessons  to  be 


682 


BUILDING  AND  FLYING  AN  AEROPLANE         117 

learned  from  a  study  of  accidents  and  their  causes.  It  is  simply 
the  old,  old  story  of  familiarity  breeding  contempt  —  the  miner 
thawing  out  sticks  of  dynamite  before  an  open  fire.  Due  to  the 
rarefied  air  of  Denver,  which  is  at  an  elevation  of  more  than  5,000 
feet,  Johnstone  had  underestimated  the  braking  powers  of  the  air 
on  the  machine  in  landing  the  day  previous  and  had  crashed  into  a 
fence,  breaking  one  of  the  right  outermost  struts  between  the  sup- 
porting planes. 

Proper  regard  for  safety  should  naturally  have  called  for  its 
replacement  by  an  entirely  new  strut,  but  conditions  at  flying  meets 
as  at  present  conducted  make  quick  repairs  to  damaged  machines 
imperative.  The  damaged  upright  was  accordingly  glued  and  braced 
by  placing  iron  rings  around  it,  the  rings  themselves  being  held  in 
place  by  ordinary  nails  passing  through  holes  in  the  iron  large  enough 
to  let  the  nail  head  slip  through.  The  vibration  of  the  motor  and 
the  straining  of  the  strut  in  warping  the  wings  caused  the  nails  to 
work  out  of  the  holes,  permitting  the  rings  to  slide  out  of  place  as 
well.  Johnstone  was  an  accomplished  aviator,  much  given  to  the 
execution  of  aerial  maneuvers  only  possible  to  the  skilled  flyer  of 
quick  and  ready  judgment.  But  such  performances  impose  excessive 
stresses  on  the  supporting  planes  and  their  braces,  and  one  of  John- 
stone's  quick  turns  caused  the  repaired  struts  to  collapse  through 
the  strain  of  sharply  warping  the  wing  tips  on  that  side.  He  imme- 
diately attempted  to  restore  the  balance  of  the  machine  by  bringing 
the  left  wing  down  with  the  control,  then  tried  to  force  the  twisting 
on  the  right  side,  sulp seeding  momentarily,  and  a  few  seconds  later 
losing  all  control  and  crashing  to  the  ground.  It  appeared  to  demon- 
strate that  even  wrhen  disabled  an  aeroplane  is  not  entirely  without 
support,  but  has  more  or  less  buoyancy — something  which  is  really 
more  of  an  optical  illusion  than  anything  else  due  to  underestimating 
the  speed  at  which  a  body  falls  from  any  great  height.  Johnstone 's 
accident  was  the  first  of  its  kind,  in  that  he  fell  from  a  height  of  about 
800  feet,  during  the  first  500  of  which  he  struggled  to  regain  control 
of  the  machine,  finally  dropping  the  remaining  300  feet  apparently 
as  so  much  dead  weight.  It  showed  in  a  most  striking  manner  the 
vital  importance  of  the  struts  connecting  the  supporting  surfaces  of 
the  biplane,  any  damage  to  them  resulting  in  the  crippling  of  the 
balancing  devices  and  the  end  of  all  aerial  support. 


683 


118         BUILDING  AND  FLYING  AN  AEROPLANE 

Biplane  vs.  Monoplane.  It  requires  only  a  glance  at  Table  III 
to  show  that  the  greater  number  of  accidents  have  happened  to 
the  biplane,  yet  the  latter  is  generally  regarded  as  the  safer  of  the 
two.  Prior  to  Delagrange's  fatal  fall  in  January,  1910,  there  had 
been  only  four  fatalities  with  modern  flying  machines:  Self  ridge 
and  Lefebre  were  killed  in  Wright  machines,  the  latter  of  French 
manufacture,  Ferber  lost  control  of  his  Voisin  biplane,  and  Fer- 
nandez was  killed  flying  a  biplane  of  his  own  design.  In  one  case  at 
least,  that  of  Lieutenant  Selfridge,  the  accident  appears  to  have 
been  due  to  the  failure  of  a  vital  part — the  propeller.  It  has  since 
become  customary  to  cover  the  tips  of  propellers  for  at  least  a  foot 
or  so  with  fabric  tightly  fitted  and  varnished  so  as  to  become  prac- 
tically an  integral  part  of  the  wood.  This  prevents  splintering  as 
well  as  avoiding  the  danger  of  the  laminations  succumbing  to  cen- 
trifugal force  and  flying  apart.  At  the  extremely  high  speeds,  par- 
ticularly at  which  direct-driven  propellers  are  run,  the  stress  imposed 
on  the  outer  portion  of  the  blades  by  this  force  is  tremendous.  In 
making  any  attempt  to  compare  the  number  of  accidents  to  the 
biplane  and  the  monoplane,  it  must  also  be  borne  in  mind  that  the 
former  has  been  in  the  majority. 

Delagrange's  accident  offers  two  special  features  of  technical 
interest.  It  was  the  first  fatality  to  happen  with  the  monoplane 
and  was  likewise  the  first  fatal  accident  which  appeared  to  be  dis- 
tinctly due  to  a  failure  of  the  main  structure  of  the  machine.  For 
obvious  reasons,  it  is  usually  difficult  to  definitely  fix  the  cause  of 
an  accident,  but  in  this  case  there  seemed  good  reason  to  suppose 
that  the  main  framing  of  one  of  the  wings  gave  way  altogether. 
Curiously  enough,  Santos-Dumont  had  an  accident  the  day  following 
from  an  exactly  similar  cause,  the  machine  plunging  to  the  ground. 
But  with  the  good  fortune  that  has  attended  this  experimenter 
throughout  his  long  aerial  career,  he  was  uninjured.  It  was  definitely 
established  that  the  cause  was  the  fracture  of  one  of  the  wires  taking 
the  upward  thrust  of  the  wing.  In  the  case  of  the  biplane,  the  top 
and  bottom  members  are  both  of  wood,  with  wooden  struts,  the 
whole  being  braced  with  numerous  ties  of  wire.  In  the  monoplane, 
however,  the  main  spars  are  trussed  to  a  strut  below  by  a  compara- 
tively small  number  of  wires.  The  structure  of  each  wing  is,  in  fact, 
very  much  like  the  rigging  of  a  sailboat,  the  main  spars  taking  the 


684 


BUILDING  AND  FLYING  AN  AEROPLANE         119 

place  of  the  mast  while  the  wire  stays  take  that  of  the  shrouds,  with 
this  very  important  difference,  that  the  mast  of  the  boat  is  provided 
with  a  forestay  to  take  the  longitudinal  pressure  when  going  head 
to  the  wind,  while  the  wing  of  an  aeroplane  often  has  no  such  pro- 
vision, the  longitudinal  pressure  due  to  air  resistance  being  taken 
entirely  by  the  spar. 

It  is  quite  possible  that  this  had  something  to  do  with  Dela- 
grange's  accident,  as,  in  the  effort  to  make  a  new  record,  his  Bleriot 
had  just  been  fitted  with  a  very  much  more  powerful  motor.  In  fact, 
double  that  for  which  the  machine  was  originally  designed,  and  this 
was  given  by  the  maker  as  the  probable  cause  of  the  mishap.  As  the 
new  motor  wras  of  a  very  light  type,  the  extra  weight,  if  any,  was 
quite  a  negligible  proportion  of  the  total  weight  of  the  machine. 
The  vertical  stresses  on  the  wings  and  their  supporting  wires  would, 
therefore,  not  be  materially  increased.  But  as  the  more  powerful 
engine  drove  the  wings  through  the  air  a  great  deal  faster,  the  stresses 
brought  upon  them  by  the  increased  resistance  would  be  substan- 
tially augmented  and,  unless  provision  were  made  for  this,  the  factor 
of  safety  would  be  much  reduced.  Whether  the  failure  of  the  wing 
was  actually  from  longitudinal  stress  or  the  breaking  'of  a  support- 
ing wire,  as  in  Santos-Dumont's  case,  will  never  be  known,  but  it  is 
quite  clear  that  the  question  of  ample  strength  to  resist  longitudinal 
stresses  should  be  carefully  considered,  especially  when  increasing 
the  power  of  an  existing  machine. 

The  question  of  the  most  suitable  materials  and  fastenings 
for  the  supporting  wires  is,  moreover,  a  matter  which  requires  very 
careful  consideration.  In  the  case  of  the  biplane,  the  wires  are  so 
numerous  that  the  failure  of  one,  or  even  more,  may  not  endanger 
the  whole  structure,  but  those  of  the  monoplane  are  so  few  that  the 
breaking  of  but  one  may  mean  the  loss  of  the  wing.  In  this  respect, 
as  in  others,  the  conditions  are  parallel  to  the  mast  of  the  sailboat. 
It  is  only  reasonable  to  expect,  therefore,  that  similar  materials 
would  be  best  adapted  to  the  purpose.  At  present,  however,  the 
stays  of  aeroplane  wings  are  almost  invariably  solid  steel  wire,  or 
ribbon,  while  marine  shrouds  are  always  of  stranded  wire  rope,  solid 
wire  not  having  been  found  satisfactory.  Weight  for  weight,  the 
solid  wire  will  stand  a  greater  strain  when  tried  in  a  testing  machine 
than  will  the  stranded  rope,  but  practice  has  always  demonstrated 


685 


120         BUILDING  AND  FLYING  AN  AEROPLANE 

that  it  is  not  so  reliable.  The  stranded  rope  never  breaks  without 
warning,  and  sometimes  several  of  its  wires  may  go  before  the  whole 
gives  way.  As  the  breakage  of  the  strands  can  be  easily  seen,  it  is 
possible  to  replace  a  damaged  stay  before  it  becomes  unsafe.  In  the 
case  of  a  single  wire,  there  is  nothing  to  show  whether  it  has  dete- 
riorated or  not.  It  seems  a  doubtful  policy  to  use  in  an  aeroplane 
what  experience  has  shown  not  to  be  good  enough  for  a  boat,  and 
stranded  wire  cables  particularly  designed  for  aeronautic  use  are 
now  being  placed  on  the  market  in  this  country. 

Record  Breaking.  Striving  after  records  has  undoubtedly 
proved  one  of  the  most  prolific  causes  of  accident.  What  is  wanted 
to  make  the  aeroplane  of  the  greatest  practical  use  is  that  it  should 
be  safe  and  reliable.  The  tendency  of  record-breaking  machines  is 
the  exact  opposite  of  this,  as  the  weights  of  all  the  most  essential 
parts  must  be  cut  down  to  the  finest  limits  possible  in  order  to 
provide  sufficient  power  and  fuel-carrying  capacity  for  the  record 
flight.  It  is,  in  fact,  generally  the  case  in  engineering  that  the  design 
and  •  materials  which  will  give  the  best  results  for  a  short  time  are 
essentially  different  from  those  which  are  the  most  reliable,  and 
striving  after  speed  records  consists  simply  in  disregarding  safety 
and  reliability  to  the  greatest  extent  to  which  the  pilots  are  willing 
to  risk  their  necks,  and  there  is  no  difficulty  in  getting  men  to  take 
practically  any  risk  for  the  substantial  rewards  offered. 

The  performance  of  specially  sensational  feats  in  the  air  is  like- 
wise a  fertile  source  of  accidents.  One  noted  aviator  who  has  the 
reputation  of  being  a  most  conservative  and  expert  operator,  while 
endeavoring  to  land  within  a  set  space,  made  too  sudden  a  turn,  which 
resulted  in  the  tail  of  the  machine  giving  way,  precipitating  him  to 
the  ground.  In  fact,  the  number  of  failures  resulting  from  abrupt 
turns  shows  conclusively  that  there  is  too  small  a  factor  of  safety  in 
the  construction,  not  because  the  added  weight  could  not  be  carried, 
but  because  the  extreme  lightness  alone  made  possible  the  stunts 
for  which  there  is  always  applause  or  financial  reward.  It  may  seem 
strange  to  the  man  whose  only  interest  in  aeronautics  is  that  of  an 
observer,  that  so  many  should  be  willing  to  take  such  unheard-of 
chances;  that  an  aeronaut  will  rise  to  great  heights,  knowing  in 
advance  that  a  vital  part  of  his  machine  has  been  deranged,  or  is 
only  temporarily  repaired;  and  that  many  others  will  attempt  ambi- 


686 


BUILDING  AND  FLYING  AN  AEROPLANE         121 

tious  flights  with  engines  or  other  parts  that  have  never  been  tested 
previously  in  operation  in  the  air.  Many  young  and  inexperienced 
aviators  are  not  content  to  thoroughly  test  out  each  new  part  on  the 
ground,  or  close  to  it,  but  must  go  aloft  at  once  to  do  their  experi- 
menting, with  the  usual  result  of  such  foolhardiness.  If  in  other 
sports  safe  conditions  were  absolutely  disregarded  in  this  manner 
—take  football  as  an  instance — the  resulting  fatalities  would  not  be 
charged  against  the  sport  itself.  But  aviation  is  so  extremely 
novel  and  likewise  so  mysterious  to  the  uninitiated  that  this  is  never 
taken  into  consideration. 

Excessive  Lightness  of  Machines.  If,  even  at  the  present  early 
stage  of  aviation,  machines  are  being  made  excessively  light  for 
purposes  of  competition,  it  is  time  that  the  contest  committees  of 
organizations  in  charge  of  meetings  formulate  rules  as  to  the  size  of 
engines,  weight  of  machines,  and  similar  factors,  so  that  accidents 
will  not  only  be  reduced  to  a  minimum,  but  competition  along  proper 
lines  will  develop  types  of  machines  which  are  useful  and  not  merely 
racing  freaks,  as  has  already  been  done  in  the  automobile  field. 
Hair-raising  performances  also  should  be  prohibited,  at  least  until 
such  time  as  improvements  in  the  construction  of  machines  make 
it  reasonably  certain  that  they  are  able  to  withstand  the  terrific 
strains  imposed  upon  them  in  this  manner.  Suddenly  attempting 
to  bring  the  machine  to  a  horizontal  plane  after  a  long  dip  at  an 
appalling  angle  is  an  extremely  dangerous  maneuver,  whether  it  be 
taken  in  the  upper  air  or  is  one  of  the  now  familiar  long  glides  to 
earth,  which  require  pulling  up  short  when  within  a  few  feet  of  the 
ground  and  after  the  dropping  machine  has  acquired  considerable 
inertia.  The  aviator  is  simply  staking  his  life  against  the  ability  of 
the  struts  and  stays  to  withstand  the  terrific  stresses  imposed  upon 
them  every  time  this  is  done.* 

As  at  present  constructed,  many  of  the  machines  are  not  suf- 
ficiently strong  to  withstand  the  utmost  in  the  way  of  speed  and 
sudden  turns  which  the  skilled  operator  is  likely  to  put  on  them. 
They  should  be  made  heavier,  or  of  materials  providing  greatly 
increased  strength  with  the  same  weight.  That  they  can  be  made 
heavier  without  seriously  damaging  their  flying  ability  has  been 


*This  is  exactly  what  occurred  at  the  Chicago  Meet,  August  15,  1911,  when  Badger's 
Baldwin  biplane  collapsed  at  the  end  of  a  long  dive,  causing  the  death  of  the  aviator. 


687 


122 


BUILDING  AND  FLYING  AN  AEROPLANE 


clearly  demonstrated  by  the  numerous  flights  with  one  and  two 
passengers,  and  on  one  occasion  in  which  three  passengers  besides 
the  driver  were  taken  up  on  an  ordinary  machine.  This  was  likewise 
tempting  fate  by  overloading,  but  it  served  to  show  the  possibilities. 
Landings.  Then  there  is  a  class  of  accidents  for  which  neither 
the  aviator  nor  the  machine  is  responsible,  as  where  spectators  have 
crowded  on  the  field,  causing  the  flyers  to  make  altogether  too  sudden 


Fig.  49.     Monoplane  is  Liable  to  Stand  on  its  Head  if  Landing  is  Not  Properly  Made 

or  impromptu  landings  at  angles  which  would  otherwise  not  be  con- 
sidered for  a  moment.  This,  of  course,  refers  solely  to  exhibition  meets, 
and  the  comparative  immunity  of  cross-country  flights  from  fatal 
accidents  as  compared  with  the  latter,  speaks  for  itself  in  this  respect. 
In  the  open,  even  the  novice  seems  to  be  able  to  pick  a  safe  landing, 
especially  if  high  enough  to  glide  some  distance  before  reaching  the 
ground.  This  brings  out  the  fact  that,  as  a  rule,  the  machines  are 


688 


BUILDING  AND  FLYING  AN  AEROPLANE         123 

safer  in  the  air — a  large  part  of  the  danger  lies  in  making  a  landing. 
Starting  places  are  usually  smooth,  but  landing  places  may  be  the 
reverse.  When  alighting  directly  against  the  wind,  which  is  the  only 
safe  practice,  most  of  the  machines  will  remain  on  an  even  keel  until 
they  come  to  a  stop,  but  the  slightest  bump  or  depression,  in  connec- 
tion with  a  side  gust  of  wind,  may  swerve  it  around  and  capsize  it,  as 
demonstrated  by  the  illustration  of  a  bad  landing  by  De  Lesseps, 
Fig.  49.  This  was  emphasized  by  some  of  the  minor  accidents  at  the 
International  Meet  near  New  York.  There  is  no  precision  or  accuracy 
in  the  movements  of  a  flying  machine  when  rolling  slowly  over  the 
ground  after  the  engine  has  been  shut  off,  and  the  aviator  is,  to  a  cer- 
tain extent,  helpless.  The  wheels  on  most  machines  are  placed  too 
near  the  center  and  too  close  together/  When  an  attempt  is  made 
to  land  with  the  wind  on  the  quarter  or  side,  although  the  machine 
may  strike  the  ground  safely,  owing  to  the  accuracy  with  which  it 
may  be  controlled  in  the  air  while  at  speed,  it  is  apt  to  turn  after 
rolling  a  short  distance  and  the  wind  will  then  easily  capsize  it,  break- 
ing a  wing,  smashing  a  propeller,  and  sometimes  injuring  the  motor 
or  the  aviator.  Accidents  from  this  cause  have  been  common. 

These  accidents  and  collisions  with  obstructions  make  plain  the 
fact  that  brakes  are  quite  as  necessary  on  an  aeroplane  as  on  any 
other  vehicle  intended  to  run  on  the  ground.  Practically  all  aero- 
planes are  fitted  with  pneumatic  tires  and  ball-bearing  wheels  and, 
as  there  is  very  little  head  resistance,  they  will  run  a  considerable 
distance  after  alighting  at  a  speed  of  20  to  30  miles  an  hour.  The 
employment  of  a  brake  on  the  wheels  would  have  averted  one  of 
the  fatal  accidents  abroad,  as  noted  in  Table  III.  They  would 
have  enabled  Johnstone  to  stop  his  machine  before  colliding  with 
the  fence  surrounding  the  aviation  grounds  at  Denver,  and  they 
would  have  prevented  several  minor  accidents  at  various  meets, 
which,  though  not  endangering  the  aviator  in  every  instance,  have 
often  seriously  damaged  his  machine.  Every,  exhibition  field  is 
obstructed  by  fences,  posts,  buildings,  and  the  like,  and  to  avoid  com- 
ing in  contact  with  these,  as  well  as  with  the  irrepressible  spectator, 
the  aviator  should  certainly  have  an  effective  means  of  bringing  the 
machine  to  a  standstill  when  it  is  running  along  the  ground.  How 
much  more  so  is  this  necessary  for  cross-country  flying  when  the  choice 
of  a  landing  place  is  a  difficult  matter  at  best.  Ability  to  come  to  a 


689 


124         BUILDING  AND  FLYING  AN  AEROPLANE 

stop  quickly  would  make  it  possible  to  land  in  restricted  places  where 
only  a  very  limited  run  along  the  ground  could  be  had. 

Lack  of  Sufficient  Motor  Control.  Another  class  of  accidents 
that  take  place  on  the  ground  suggests  the  necessity  for  improving 
the  motor  control.  In  alighting,  the  motor  is  usually  stopped  by 
cutting  off  the  ignition — ordinarily  by  grounding  or  short-circuiting. 
Throttling  to  stop  appears  to  be  seldom  resorted  to,  but  as  several 
instances  have  occurred  in  which  the  aviator  found  it  impossible  to 
cut  off  the  ignition,  resulting  in  a  collision  with  another  machine  or 
a  building,  it  is  evident  that  the  control  should  be  arranged  so  that 
both  methods  could  be  employed.  With  the  increasing  use  of  air- 
cooled  motors  that  may  continue  to  run  through  self-ignition  after 
the  spark  has  been  cut  off,  this  is  more  necessary  than  ever. 

While  it  has  been  demonstrated  that  the  stoppage  of  the  motor 
does  not  necessarily  involve  a  fall,  most  aviators  will  naturally  prefer 
to  command  the  assistance  of  the  motor  at  all  times,  and  in  the  case 
of  motors  using  a  carbureter  this  should  be  jacketed  either  from  the 
cooling  water  or  the  exhaust,  and  means  provided  for  increasing  the 
air  supply  to  prevent  the  motor  stopping  at  a  great  height  owing  to 
the  cold  and  the  rarefied  air.  The  reasons  for  this  have  been  gone 
into  more  at  length  under  the  heading  of  "Altitude."  With  these 
and  similar  improvements  that  will  be  suggested  by  experience  and 
further  accidents,  there  appears  to  be  no  reason  why  aviation  can 
not  be  made  as  safe  as  the  personal  equation  will  permit  it  to  be. 
There  will  always  be  reckless  flyers.  Ignorance  and  incompetence 
can  not  be  altogether  eliminated  any  more  than  they  can  in  sailing, 
hunting,  or  any  other  sport.  The  annual  hunting  fatalities  from 
these  causes  in  this  country  alone  make  a  total  beside  which  the 
aggregate  of  four  years  in  aviation  the  world  over,  is  but  an  insig- 
nificant fraction. 

Parachute  Garment  as  a  Safeguard.  To  save  as  many  as  pos- 
sible of  these  reckless  ones  from  themselves,  so  to  speak,  a  parachute 
garment  has  been  devised  to  ease  the  shock  of  the  fall.  It  will  be 
recalled  that  Voisin  would  not  fly  in  his  biplane  until  he  had  pro- 
vided himself  with  a  heavily-padded  helmet,  somewhat  on  the  order 
of  the  football  headpiece.  But  neither  a  padded  headpiece  nor  padded 
clothing  would  avail  much  against  a  fall  of  any  kind  from  an  aero- 
plane; hence,  the  parachute  garment.  Its  object  is  not  to  take  the 


690 


BUILDING  AND  FLYING  AN  AEROPLANE        125 

shock  of  a  fall,  as  are  the  pads,  nor  is  it  to  prevent  a  fall,  but  to  reduce 
the  rate-  of  drop  by  interposing  sufficient  air  resistance  to  make  the 
fall  safe.  This  new  parachute  is  in  the  form  of  a  loose  flowing  gar- 
ment, securely  fastened  to  the  body  and  fitted  over  a  framework 
carried  on  the  aviator's  back.  The  lower  ends  of  the  garment  are 
secured  to  the  ankles.  The  arrangement  is  such  that  when  the  aviator 
throws  out  his  arms,  the  garment  is  extended  somewhat  in  umbrella 
or  parachute  form,  thus  creating  sufficient  resistance  to  prevent  too 
rapid  a  descent.  Experiments  have  been  made  with  this  parachute 
dress  in  which  the  wearer  has  jumped  from  buildings,  cliffs,  and  other 
heights,  and  the  garment  has  assumed  its  role  of  parachute  at  once, 
permitting  a  safe  and  easy  descent. 

Study  of  Stresses  in  Fancy  Flying.  To  sum  up,  it  will  be  seen 
that  the  most  prolific  cause  of  fatalities  is  the  personal  equation. 
Of  all  the  many  dangers  encountered  in  aeroplaning,  one  of  the  most 
clearly  defined,  as  well  as  one  of  the  most  seductive,  results  from  fancy 
flying:  from  wheeling  round  sharp,  horizontal  curves;  from  conic 
spiraling;  from  cascading,  swooping,  and  undulating  in  vertical  plane 
curves,  popularly  dubbed  "stunts."  These  are  forms  of  flying  in 
which  aviators  constantly  vie  with  one  another.  They  frequently 
result  in  imposing  stresses  upon  the  machine  which  are  far  beyond 
its  capacity  to  withstand.  The  danger  is  particularly  alluring  to 
reckless  young  aviators  engaged  in  public  exhibitions.  The  death 
of  St.  Croix  Johnstone,  at  the  Chicago  Meet  in  the  summer  of  1911, 
affords  a  typical  illustration  of  what  may  be  expected  as  the  result 
of  such  performances^  Nevertheless,  partly  because  they  do  not 
adequately  appreciate  the  risk,  and  largely,  no  doubt,  because  of 
the  liberal  applause  accorded  by  an  admiring  throng  which  also  fails 
to  realize  the  hazardous  nature  of  the  fascinating  maneuvers,  there 
will  doubtless  always  be  aviators  to  undertake  such  feats. 

Singularly  enough,  the  exact  magnitude  of  such  hazards,  or 
more  accurately,  the  extent  of  the  increased  stress  in  the  machine, 
though  beyond  even  the  approximate  guess  of  the  aviator,  is  capable 
of  nice  computation  in  terms  of  the  speed  and  curvature  of  flight. 
During  an  exhibition  meet  in  Washington,  D.  C.,  during  the  summer 
of  1911,  Glenn  H.  Curtiss  found  difficulty  in  restraining  one  of  his 
young  pupils  from  executing  various  hair-raising  maneuvers.  He 
would  plunge  from  a  great  elevation  to  acquire  the  utmost  speed, 


691 


126         BUILDING  AND  FLYING  AN  AEROPLANE 

then  suddenly  rebound  and  shoot  far  aloft.  He  would  undulate  about 
the  field,  and  on  turns  would  bank  the  machine  until  the  wings 
appeared  to  stand  vertical.  Curtiss  solemnly  warned  the  young 
aviator  and  earnestly  restrained  him,  pointing  out  the  dangers  of 
sweeping  sharp  curves  at  high  speed,  of  swooping  at  such  dangerous 
angles,  and  the  like.  Curtiss  then  turned  to  A.  F.  Zahm  and  expressed 
the  wish  that  someone  would  determine  exactly  the  amount  of  the 
added  stress  in  curvilinear  flight.  The  following,  published  by  Zahm, 
in  the  Scientific  American,  gives  the  method  of  calculating  this: 

When  a  body  pursues  a  curvilinear  path  in  space,  the  centripetal  force 
urging  it  at  any  instant  may  be  expressed  by  the  equation 

Fn=m —    (absolute  units) 

m    V2 

= (gravitational  units) 

g    R 

in  which  Fn  is  the  centripetal  force,  jn  the  mass  of  the  body,  V  its  velocity, 
and  R  the  instantaneous  radius  of  curvature  of  the  path  followed  by  its  center 
of  mass.  Since  the  mass  may  be  regarded  as  constant  for  any  short  period, 
the  equation  may  be  expressed  by  the  following  simple  law: 

The  centripetal  force  varies  directly  as  the  square  of  the  velocity  of  flight 
and  inversely  as  the  instantaneous  radius  of  the  curvature  of  its  path. 

In  applying  the  above  equation  to  compute  the  stress  in  an 
aeroplane  of  given  mass  m,  we  may  assume  a  series  of  values  for 
V  and  72,  compute  the  corresponding  values  for  Fn,  and  tabulate 
the  results  for  reference.  Table  IV  has  been  obtained  in  this  manner. 
It  may  be  noted  that  on  substituting  in  the  equation,  V  is  taken  as 
representing  miles  per  hour,  R  as  feet,  and  g  as  22  miles  an  hour, 
in  order  to  simplify  the  figuring,  this  being  32.1  feet  per  second. 
The  table  shows  at  a  glance  the  centripetal  force  acting  on  an  aero- 
plane to  be  a  fractional  part  of  the  gravitational  force,  or  weight  of  the 
machine  and  its  load.  For  example,  if  the  aviator  is  rounding  a  curve 
of  300  feet  radius  at  60  miles  per  hour,  the  centripetal  force  is  0.55 
of  the  total  weight.  At  the  excessively  high  speed  of  100  miles  per 
hour  and  the  extremely  short  radius  of  100  feet,  the  centripetal  force 
would  be  4.55  times  the  weight  of  the  moving  mass.  The  pilot  would 
then  feel  heavier  on  his  seat  than  he  would  sitting  still  with  a  man 
of  his  own  weight  on  either  shoulder.  For  speeds  below  60  miles 
per  hour  and  radii  of  curvature  above  500  feet,  the  centripetal  force 
is  less  than  one  third  of  the  weight.  The  table  gives  values  for 
speeds  of  30  to  100  miles  per  hour,  by  increments  of  10  miles,  and  for 


692 


BUILDING  AND  FLYING  AN  AEROPLANE        127 


TABLE  IV 

Centripetal  Force  Acting  on  Aeroplane  at  Various  Speeds  and 
Curvatures  of  Flight 


(V)  Velocity 
or  Speed  of 

(R)    Radius  of  Curvature  in  Feet 

Aeroplane 

100                     200                     300                     400                     500 

Miles  per  hour 

Weight 

Weight 

Weight 

Weight 

Weight 

30 

0.41 

0.20 

0.14 

0.10 

0.08 

40 

0.73 

0.36 

0.24 

0.18 

0.15 

50 

1.14 

0.57 

0.38 

0.28 

0.23 

60 

1.64 

0.82 

0.55 

0.41 

0.33 

70 

2.23 

1.11 

0.74 

0.56 

0.45 

80 

2.91 

1.45 

0.97 

0.73 

0.58 

90 

3.68 

1.84 

1.23 

0.92 

0.74 

100 

4.55 

2.27 

1.52 

1.14 

0.91 

radii  of  curvature  of  100  to  500  feet,  by  increments  of  100  feet,  so 
that  intermediate  speeds  and  radii  may  readily  be  calculated. 

The  entire  stress  on  the  aeroplane  in  horizontal  flight,  being 
substantially  the  resultant  of  the  total  weight  and  the  centripetal 
force,  can  readily  be  figured  by  compounding  them.  Thus  in  hori- 
zontal wheeling,  the  resultant  force  as  shown  in  the  diagram,  Fig. 
50,  is  approximately 

F=  l/T 


In  swooping,  or  undulating  in  a  vertical  plane,  the  resultant 
force  at  the  bottom  of  the  curve  has  its  maximum  value 


w 


and  at  any  other  pdrt  of  the  vertical  path,  it  has  a  more  complex 
though  smaller  value,  which  need  not  be  given  in  detail. 

It  is  obvious  that  the  greatest  stress  on  the  machine  occurs  at 
the  bottom  of  a  swoop,  if  the  machine  be  made  to  rebound  on  a  sharp 
curve.  The  total  force  (Fn-\- 
W)  sustained  at  this  point  may 
be  found  from  the  table,  if  V 
and  R  be  known,  simply  by 
adding  1  to  the  figures  given, 

then      multiplying       by       the 

weight  of  the  machine.     For 

example,   if  the  speed   be   90   miles   per  hour  and  the  radius  of 


Fig.  50.     Force  Diagram  in  Horizontal  Wheeling 


693 


128         BUILDING  AND  FLYING  AN  AEROPLANE 

curvature  200  feet,  the  total  force  on  the  sustaining  surface  would 
be  2.84  times  the  total  weight  of  the  machine.  In  this  case,  the  stress 
on  all  parts  of  the  framing  would  be  2.84  times  its  value  in  level 
flight,  when  only  the  weight  has  to  be  sustained.  The  pilot  would 
feel  nearly  three  times  his  usual  weight. 

From  the  foregoing,  it  is  apparent  that  in  ordinary  banking 
at  moderate  speeds  on  moderate  curves,  the  additional  stress  due  to 
centripetal  force  is  usually  well  below  that  due  to  the  weight  of  the 
machine,  and  that  in  violent  flying,  the  added  stress  may  consider- 
ably exceed  that  due  to  the  weight  of  the  machine  and  may  accord- 
ingly be  dangerous,  unless  the  aeroplane  be  constructed  with  a  spe- 
cially high  factor  of  safety.  But  there  is  nothing  in  the  results  here 
obtained  that  seems  to  make  sharp  curving  and  swooping  prohibitive. 
If  the  framing  of  the  machine  be  given  an  extra  factor  of  safety,  at 
the  expense  perhaps  of  endurance  and  speed,  it  may  be  made  prac- 
tically unbreakable  by  such  maneuvers,  and  still  afford  to  the  pilot 
and  spectators  alike  all  the  pleasures  of  fantastic  flying. 

Methods  of  Making  Tests.  In  order  to  obtain  actual  data  for 
the  fluctuations  of  stress  in  an  aeroplane  in  varied  flying,  it  is  sug- 
gested that  the  stress  or 
strain  of  some  tension  or 


compression  member   of 
the  machine  be  recorded 

Fig.  51.     Method  of  Boxing  an  Acceleration  Recorder  . 

when  in  action;  or  simpler 

still,  perhaps,  that  a  record  of  the  aeroplane's  acceleration  be  taken 
and  particularly  its  transverse  acceleration.  A  very  simple  device  to 
reveal  the  transverse  acceleration  of  an  aeroplane  in  flight  would  be 
a  massive  index  elastically  supported.  A  lath  or  flat  bar  stretching 
lengthwise  of  the  machine,  one  end  fixed,  the  other  free  to  vibrate, 
and  carrying  a  pencil  along  a  vertical  chronograph  drum,  would 
serve  the  purpose.  This  could  be  protected  from  the  wind  by  a 
housing  as  shown  in  the  sketch,  Fig.  51. 

An  adjustable  sliding  weight  could  be  set  to  increase  or  diminish 
the  amplitude  of  the  tracing,  and  an  aerial  or  liquid  damper  could  be 
added  to  smooth  the  tracing.  The  zero  line  would  be  midway  between 
the  tracings  made  on  the  drum  by  the  stationary  instrument  when 
resting  alternately  in  its  normal  position  and  upside  down ;  the  distance 
between  this  zero  line  to  the  actual  tracing  of  the  stationary  instru- 


694 


BUILDING  AND  FLYING  AN  AEROPLANE        129 

ment  would  be  proportional  to  the  aeroplane  stresses  in  level,  rec- 
tilinear flight;  while  in  level  flight  on  a  curve,  either  horizontal  or 
vertical,  the  deviation  of  the  mean  tracing  from  the  zero  line  would 
indicate  the  actual  stress  during  such  accelerated  flight.  Of  course, 
the  drum  could  be  omitted  and  a  simple  scale  put  in  its  place,  so 
that  the  pilot  could  observe  the  mean  excursion  of  the  pencil  or  pointer 
from  instant  to  instant;  also,  the  damper  of  such  excursion  could 
be  adjusted  to  any  amount  in  the  proposed  instrument  if  the  vibrat- 
ing lath  fitted  its  encasing  box  closely  with  an  adjustable  passage 
for  the  air  as  it  moved  to  and  fro;  or  if  light  damping  wings  were 
added  to  the  lath,  or  flat  pencil  bar. 

Another  method  would  be  to  obtain  by  instantaneous  photog- 
raphy the  position  of  the  centroid  of  the  aeroplane  at  a  number  of 
successive  instants,  from  which  could  be  determined  its  speed  and 
path,  or  V  and  R  of  the  first  equation,  by  which  data,  therefore, 
the  stress  could  be  read  from  Table  IV. 

Perhaps  the  simplest  plan  would  be  to  add  an  acceleration  pen- 
holder, with  its  spring  and  damper,  to  any  recording  drum  the  aero- 
plane may  carry  for  recording  air  pressure,  temperature,  speed,  and 
so  forth.  Indeed,  all  such  records  could  be  taken  on  a  single  drum. 

A  score  of  devices,  more  or  less  simple,  but  suitable  for  reveal- 
ing the  varying  stress  in  an  aeroplane,  will  occur  to  any  engineer 
who  may  give  the  subject  attention.  And  it  is  desirable  in  the 
interests  both  of  aeroplane  design  and  of  prudent  manipulation  that 
someone  obtain  roughly  accurate  data  for  the  stresses  developed  in 
actual  flight.  ( 

Increment  of  Speed  in  Driving.  It  is  commonly  supposed  by 
aviators  that  the  increment  of  speed  due  to  driving  is  very  prodigious. 
An  easy  formula  will  determine  the  major  limit  of  such  speed  incre- 
ment. If  the  initial  and  natural  speed  of  the  aeroplane  be  v,  and 
the  change  of  level  in  diving  be  h,  while  the  speed  at  the  end  of  the 
dive  be  V,  the  minimum  change  of  level  necessary  to  acquire  any 
increment  of  speed,  V—  v,  may  be  found  from  the  equation 

(V-v) 
h=  — 

29 

If,  as  before,  g  be  taken  as  22  miles  per  hour,  the  equation  reduces 


695 


130         BUILDING  AND  FLYING  AN  AEROPLANE 

TABLE  V 

Minimum  Change  of  Level  Necessary  to  Produce  Various  Speed 

Increments 


Natural  Speed  v 
of  the  Aeroplane 

Increments  of  Speed  V  —  v 
Miles  per  hour,  10           Miles  per  hour,  20            Miles  per  hour,  30 

Miles  per  hour 

Feet 

Feet 

Feet 

30 

23.3 

53.3 

90.0 

40 

30.0 

66.7 

110.0 

50 

36.7 

80.0 

130.0 

60 

43.3 

93.3 

150.0 

70 

50.0 

106.7 

170.0 

to  the  convenient  formula 


30 

in  which  V  and  v  are  taken  in  miles  per  hour.  Assuming  various 
values  for  V  and  v,  Table  V  has  been  found  for  the  corresponding 
values  of  h  in  feet:  For  example,  if  the  natural  speed  of  the  aero- 
plane in  level  flight  be  50  miles  per  hour,  and  the  aviator  wishes  to 
increase  the  speed  by  20  miles  per  hour,  he  must  dive  at  least  80 
feet,  assuming  that  the  aeroplane  falls  freely,  like  a  body  in  vacuo,  or 
that  its  propeller  overcomes  the  air  resistance  completely;  other- 
wise the  fall  must  be  rather  more  than  80  feet. 

It  has  been  suggested  that  a  contest  be  arranged  to  determine 
which  aviator  could  dive  most  swiftly  and  rebound  most  suddenly, 
the  prize  going  to  the  one  who  should  stress  his  machine  most  as 
indicated  by  the  accelerograph  above  proposed.  But  to  avoid  dan- 
ger, the  contest  would  have  to  be  supervised  by  competent  experi- 
mentalists, and  would  be  best  conducted  over  water.  It  is  safe  to  say 
that  more  than  one  well-known  aeroplane  would  be  denied  entry  in 
such  a  contest  because  of  lack  of  a  sufficient  factor  of  safety  in  its 
construction. 

Dirigible  Accidents.  Because  its  wrecks  are  spectacular  and 
the  loss  involved  tremendous,  the  dirigible  has  probably  earned  an 
undeserved  reputation,  though  it  must  be  admitted  that  the  big 
airships  have  come  to  grief  with  surprising  regularity.  The  fact 
must  be  noted,  however,  that  when  an  aeroplane  is  wrecked,  the 


696 


BUILDING  AND  FLYING  AN  AEROPLANE        131 

aviator  seldom  escapes  with  his  life,  while  the  spectators'  lives  are 
endangered  to  an  even  greater  extent,  whereas  in  the  case  of  the 
dirigible,  the  loss  is  simply  financial,  both  the  crew  and  passengers 
usually  escaping  without  a  scratch.  This  is  largely  due  to  the  fact 
that  the  majority  of  accidents  to  dirigibles  have  happened  on  the 
ground,  and  have  been  caused  by  lack  of  facilities  for  properly 
handling  or  "docking"  the  huge  gas  bag.  Of  course,  lack  of  flotation 
or  an  accident  to  the  motors,  or  both  combined,  have  brought  two 
of  the  numerous  Zeppelins  to  earth  in  a  very  hazardous  manner, 
though  no  one  was  killed,  while  four  French  army  officers  lost  their 
lives  in  the  Republique  disaster,  the  exact  cause  of  which  was  never 
definitely  ascertained.  This  was  likewise  the  case  with  Erbsloeh 
and  his  companion  who  were  dropped  from  the  sky,  their  airship 
having  taken  fire.  It  was  thought  that  ignition  was  caused  by  atmos- 
pheric electricity,  in  this  instance. 

By  far  the  great  majority  of  later  dirigible  accidents  have  been 
due  solely  to  the  crude  methods  of  handling  the  airships  on  the 
ground,  and  the  frequency  with  which  these  have  occurred  should 
certainly  have  been  responsible  for  the  adoption  of  improvements 
in  this  respect  at  an  earlier  day. 

For  instance,  the  Morning  Post,  a  big  Lebaudy  type  bought 
for  English  use,  had  the  envelope  ripped  open  by  an  iron  girder  pro- 
jecting from  its  shed.  Repairs  took  several  months,  and  at  the  end 
of  the  first  trial  thereafter,  the  ship  was  again  wrecked  in  landing.  A 
company  of  soldiers  failed  to  hold  the  big  craft  and  it  drifted  broad- 
side into  a  clump  of  trees,  hopelessly  wrecking  it.  In  attempting  to 
dock  the  Deutschland  I,  200  men  were  unable  to  hold  it  down,  a 
heavy  gust  of  wind  catching  the  big  airship  and  pounding  it  down 
on  top  of  a  wind  break  that  had  been  specially  erected  at  the  entrance 
of  the  shed  for  protection.  A  similar  accident  happened  to  the  big 
Parseval,  a  violent  gust  of  wind  casting  it  against  the  shed  and  tearing 
such  a  hole  in  the  envelope  that  the  gas  rushed  out  and  the  car 
dropped  30  feet  to  the  ground.  The  big  British  naval  dirigible  of  the 
rigid  type,  the  Mayfly,  was  broken  in  half  in  attempting  to  take  it 
out  of  the  shed  the  first  time.  A  cross  wind  was  blowing  and  the 
gas  bag  of  one  of  the  central  sections  was  torn,  deflating  it  and  show- 
ing in  a  striking  manner  that  the  solidity  of  a  rigid  dirigible  results 
chiefly  from  the  aerostatic  pressure  of  the  gas  in  its  various  compart- 


697 


132        BUILDING  AND  PLYING  AN  AEROPLANE 

ments.  Without  the  gas  lift,  a  rigid  frame  is  so  in  reality  only  for 
certain  limited  distances,  as  was  shown  by  the  total  collapse  of  the 
Mayfly's  frame  after  having  been  subjected  to  the  opposed  leverage 
of  the  parts  on  either  side  of  the  original  break.  This,  of  course, 
was  an  error  in  design,  as  the  frame  of  a  rigid  dirigible  should  cer- 
tainly not  be  so  weak  in  itself  as  to  collapse  upon  the  deflation  of  a* 
single  one  of  the  central  compartments.  The  incident  on  the  trip  of 
the  Zeppelin  III  to  Berlin,  in  1909,  when  the  flying  blades  of  a  broken 
propeller  pierced  the  hull  without  causing  an  accident,  shows  how 
much  resistance  it  may  offer. 

AMATEUR  AVIATORS 

It  will  probably  come  as  a  surprise  to  the  average  reader  to 
learn  that  at  the  end  of  1910,  there  were  more  than  a  thousand  ama- 
teur aviators  in  this  country,  though  all  the  flights  which  form  the 
subject  of  newspaper  reports  have  been  the  work  of  not  more  than 
a  dozen  flyers  and  doubtless  half  the  population  has  not  as  yet  seen 
an  aeroplane  in  flight.  The  desire  to  fly,  whether  it  be  to  satisfy  one's 
desire  to  soar  above  the  world  in  seeming  defiance  of  natural  laws, 
or  merely  to  obtain  the  financial  reward  that  is  won  by  successful 
flight,  attracts  a  great  many  from  all  stations  and  walks  of  life.  This 
is  particularly  true  among  older  boys  who  look  on  aviation  as  an 
advanced  form  of  kite-flying.  An  example  of  rather  serious  work 
along  this  line  may  be  cited  of  two  high  school  boys  of  Chicago, 
Harold  Turner  and  Fred  Croll,  who  built  a  monoplane  weighing  125 
pounds,  Fig.  52.  This  machine,  although  too  small  for  a  motor, 
was  equipped  with  rudder  and  other  operating  planes  and  levers, 
the  elevating  plane  and  ailerons  being  automatically  operated  by 
an  electrical  device.  On  one  of  its  flights  the  machine,  carrying  a 
120-pound  operator,  was  started  and  propelled  by  attaching  it  to  an 
automobile;  it  rose  to  a  height  of  15  feet,  and  remained  in  the  air  43 
seconds. 

Contrary  to  all  precedent,  the  average  amateur  is  bent  upon 
achieving  what  the  skilled  professional  considers  as  beyond  even 
his  talent  and  resources — that  of  building  his  own  flying  machine. 
With  every  other  mechanical  vehicle,  the  amateur  learns  to  drive  first 
and  the  majority  are  content  with  that  achievement — for  example, 
very  few  chauffeurs  have  any  great  ambition  to  build  their  own 


698 


BUILDING  AND  FLYING  AN  AEROPLANE         133 

automobiles.  With  flying  machines  (one  of  the  most  difficult  of 
mechanical  contrivances),  nearly  all  amateurs  want  to  construct 
new  types  for  themselves  and  all  confidently  expect  to  fly  with 
no  more  knowledge  than  that  gained  in  constructing  them.  We  all 
have  to  be  apprentices  before  becoming  masters,  so  all  aviators  neces- 
sarily have  to  be  learners  and  "grass  cutters"  before  being  professionals. 
Charles  K.  Hamilton  was  an  exception,  but  he  was  already  an  expert 
pilot  of  dirigible  balloons,  and  he  did  not  try  to  build  his  own  aero- 
plane. Willard,  Mars,  and  Ely,  all  Curtiss  pupils,  flew  after  a  very 
short  training,  but  they  did  not  attempt  to  construct  aeroplanes  for 


Fig.  52.     What  an  Amateur  Aviator  Can  Do  in  Building  an  Aeroplane 

themselves.    This  is  also  true  of  Clifford  B.  Harmon,  the  champion 
amateur. 

Classes  of  Amateurs.  Inventors.  Generally  speaking,  ama- 
teurs are  of  two  classes.  Those  of  the  first  class  believe  they  have 
conceived  some  entirely  new  system  or  invention,  or  an  improve- 
ment on  some  machine  that  has  previously  proved  a  failure;  they 
think  they  have  discovered  the  secret  which  other  inventors  who 
preceded  them  failed  to  grasp.  They  expend  their  meager  capital 
in  trying  to  realize  high  hopes.  A  comparatively  small  number 
ever  get  as  far  as  completing  the  machine  and  one  trial  on  the  field 
is  usually  sufficient  to  put  a  quietus  on  those  who  do,  as  it  is  disap- 
pointing, to  say  the  least,  to  see  the  result  of  a  number  of  months' 


699 


134         BUILDING  AND  FLYING  AN  AEROPLANE 

work  undone  in  a  twinkling  without  the  machine  having  shown  the 
least  disposition  or  ability  to  get  off  terra  firma. 

Would-Be  Performers.  The  second  class  finds  its  chief  incen- 
tive in  the  munificent  reward  to  be  gained  with  what  appears  to  be 
comparatively  little  effort  or  expenditure,  and  the  amateur  who  is 
seeking  financial  returns  has  no  alternative  except  to  build  his  own 
machine,  or  enter  either  the  Wright  or  Curtiss  school  of  flying  and 
secure  a  berth  with  one  of  these  companies. 

Wright  and  Curtiss  Patents.  This  is  the  result  of  conditions 
at  present  obtaining  in  the  field  of  aviation.  The  only  generally 
successful  types  of  American  aeroplanes  are  the  Wright  and  Curtiss, 
and  the  acquirement  of  a  biplane  of  either  type  means  the  expendi- 
ture of  at  least  $5,000  for  the  machine  alone,  and  they  are  sold  only 
to  individuals  on  the  express  condition  that  the  machines  are  not 
to  be  used  for  exhibition  or  as  a  means  of  profit  to  the  owner.  The 
manufacturers  have  expert  flyers  of  their  own  who  attend  meets 
and  fairs  throughout  the  country.  It  would  make  their  monopoly 
impossible  to  allow  outsiders  to  fly  their  aeroplanes  publicly  or  to 
exhibit  them.  By  this  restriction  the  price  of  the  machines  is  kept 
up  and  large  returns  are  gained  by  exhibitions  and  flying. 

To  break  this  monopoly  by  importing  European  machines  is 
not  possible.  All  the  successful  aeroplanes  made  abroad  such  as  the 
Farman,  Cody,  and  Sommer  biplanes;  and  the  Bleriot,  Antoinette, 
and  Grade  monoplanes  are  fitted  with  devices  of  control  or  stability, 
or  both,  covered  by  the  Wright  patents  and  can  not  be  flown  in  this 
country  without  legal  trouble.  The  numerous  foreign  aviators 
who  brought  over  their  machines  in  the  fall  of  1910  to  compete  at 
the  International  Meet,  did  so  only  on  being  granted  a  concession 
by  the  Wright  Company  to  the  effect  that  they  would  not  be  con- 
sidered as  infringers  and  sued.  Similar  arrangements  were  made  at 
subsequent  meets  and  this  handicap  will  always  be  present  where 
foreign  machines  are  used. 

Evasion  by  Invention  of  New  Types.  But  when  he  thinks  of 
the  unprecedented  sums  paid  professionals  for  simply  exhibiting 
their  machines  and  making  short  flights,  the  amateur  is  anxious  to 
obtain  a  share  of  the  profits.  No  thought  is  given  the  fact  that  were 
he  and  all  his  kind  permitted  to  fly,  the  achievement  would  soon 
be  commonplace  and  the  aviator's  golden  age  would  be  over.  There 


700 


BUILDING  AND  FLYING  AN  AEROPLANE        135 

are  accordingly  hundreds  of  would-be  aviators  in  this  country  today 
who  are  striving  to  evade  the  Wright  basic  patents  by  either  devis- 
ing entirely  new  types  of  aeroplanes,  or  by  inventing  new  methods 
of  control  and  stability  that  will  not  infringe.  Others,  reasoning 
that  the  old  aeroplanes  built  before  the  advent  of  the  Wright  machine 
cannot  be  held  as  infringements  owing  to  priority,  propose  to  develop 
Maxim,  Langley,  and  Ader  machines,  though  the  dictum  in  the 
New  York  Court  of  Appeals  decision  referred  to  under  the  head  of 
"Legal  Status  of  Wright  Patent,"  which  states  that  a  prior  machine 
which  had  never  been  known  to  fly  would  not  be  considered  an  antici- 
pation of  a  modern  successful  machine,  may  prove  a  stumbling  block 
in  their  case  as  well.  Thus,  a  round  of  the  workshops  of  these  enthu- 
siasts reveals  a  host  of  heavier-than-air  machines  of  every  conceiv- 
able type  and  shape,  every  one  of  which,  according  to  its  builder, 
is  an  aeroplane  that  will  fly.  Mineola  and  Garden  City,  Long  Island, 
harbor  a  score  of  these  little  shops  the  year  round,  but  the  same 
scenes  are  being  enacted  on  a  smaller  scale  in  almost  every  state  in 
the  Union,  and  particularly  in  California,  Ohio,  Kansas,  Massachu- 
setts, and  Arizona,  in  addition  to  which  there  are  many  who  are 
carrying  their  experiments  on  in  secret.  Each  believes  deep  in  his 
heart  that  he  will  succeed  where  a  master  failed. 

"Maxim  failed  with  this  type  of  machine,"  quotes  one.  "How 
did  he  expect  to  fly  when  his  control  was  not  proportionate,  to  the 
machine's  lift  capacity?"  Seemingly,  nobody  ever  thought  of  that 
and  our  friend  will  make  a  fortune  by  going  Maxim  one  better,  but 
he  does  not.  After  months  of  labor  and  a  great  deal  of  expense  he 
finds  that  some  unforeseen  difficulty  develops  which  keeps  his 
machine  to  earth  as  if  it  were  part  and  parcel  of  it.  Another  has 
conceived  a  type  of  monoplane  that  is  entirely  new — different  from 
any  existing  type — and  as  the  latter  are  all  foreign,  he  prides  him- 
self on  having  developed  a  monoplane  that  will  be  entirely  Ameri- 
can— the  first  and  only  American  monoplane.  Theoretically,  it  is  a 
wonder;  mechanically  it  is  correct;  and  it  speeds  over  the  turf  with 
surprising  velocity;  but  when  the  elevating  rudder  is  operated  to 
make  the  machine  rise,  it  balks  and  plunges  head  first  into  the 
ground.  Again  and  again,  the  propeller  and  other  broken  parts 
are  replaced  at  no  small  expense ;  again  and  again  the  inventor  goes 
over  every  part  of  the  machinery  and  computes  the  dimensions  of 


701 


136        BUILDING  AND  FLYING  AN  AEROPLANE 

the  supporting  surface  to  see  if  it  all  corresponds  with  the  formula 
of  his  special  theory.  But  time  after  time,  the  aeroplane  acts  like  a 
jumping  frog  and  lands  head  first.  At  last,  its  builder  becomes  con- 
vinced that  there  is  something  radically  wrong  and  begins  to  depart 
from  his  original  plans,  involving  changes  that  simply  mean  a  waste 
of  effort  and  money,  since  the  inventor  does  not  himself  know  what 
he  is  trying  to  correct  and  no  one  else  knows  better  than  he  what 
the  trouble  is. 

Evasion  by  Acquiring  European  Types.  Others  still,  realizing 
from  the  foregoing  experiences  that  it  is  almost  impossible  to  con- 
struct an  entirely  new  type  of  aeroplane  off-hand,  acquire  European 
types  and  propose  to  fit  them  with  new  control  and  stability  devices, 
such  as  are  not  covered  by  the  Wright  patents.  So  far,  none  has 
succeeded.  Somehow,  the  Wrights  seem  to  have  covered  all  the 
conceivable  working  devices  for  control  and  stability,  and  the  numer- 
ous attempts  have  accordingly  resulted  in  failure.  Undoubtedly, 
some  of  these  aeroplanes  built  by  amateurs  may  really  be  capable 
of  flight;  but  how  is  the  inventor  to  know  it  when  he  lacks  the  ability 
to  operate  it?  To  know  how  to  fly  an  aeroplane  is  a  condition  prece- 
dent to  success  in  the  field  of  aviation  that  can  not  be  met  by  build- 
ing of  a  machine.  The  beginner  is  thus  badly  handicapped.  Even 
though  his  machine  may  embody  the  elements  essential  to  success- 
ful flight,  he  may  never  be  able  to  establish  the  fact,  since  his  first 
blundering  attempt  or  two  frequently  ends  by  wrecking  the  machine, 
and  many  have  neither  the  means  nor  the  stamina  to  persevere  fur- 
ther after  a  few  bad  wrecks,  involving  weeks  and  weeks  of  rebuilding 
each  time.  He  can  not  engage  an  expert  to  fly  his  machine  for  him, 
as  the  expert's  time  per  minute  figures  out  a  price  that  makes  him 
gasp,  and  even  at  that  the  expert  professional's  time  is  pretty  much 
all  taken.  Furthermore,  very  few  would  run  the  risk  of  attempting 
to  fly  an  untried  aeroplane — they  have  more  to  lose  through  acci- 
dental injury  than  the  builder  has  through  the  failure  of  his  theories. 

And  so  it  is  with  most  inventors.  They  may  have  conceived 
something  really  good,  but  it  is  not  complete,  and  an  aeroplane  is 
hardly  worth  its  weight  as  junk  unless  it  is.  Hundreds  of  patents 
are  taken  out  every  year  on  devices  to  be  used  on  heavier-than-air 
machines;  inventors  by  scores  make  daily  rounds  trying  to  interest 
financiers  in  some  seemingly  wonderful  mechanical  scheme,  and 


703 


BUILDING  AND  FLYING  AN  AEROPLANE        137 

dozens  of  companies  are  organized  each  year  to  exploit  some  espe- 
cially promising  inventions.  Numbers  of  aeroplanes  are  constructed 
and  hailed  as  marvels,  but,  somehow,  when  a  successful  flight  is  made 
by  an  amateur  it  is  always  with  some  standard  aeroplane,  either  of 
the  Curtiss  or  Farman  types,  and  mostly  the  former.  In  fact,  the 
Curtiss  has  become  a  favorite  with  the  amateur  since  the  Federal 
court  refused  to  sustain  the  granting  of  a  preliminary  injunction  in 
favor  of  the  Wright  Company  against  Glenn  H.  Curtiss.  It  is  accord- 
ingly being  taken  for  granted  in  general  that  the  outcome  of  the 
Wright  vs.  Curtiss  litigation  will  be  to  declare  the  Curtiss  machine 
non-infringing.  Should  it  be  the  other  way  about,  there  will  certainly 
be  gloom  and  despair  in  the  amateur  camps  throughout  the  country. 
However,  neither  the  Wrights  nor  Curtiss  impose  any  restriction 
upon  the  building  of  machines  of  their  types  for  experimental  pur- 
poses, so  that  the  amateur  who  wishes  to  copy  them  may  safely  do 
so,  provided  no  attempt  be  made  to  employ  the  machine  for  pur- 
poses of  public  exhibition  or  financial  gain. 


703 


AVIATION  AND  ITS  FUTURE 

DIRIGIBLE   VS.   AEROPLANE 

While  interest,  to  a  great  extent,  is  monopolized  by  the  achieve- 
ments of  the  aeroplane,  opinion  is  still  more  or  less  divided  as  to  the 
merits  of  the  two  methods  of  navigating  the  air — the  lighter-than- 
air  (the  dirigible)  or  the  heavier-than-air  (the  aeroplane).  Though 
greatly  in  the  minority,  those  who  contend  for  the  advantages  of 
the  dirigible  are  none  the  less  convinced  that,  in  the  final  analysis, 
it  will  be  the  airship  rather  than  the  flying  machine  which  will  reign 
supreme.  From  this  standpoint,  the  aeroplane  is  regarded  as  a 
mere  scientific  toy  of  rather  doubtful  utility.  The  advocates  of  the 
flying  machine,  on  the  other  hand,  look  upon  the  dirigible  as  a  huge, 
unwieldy,  and  prohibitively  costly  construction,  the  futility  of  which 
as*  a  successful  means  of  navigating  the  air  will  be  fully  realized  by 
reason  of  the  development  of  the  aeroplane  within  the  next  few  years. 
Between  these  wholly  irreconcilable  opinions,  there  is  a  middle 
ground  taken  by  those  who  regard  both  as  being  of  value  in  their 
particular  spheres,  and  who  think  further  that  both  will  endure  and 
develop  contemporaneously.  By  briefly  summarizing  the  advan- 
tages and  disadvantages  of  each,  the  reader  will  be  given  an  oppor- 
tunity to  judge  for  himself. 

Dirigible.  Advantages.  One  of  the  chief  advantages  claimed 
for  dirigibles  is  their  ability  to  take  aloft  comparatively  heavy 
loads — weights  far  beyond  the  capacity  of  the  largest  aeroplanes  so 
far  constructed.  This  great  carrying  capacity  permits  of  transport- 
ing large  quantities  of  supplies  and  fuel  and  a  large  crew,  with  the 
added  advantage  of  permitting  the  latter  a  certain  range  of  move- 
ment about  the  airship  while  it  is  in  flight — the  aeroplanist  or  his  pas- 
senger naturally  can  not  stir  from  their  seats.  But  of  greater  value 
than  this — particularly  for  military  purposes,  to  which  the  dirigible 
is  almost  wholly  adapted  at  present — is  its  ability  to  remain  motion- 
less over  the  field  of  action  in  a  calm,  or  by  using  its  engines  to  coun- 

Copyright,  1912,  by  American  School  of  Correspondence. 


705 


706 


AVIATION  AND   ITS   FUTURE  3 

teract  a  head  wind  which  is  within  its  capacity  to  resist.  Moreover, 
it  is  capable  of  remaining  aloft  and  of  traveling  with  the  wind  even 
after  its  fuel  supply  is  exhausted,  and  in  fair  weather  it  can  keep  to 
the  air  for  a  much  longer  period  than  the  aeroplane. 

Disadvantages.  In  the  first  place,  the  initial  cost  of  building  a 
dirigible  of  sufficient  size  to  be  of  any  practical  use  is  so  great  as  to 
limit  its  utilization  largely  to  military  operations,  though  a  number 
of  dirigibles  are  being  built  in  Germany  by  commercial  companies 
for  passenger  carrying.  Few  but  national  governments  can  afford 
to  build  dirigibles,  Wellman's  ill-fated  America,  which  was  small 
as  compared  with  the  military  dirigibles  of  the  European  govern- 
ments, cost  something  like  $100,000  to  build  and  equip.  Its  main- 
tenance is  even  more  costly.  The  temporary  shed  to  house  the 
America  cost  $10,000  to  erect  and  $5,000  was  spent  in  inflating  the 
airship  once.  To  propel  it,  using  full  power,  about  200  gallons  of 
gasoline  a  day  was  necessary,  with  a  proportionately  large  supply 
of  oil.  As  its  speed  was  low,  there  would  be  frequent  occasions 
when  the  engines  would  have  to  be  run  at  their  full  capacity,  simply 
to  prevent  it  from  being  carried  away  by  the  wind,  while  there  would 
also  be  a  number  of  days  in  the  year  when  it  could  not  safely  be 
taken  out  of  the  shed. 

To  erect  a  permanent  building  to  sheicer  one  of  the  large  Euro- 
pean military  dirigibles  involves  an  outlay  sufficient  to  pay  for  a 
whole  fleet  of  aeroplanes,  and  the  huge  gas  bag  is  never  safe  outside 
of  its  home.  While  an  aeroplane  can  land  on  a  city  street  and  rise 
again,  Fig.  1,  nothing  short  of  a  twenty-acre  field  provides  a  safe 
landing  place  for  a  dirigible,  and  the  operation  is  a  delicate  one  even 
under  the  most  favorable  conditions,  so  much  so,  that  the  shed  to 
house  the  various  Zeppelin  airships  was  anchored  at  first  on  Lake 
Constance  in  order  that  the  dirigible  always  might  enter  it  against 
the  wind.  In  view  of  the  great  expense  involved  in  providing  accom- 
modation for  it,  the  airship  is  usually  compelled  to  operate  from 
a  limited  number  of  fixed  bases,  to  one  of  which  it  must  return.  In 
case  a  high  wind  should  spring  up  when  it  is  aloft,  it  is  equally  dan- 
gerous to  stay  in  the  air  or  to  attempt  to  land,  and  it  may  frequently 
happen  that  the  force  of  the  wind  is  so  great  that  the  airship  can  not 
reach  its  base  at  all,  or  it  is  blown  away  from  its  landing  place  before 
the  numerous  attendants  necessary  can  get  it  under  shelter.  This 


707 


4  AVIATION  AND  ITS   FUTURE 

last  has  happened  \o  French  military  airships  on  two  occasions, 
while  the  Zeppelin  dirigibles  that  have  come  to  grief  through  being 
blown  to  pieces  against  the  ground  form  a  striking  illustration  of  one 
of  the  chief  dangers  to  which  the  tremendously  unwieldy  apparatus 
has  been  subject,  but  which  is  now  greatly  reduced  by  improved 
methods  of  handling. 

Aloft,  it  is  surrounded  by  perils,  both  from  within  and  without. 
The  close  proximity  of  such  a  huge  quantity  of  highly  inflammable 
gas  to  the  gasoline  engines  or  other  sources  of  fire  renders  its  opera- 
tion risky,  to  say  the  least,  while  it  is  equally  exposed  to  fire  or  explo- 
sion through  being  out  in  an  electrical  storm,  it  being  the  general 
consensus  of  opinion  that  lightning,  or  an  electrical  discharge  caused 
by  the  high  difference  of  potential  between  the  atmosphere  and  the 
gas  bag  and  metal  parts  of  the  airship,  caused  the  explosion  which 
ended  the  lives  of  Oscar  Erbsloh  and  his  five  companions  in  one  of 
the  German  military  airships  in  the  summer  of  1910.  As  explained 
under  ''Wireless  on  Aeroplane  and  Airship,"  it  is  not  necessary  that 
the  airship  itself  should  be  actually  struck  by  lightning  to  bring 
about  this  discharge,  although  it  offers  a  powerful  attraction;  its 
mere  presence  at  a  height  where  the  atmosphere  is  heavily  charged, 
being  sufficient  to  create  electrical  discharges  capable  of  setting  fire 
to  the  gas  or  to  the  envelope. 

Mention  has  already  been  made  of  the  fact  that  to  be  of  any 
use,  the  dirigible  must  be  planned  on  an  enormous  scale,  with  a  cor- 
respondingly disproportionate  increase  in  the  amount  of  gas  required 
to  inflate  it  and  the  power  needed  to  drive  it.  Consequently,  it  has 
been  found  impossible  to  attain  speeds  in  excess  of  43  miles  an  hour, 
and  only  one  airship  at  present  in  use  abroad  is  capable  of  going 
that  fast.  Even  with  the  most  impermeable  fabrics  that  can  be 
manufactured  there  is  more  or  less  leakage  of  gas,  but  more  serious 
than  this  by  far  is  the  loss  attendant  upon  ascending  and  descend- 
ing. Skillful  and  rapid  manipulation  is  frequently  necessary  to 
prevent  rising  suddenly  to  great  heights  through  temperature  changes, 
which  occasions  the  loss  of  considerable  hydrogen  in  order  to  return 
to  earth  again,  while  cloudy  weather  and  particularly  the  sudden 
advent  of  rain  brings  about  an  alarming  contraction  in  the  envelope. 
Reference  to  Wellman's  experiences  with  the  America  will  reveal 
how  precarious  an  undertaking  the  keeping  an  airship  aloft  over 


708 


AVIATION  AND  ITS   FUTURE  5 

night  is,  the  loss  of  lifting  power  through  the  drop  in  the  tempera- 
ture being  so  great  as  to  seriously  imperil  its  safety.  Add  to  this  the 
necessity  of  returning  to  its  base  of  operation  in  order  to  be  safely 
housed  against  the  wind  when  on  the  ground,  and  it  will  be  appar- 
ent that  the  dirigible  is  very  much  of  a  fairweather  craft,  though  the 
German  army  dirigibles  are  said  to  be  used  frequently  for  night 
trips. 

Large  Radius  of  Action.  To  offset  this  formidable  list  of  weak- 
nesses and  disadvantages,  it  may  be  pointed  out  that  the  airship 
has  accomplished  some  wonderful  trips,  seemingly  all  the  more 
wonderful  because  at  the  time  of  their  execution  there  were  no  other 
performances  to  compare  them  with.  But  upon  referring  to  the 
circumstances  under  which  they  have  been  carried  out,  it  will  be 
found  that  they  were  usually  under  the  most  favorable  conditions. 
The  weather  was  favorable,  the  wind  never  in  excess  of  35  miles  an 
hour,  and  the  entire  trip  was  of  necessity  completed  during  daylight, 
usually  between  dawn  and  8  p.  M.,  when  the  temperature  range  is 
not  so  great  as  seriously  to  affect  the  lifting  capacity.  While  capa- 
ble of  carrying  aloft  a  greater  number  than  can  as  yet  be  approached 
by  the  aeroplane,  it  is  likewise  necessary  to  carry  a  much  greater 
crew,  so  that  the  actual  passenger-carrying  capacity  is  much  less 
than  that  of  the  aeroplane  in  proportion  to  size.  Whether  the  latter 
has,  as  its  sole  freight,  the  aviator  himself,  or  carries  eight  passengers, 
as  in  the  case  of  the  Bleriot  "bus,"  the  entire  control  is  centered  in 
one  man.  However,  the  dirigible  has  the  inestimable  advantage 
of  providing  direct  access  to  the  motors,  so  that  they  can  be  restarted, 
and  the  further  advantage  of  being  able  to  stop  its  motors  and  still 
remain  aloft. 

Aeroplane.  Cost.  In  summarizing  the  advantages  and  disad- 
vantages of  the  aeroplane  in  a  similar  manner,  the  first  considera- 
tion is  naturally  that  of  cost — both  initial  and  subsequent.  Taking 
the  cost  of  a  good  two-man  machine  as  $5,000,  the  price  at  which 
the  Wright  biplane  lists  in  this  country,  it  will  be  seen  that  100  of 
these  machines  can  be  placed  in  the  field  for  the  price  of  but  a  single 
Zeppelin  dirigible,  which  is  said  to  cost  $500,000.  The  expense  of 
the  initial  inflation  of  such  an  airship  represents  the  equivalent  of 
another  aeroplane,  while  its  bill  for  fuel  would  keep  a  great  many  of 
them  in  the  air,  and  the  cost  of  a  shed  for  housing  it  would  mean 


709 


6  AVIATION  AND  ITS  FUTURE 

probably  ten  more,  as  a  huge  permanent  building  of  the  size  required 
involves  close  to  an  outlay  of  $50,000.  On  the  question  of  expense, 
therefore,  the  dirigible  is  hopelessly  at  a  disadvantage,  and  as  its 
value  as  to  carrying  power  is  in  direct  proportion  to  its  size,  this 
must  always  be  the  case. 

Speed.  •  No  comparison  is  possible  where  speed  is  concerned  for 
the  slowest  aeroplane  travels  as  fast  or  faster  than  the  most  speedy 
dirigible — about  43  miles  an  hour — while  speeds  in  excess  of  99  miles 
an  hour  already  have  been  reached  by  the  aeroplane  with  every 
prospect  that,  with  the  developments  of  the  next  few  years,  the  speed 
of  flight  will  be  materially  increased. 

Strategic  Advantages.  Any  strategic  advantages  the  use  of  the 
dirigible  might  possess  vanish  completely  in  the  face  of  such  supe- 
riority in  speed,  which  means  a  proportionately  greater  ease  of  maneu- 
vering. There  appears  to  be  no  reason  why  one  $5,000  aeroplane 
could  not  easily  be  the  means  of  destroying  a  $500,000  dirigible  in 
time  of  war,  while  if  beset  by  a  fleet  of  these  high-speed  flyers,  its 
destruction  would  be  inevitable.  The  huge  gas  bag  of  an  airship 
forms  a  mark  that  would  be  difficult  to  miss  and  even  small  arm 
fire  would  quickly  destroy  the  value  of  the  envelope  as  a  supporting 
medium.  The  wings  of  an  aeroplane,  on  the  other  hand,  could  be 
riddled  with  bullets  without  seriously  impairing  its  ability  to  stay 
aloft.  Now  that  the  only  limit  to  altitude  flights  is  the  aviator's 
endurance,  there  could  be  no  possible  escape  for  the  dirigible. 
Although  the  latter,  by  the  sudden  release  of  ballast,  can  shoot  up 
to  great  heights,  the  aeroplane  can  rapidly  follow,  as  shown  by  John- 
stone's  flight  to  a  height  of  more  than  9,000  feet  in  a  little  over  25 
minutes,  and  the  crew  of  the  dirigible  is  quite  as  susceptible  to  the 
physiological  effects  of  the  sudden  change  of  barometric  pressure 
as  is  the  operator  of  an  aeroplane — more  so,  in  fact,  as  the  change 
may  be  more  sudden. 

Passenger  Service.  Where  passenger  carrying  is  ^concerned, 
the  developments  of  the  past  year  show  conclusively  that  the  aero- 
plane can  be  given  more  than  sufficient  capacity  for  all  military  pur- 
poses. Breguet  has  succeeded  in  carrying  twelve  passengers  in  a 
comparatively  moderate-sized  machine,  a  number  which  can  undoubt- 
edly be  increased,  so  that  with  its  greater  speed  the  aeroplane  can 
more  than  compete  with  the  dirigible  as  a  passenger  carrier.  It 


710 


AVIATION  AND   ITS   FUTURE  7 

does  not  require  a  regiment  of  men  to  help  it  alight  or  get  away,  and 
a  small  building  will  house  it.  If  necessary  to  stow  it  in  a  restricted 
space,  this  may  be  done  by  dismounting  the  wings,  the  reverse 
process  of  assembling  being  so  simple  that  the  machine  can  be  made 
ready  for  service  in  an  hour's  time. 

Behavior  in  a  Wind.  When  the  aeroplane  first  came  into 
prominence  several  years  ago,  its  then  present  and  future  possibili- 
ties were  very  much  belittled.  The  general  consensus  of  opinion 
at  that  time  of  those  who  pinned  their  faith  to  the  dirigible  was  that 
the  aeroplane  was  merely  a  scientific  toy — an  experiment  of  the 
laboratory  being  carried  out  on  a  larger  scale  and  nothing  more. 
There  seemed  but  little  question  that  the  airship  was  the  most  prac- 
tical means  of  navigating  the  air;  any  comparison  was  one-sided 
and  all  in  favor  of  the  dirigible,  for  up  to  that  time  aeroplane  per- 
formances had  been  confined  to  very  short  flights,  usually  with  the 
aviator  alone,  and  then  only  in  the  calmest  weather.  In  contrast 
with  this,  the  dirigible  could  remain  aloft  and  combat  winds  that 
were  then  considered  dangerous  to  the  aeroplane,  so  that  despite 
the  fact  that  the  dirigible  has  never  represented  anything  but  a  most 
precarious  and  costly  method  of  navigating  the  air,  it  was  the  most 
practical  means  of  doing  so  available  up  to  about  1906.  The  com- 
paratively few  years  that  have  intervened  have  totally  changed  its 
status.  Flights  such  as  those  made  by  Johnstone  and  Hoxsey  at 
the  International  Meet  in  the  fall  of  1910,  during  which  they  were 
driven  backward  40  and  30  miles,  respectively,  by  a  wind  exceeding 
50  miles  an  hour,  aft^r  which  both  alighted  safely,  demonstrate  con- 
clusively that  the  aeroplane  is  now  vastly  the  superior  of  the  dirigible 
as  far  as  keeping  to  the  air  in  stormy  weather  is  concerned.  Under 
the  same  conditions,  the  motors  of  the  most  powerful  dirigible  ever 
built  would  have  been  helpless;  an  attempt  to  land  would  have 
meant  inevitable  destruction  of  the  airship  and  probably  the  death 
of  some  of  its  crew,  and  yet,  as  the  ocean  was  right  at  hand  in  the  case 
in  question,  there  would  have  been  no  alternative  but  to  land  despite 
the  gale  that  was  blowing. 

Portability.  Where  it  is  impractical  for  strategical  reasons  to  fly 
from  the  point  at  which  aeroplanes  are  permanently  stationed,  they 
may  be  partly  dismantled  by  folding  the  wings,  may  be  placed  on 
a  specially  designed  automobile  as  shown  in  the  Bleriot  war  mono- 


Til 


8 


AVIATION  AND   ITS   FUTURE 


plane  Fig.  2,  and  be  transported  a  considerable  distance  in  less 
time  than  is  necessary  to  get  an  airship  out  of  its  shed,  thus  approach- 
ing an  enemy's  location  from  an  unexpected  direction.  In  the  same 
manner,  they  can  always  be  carried  along  as  a  regular  part  of  an 
army's  field  equipment,  and  may  be  sent  aloft  at  short  notice.  They 
may  also  be  carried  on  naval  vessels  in  the  same  capacity  and  undoubt- 
edly this  will  be  the  case  in  the  near  future,  as  the  result  of  the  highly 
successful  experiments  made  in  this  country.  At  a  considerable 
height,  well  within  the  range  of  the  aviator's  vision,  an  aeroplane  is 
not  alone  an  extremely  difficult  thing  to  hit,  but  likewise  a  very  diffi- 


Fig.  2.     Bleriot  Military  Monoplane,  Showing  Portability  Feature 

cult  thing  to  see  at  all  and  can  be  followed  only  by  close  concentra- 
tion on  the  part  of  the  observer.  The  dirigible,  on  the  other  hand, 
is  always  plainly  visible,  even  at  heights  that  would  render  observa- 
tions on  the  part  of  its  crew  of  very  little  value.  Unless  struck  in  a 
vital  part,  disabling  the  motor  or  killing  the  aviator,  a  chance  shell 
would  not  interfere  with  an  aeroplane's  flight,  but  a  single  rent  in  the 
envelope  of  a  dirigible  of  the  flexible  type  would  terminate  its  voy- 
age then  and  there,  the  Zeppelin  multi-cellular  type  with  its 
numerous  independent  gas  bags  being  free  from  this  disadvantage. 
But  despite  its  manifold  shortcomings,  the  various  Zeppelin 
disasters,  the  numerous  serious  mishaps  that  have  befallen  the 


712 


AVIATION   AND   ITS   FUTURE  9 

German  military  dirigible  Parseval,  and  the  several  misfortunes  of 
different  French  airships,  governments  will  probably  continue  to 
build  dirigibles.  The  French  and  German  military  departments, 
however,  having  had  a  wide  experience  in  this  field,  are  devoting  a 
great  deal  more  attention  to  the  aeroplane,  France  having  been  the 
first  to  officially  adopt  this  fourth  arm  as  a  part  of  its  military  serv- 
ice, and  now  having  an  aerial  fleet  far  outnumbering  that  of  any 
other  nation.  England,  too,  will  probably  question  carefully  further 
developments  along  this  line  in  view  of  her  recent  experience  with 
the  huge  British  naval  dirigible  Mayfly,  which,  although  completed 
late  in  1911  at  an  enormous  cost,  was  completely  wrecked  at  the 
first  attempt  to  take  it  out  of  the  shed.  Through  what  has  generally 
been  regarded  as  ultra-conservatism,  the  United  States  has  not  had 
to  pay  for  the  experience  which  European  governments  have  paid  so 
highly  for — its  one  small  dirigible  is  said  to  have  cost  but  $30,000, 
or  less  than  the  expense  of  fitting  up  one  of  the  large  French  or 
German  airships — and  there  appears  to  be  but  scant  prospect  that 
any  more  money  will  be  spent  in  this  direction  in  America. 

Recent  Developments  in  Dirigibles.  Types.  Despite  the 
destruction  of  the  various  Zeppelin  airships,  their  builder  has  never 
lost  faith  in  the  rigid  type  of  dirigible  he  has  evolved,  and  interest 
in  aerial  passenger  transportation  in  Germany  is  on  the  increase 
rather  than  otherwise.  The  Zeppelin  VI  made  34  trips,  but  bad 
weather  was  so  constant  that  she  was  able  to  sail  only  on  19  days  out 
of  the  total  of  25  that  the  ship  was  in  commission  before  being 
destroyed.  On  these  ^rips,  406  passengers  were  carried,  in  addition 
to  a  crew  consisting  of  a  captain,  two  pilots,  and  five  engineers,  or 
an  average  of  20  persons  per  trip.  The  trips  varied  from  50  to  125 
miles  each,  and  some  idea  of  the  financial  return  may  be  gained  from 
the  fact  that  during  the  short  time  it  was  in  operation,  the  ship 
brought  in  $19,000,  of  which  $11,215  was  profit.  So  promising  is 
the  financial  reward  accruing  from  the  operation  of  aerial  passenger 
lines  that  there  are  several  in  Germany,  and  if  press  reports  appear- 
ing during  the  winter  of  1911  have  a  basis  of  fact,  a  similar  enter- 
prise on  a  smaller  scale  should  be  established  during  1912  between 
Philadelphia,  New  York,  and  Atlantic  City,  it  being  reported  that 
airships  of  the  Parseval  type  had  been  acquired  for  the  purpose. 
The  Zeppelin  Airship  Construction  Company  has  been  incorpora- 


713 


10  AVIATION   AND   ITS   FUTURE 

ted  in  Germany  with  $3,000,000  capital  to  carry  forward  Count 
Zeppelin's  work,  and  an  immense  plant  has  been  established  at  Fried- 
richshafen  for  the  construction  of  the  huge  rigid  dirigibles.  One  of 
the  first  that  was  built  there  was  the  Deutschland  II,  which  went 
into  commission  in  the  fall  of  1910;  a  great  deal  was  expected  of 
her  during  the  following  year  when  she  was  to  be  stationed  at  Diissel- 
dorf,  first  for  making  excursion  trips  of  100  to  150  miles,  and  ulti- 
mately to  carry  on  a  regular  passenger  service  between  Diisseldorf 
and  Hamburg,  but  she  was  wrecked  after  a  comparatively  short 
time  in  commission  in  much  the  same  manner  as  most  of  her  prede- 
cessors. The  Schwaben  was  put  into  service  shortly  after  and  proved 
very  successful,  having  made  140  trips  during  1911,  carrying  a  great 
number  of  passengers,  her  immunity  from  accident  being  due  in 
large  part  to  the  improved  methods  of  handling  the  ship  in  docking. 
The  Deutschland  II  was  485  feet  long  by  46  feet  in  diameter,  the 
Schwaben  being  slightly  smaller.  Duralumin,  a  new  alloy  of  alumi- 
num of  greatly  increased  tensile  strength,  has  been  adopted  for  the 
frames,  increasing  the  passenger  capacity  to  26,  as  compared  with  20 
in  the  older  ships.  The  design  has  also  been  modified  by  allowing 
sufficient  space  between  the  outer  covering  of  weatherproof  cloth  and 
the  silk  gas  bags  to  permit  of  a  constant  draught  of  air  over  the  latter, 
thus  keeping  the  temperature  approximately  uniform  and  prevent- 
ing sudden  expansion  or  contraction  of  the  hydrogen. 

It  will  be  apparent  from  this  that  Germany  has  commercialized 
the  dirigible  on  a  large  scale — in  fact,  there  is  little  or  no  conception 
here  of  the  amount  of  money  that  is  being  expended  on  the  airship 
abroad,  as  may  be  noted  from  the  following  resume  of  some  of  the 
large  dirigibles  now  in  existence.* 

The  huge  French  airship  Clement-Bayard  II  and  the  English 
Morning  Post  were  largely  the  result  of  popular  rivalry  between  the 
two  nations  in  this  field.  The  latter  has  a  capacity  of  353,000  cubic 
feet  and,  with  the  exception  of  the  rigid  Zeppelins,  was  the  largest 
airship  ever  constructed,  up  to  the  time  of  its  building.  It  has  since 
been  surpassed  by  the  German  non-rigid  Krell  I,  a  giant  of  459,160 
cubic  feet  capacity,  The  experiences  of  military  service  have  evi- 


*"In  existence"  must  be  regarded  as  referring  only  to  the  time  at  which  it  was  written. 
It  only  takes  a  few  minutes  to  demolish  a  dirigible,  but  months  or  a  year  may  be  necessary 
to  rebuild  it. — Ed. 


714 


AYIATION   AND   ITS    FUTURE  11 

dently  shown  the  necessity  of  greatly  increasing  the  size  of  the  ves- 
sels, but  not  to  the  extent  that  obtains  with  the  passenger-carrying 
craft.  Thus  the  new  French  Captaine  Marechal,  named  after  the 
Republique's  unfortunate  commander,  displaces  254,304  cubic  feet, 
or  nearly  three  times  that  of  La  Republique,  while  the  new  Italian 
military  dirigible  has  a  displacement  of  282,560  cubic  feet. 

As  a  general  rule,  the  French  have  devoted  more  attention  to  the 
construction  of  airships  than  to  the  art  of  handling  them,  so  that 
during  last  year's  military  maneuvers,  some  of  their  dirigibles  had 
narrow  escapes.  With  the  exception  of  the  small  Zodiacs,  the  French 
military  airships  are  rarely  used  to  the  extent  that  one  would  expect. 
In  England,  airships  have  been  developed  by  the  army  on  a  small 
scale.  As  a  sea  power,  England  is  naturally  concerned  with  the 
development  of  the  dirigible  as  an  auxiliary  to  the  navy.  Big  though 
they  were  at  the  very  outset,  the  Zeppelins  have  grown  from  59,160 
to  706,400  cubic  feet  capacity.  The  British  naval  dirigible  begins 
at  the  latter  figure.  The  latest  passenger  airship  built  for  Belgium 
by  the  French  Astra  Company,  the  Mile  de  Bruxelles,  displaces 
about  282,560  cubic  feet.  On  the  other  hand,  the  most  advanced 
experimental  types,  the  German  Krell  I  and  the  British  Mayfly,  were 
designed  solely  for  military  purposes.  The  new  Belgian  ship,  how- 
ever, is  an  interesting  type.  The  single  large  propeller  of  the  classic 
La  France  of  30  years  ago  is  still  retained,  in  addition  to  which  there 
are  the  two  elevated  side  propellers,  driven  by  a  separate  motor,  as 
in  the  Clement-Bayard  design,  but  somewhat  smaller  in  size.  The 
result  is  that  the  shi^  remains  under  control  even  after  the  front 
propeller  is  stopped  in  landing.  The  Parseval  form  of  envelope, 
characterized  by  the  blunt,  ovoid  bow,  is  employed.  It  is  hardly  nec- 
essary to  discuss  the  comparative  merits  of  the  so-called  flexible, 
semi-rigid,  and  rigid  systems  of  construction  in  this  connection.  The 
very  largest  sizes  must,  of  necessity,  be  rigid.  For  the  smaller  air- 
ships, each  system  has  its  own  advantages  and  disadvantages. 
England  and  France  now  have  rigid  types,  as  well  as  Germany. 
France  is  the  home  of  the  dirigible,  but  the  French,  who  were  respon- 
sible for  its  invention,  have  not  developed  lighter-than-air  craft  as 
systematically  as  the  Germans. 

Refinement  of  Details.  The  tremendously  increased  size  of  the 
up-to-date  airship  has  tended  to  greater  refinement  of  detail.  Donkey 


715 


12  AVIATION   AND   ITS   FUTURE 

engines  are  becoming  a  common  feature  of  their  motor  equipment* 
the  Krell  I,  the  Akron,  Vaniman's  transatlantic  dirigible,  and  Bruck- 
er's  transatlantic  trade-wind  ship,  the  Suchard,  all  being  fitted  with 
them.  The  gas  bags  of  both  rigid  and  non-rigid  dirigibles  are  sub- 
divided into  compartments  like  a  ship,  this  construction  having  been 
first  introduced  in  the  Zeppelins.  Multiple  balloonets  are  also  being 
adopted  in  greater  number,  the  good  features  of  one  ship  being 
promptly  copied  in  another.  Thus,  the  English  Zeppelin  "Mayfly" 
adopted  the  propeller  mounting  of  the  Krell  I,  the  object  being  to 
avoid  long  transmissions.  In  shape,  it  also  approached  the  non- 
cylindrical  form,  the  Zeppelin,  however,  still  remaining  essentially 
cylindrical.  The  larger  the  ship,  the  more  elaborate  is  its  equip- 
ment. Wireless  telegraph  apparatus  is  now  carried  by  the  Zeppelin 
passenger  ships  as  well  as  by  the  military  dirigibles,  so  that  the 
navigator  may  constantly  keep  in  touch  with  meteorological  stations 
and  be  kept  informed  as  to  the  weather.  Valuable  experiments  have 
been  carried  out  by  the  Zeppelin  company  to  guard  its  airships  against 
atmospheric  electricity.  In  fact,  the  Zeppelin  company  profits  by 
its  experience  and  tries  to  prevent  the  same  accident  being  repeated. 
Thus,  the  new  Deutschland  had  an  increased  dynamic  lift,  an 
improvement  that  was  made  immediately  following  the  disaster  to 
its  predecessor.  As  a  result,  this  dirigible  rose  to  a  height  of  3,800 
feet  without  casting  over  any  ballast;  this  lift  later  proved  insuf- 
ficient and  the  Schwaben  was  further  improved.  Probably  the 
Zeppelin  type  would  be  still  better  if  it  had  a  continuous  car  like  the 
Akron,  containing  the  motors  and  crew,  in  place  of  two  cars  which 
are  really  a  legacy  of  the  old  spherical  balloon.  Adherence  to  type 
has  hampered  the  development  of  the  airship,  just  as  it  kept  back 
the  improvement  of  the  railway  car.  Just  as  early  railroad  coaches 
were  merely  enlarged  horse-drawn  coaches,  so  the  modern  dirigible,  in 
a  sense,  is  still  an  enlarged,  elongated,  spherical  balloon,  equipped  with 
a  motor.  Obviously,  an  airship  should  have  the  same  unbroken  lines 
below  as  above  to  insure  speed,  and  this  idea  has  been  carried  out 
by  Vaniman  in  the  Akron. 

Air  Pilots.  To  guide  one  of  these  huge  craft  through  atmos- 
pheric disturbances  of  more  or  less  violence  requires  considerable 
skill,  and  the  long  period  of  apprenticeship  necessary  in  the  con- 
struction and  piloting  of  a  dirigible — a  period  which  is  longer,  strange 


716 


AVIATION   AND   ITS   FUTURE  13 

as  It  may  seem,  than  in  the  case  of  the  aeroplane — accounts  for  the 
slow  development  of  the  types  with  which  we  are  familiar.  Although 
the  German  army  experiments  daily  in  the  air,  the  tactical  handling 
of  dirigibles  is  still  shrouded  in  mystery.  No  doubt,  there  are  defin- 
ite rules  to  be  followed,  but  what  they  may  be  can  only  be  surmised. 
Even  night  trips  are  said  to  be  frequent  with  the  German  military 
dirigibles. 

Major  von  Parseval  has  said  of  the  competent  air  captain:  "He 
must  know  exactly  the  speed  of  his  ship  and  of  its  maneuvering 
ability.  Above  all,  he  must  have  a  nice  sense  of  the  responsiveness 
to  the  vertical  steering  apparatus,  and  be  able  to  estimate  the  ship's 
carrying  capacity  with  considerable  accuracy." 

On  trips  from  Munich,  the  L.  P.  VI  covered  3,000  miles  and, 
with  frequent  small  injections  of  fresh  hydrogen,  has  remained 
inflated  for  twelve  weeks.  On  one  trip  she  combated  a  gale  of  34 
miles  an  hour,  a  speed  hardly  exceeded  by  the  vessel  at  its  best. 
The  captain  made  considerable  headway  by  tacking  into  lulls,  keep- 
ing the  harbor  well  to  leeward,  ready  to  return  and  land  at  a  moment's 
notice.  This  was  airmanship  of  a  high  order.  This  ship  has  had 
the  unique  experience — for  air  craft — of  being  chartered  for  a  special 
trip  to  Kiel,  which  it  is  proposed  to  make  as  important  an  air- 
ship station  as  it  now  is  a  naval  base.  And  the  ship  has  also 
added  to  its  revenues  as  a  passenger  carrier  by  serving  as  a  back- 
ground at  night  upon  which  to  throw  stereopticon  advertising. 

Air  Harbors.  With  the  aeroplane,  the  question  of  housing  is 
a  simple  matter,  Fig(  3,  but  as  each  new  military  airship  has  become 
larger,  the  problem  of  sheltering  it  has  become  more  difficult.  Fig. 
4  gives  some  idea  of  the  size  of  the  harbor  for  a  modern  dirigible. 
It  has  resolved  itself  into  a  question  of  establishing  a  number  of 
permanent  harbors  in  Germany.  These  are  on  a  truly  colossal 
scale,  those  at  Konigsberg  and  Thorn,  fortresses  on  the  German 
frontier,  have  been  designed  to  house  ships  half  as  large  again 
as  the  biggest  vessels  now  in  service.  For  craft  so  huge,  portable 
sheds  are  out  of  the  question.  Permanent  harbors  must  be  con- 
structed, which  will  serve  as  bases  for  craft  having  a  wide  radius 
of  action.  The  new  Zeppelin  air  harbors  are  on  an  elaborate  scale. 
To  the  stations  already  established  at  Diisseldorf  and  Baden-Baden, 
a  number  of  others  are  now  being  added,  and  smaller  cities  that  can 


717 


14 


AVIATION  AND  ITS  FUTURE 


not  afford  to  provide  great  harbors  with  sheds  are  establishing  landing 
places  with  moorings,  and  aerial  beacons  will  shortly  become  com- 


MACH1HE  A  VOLER    • 
LOUIS     PAULHAH 


Fig.  3.     An  Aeroplane  Hangar 


Fig.  4.     Immense  Harbor  Necessary  for  Vaniman's  Transatlantic  Dirigible  "Akron" 

mon,  judging  from  the  success  of  those  in  use  at  Spandau  and  Mun- 
ich.    Dirigibles  are  started  on  their  journeys  and  docked  by  large 


718 


AVIATION  AND   ITS   FUTURE  15 

forces  of  trained  men,  but  even  long  practice  has  not  enabled  them 
to  handle  such  huge  air  craft  as  the  Krell  I  and  the  Schwaben,  with 
ease.  The  docking  of  a  big  dirigible  is  a  ticklish  operation  at  best 
and  is  made  dangerous  by  a  cross-wind,  only  the  new  system  of 
anchoring  devised  for  the  Schwaben  having  prevented  damage  to 
that  ship.  To  cut  down  the  expense  necessarily  entailed  in  main- 
taining such  a  large  force,  the  Krell  I  is  docked  partly  with  the  aid 
of  electric  winches,  and  this  is  something  that  will  probably  undergo 
considerable  development. 

Just  now,  inventive  ingenuity  is  concentrated  on  the  airship 
itself,  but  the  time  will  soon  be  ripe  for  a  consideration  of  the  prob- 
lem of  handling  the  ship  by  machinery  entirely.  Of  these  prob- 
lems, probably  the  most  difficult  is  that  of  anchoring  an  airship  in 
a  high  wind — in  the  Krell  I,  it  is  solved  by  employing  a  multiple 
anchor  cable  which  is  led  to  the  nose  of  the  ship  and  there  divided. 
The  24  single  ropes  into  which  it  separates  are  fastened  all  round  the 
envelope,  -where  the  diameter  is  not  less  than  20  feet. 

Improvements  of  Design.  Where  the  construction  itself  is  con- 
cerned, all  other  difficulties  of  building  large  airships  are  summed  up 
in  the  well-known  fact  that,  as  a  structure  increases  in  size,  the  mar- 
gin of  safety  does  not  increase  in  proportion.  In  other  words,  to 
build  a  successful  airship  300  feet  long  on  exactly  the  same  lines  as 
one  150  feet  long,  it  would  not  be  correct,  from  an  engineering  view- 
point, to  scale  up  the  parts  of  the  smaller  craft  to  the  proportionate 
size  of  the  larger.  The  big  Morning  Post,  which  is  a  Lebaudy  of 
353,200  cubic  feet  displacement,  is  simply  a  Lebaudy  of  105,960  cubic 
feet,  enlarged  line  for  line.  There  is  but  a  single  car,  very  close  to 
the  envelope  at  that.  But  it  can  not  be  denied  that  the  crossing  of 
the  English  Channel  at  its  widest  part  and  its  journey  from  Moissons 
to  Aldershot  in  five  hours  and  in  a  strong  wind,  shows  that  size  must 
be  very  greatly  increased  before  the  structural  danger  point  is 
reached.  The  Krell  I  seems  to  embody  the  opposite  principle, 
namely,  that  an  .increase  of  size  beyond  105,000  cubic  feet  involves 
the  very  best  efforts  of  the  engineer  to  increase  the  factor  of  safety 
proportionately.  There  are  not  simply  two  cars  instead  of  one, 
but  three,  so  suspended  that  the  pull  on  the  gas  bag  is  all  in  a  ver- 
tical direction,  differing  radically  from  the  oblique  suspension  and 
pull  in  the  Morning  Post.  Hence,  in  the  Krell  I  a  minimum  strain 


719 


16  AVIATION   AND   ITS   FUTURE 

is  imposed  upon  the  envelope.  It  is  true  that  the  latter  ship  is 
uncommonly  slender  in  spite  of  the  absence  of  the  stiffening  frame 
on  which  the  Morning  Post  essentially  relies.  Whatever  may  be 
the  shape  of  envelope,  the  material  is  subjected  to  tensile  stresses 
only. 

The  new  German  military  dirigible  M.  IV  is  provided  with  a 
very  substantial  stiffening  frame,  so  designed  that  the  load  is  divided 
in  half.  Its  engine  power  has  also  been  very  substantially  increased. 
Zeppelin's  Deutschland  II  was  considerably  lightened  without  any 
fundamental  change  in  plan  or  material,  the  girders  being  redesigned 
more  effectively.  The  British  dirigible  Mayfly,  of  very  similar  type, 
was  built  of  duralumin,  the  result  being  that  its  engine  power  was 
higher,  and  that  its  radius  of  action  for  the  same  displacement 
should  have  been  greater.  Both  the  Deutschland  and  the  Mayfly 
were  nearly  identical  in  design  with  the  first  Zeppelins  of  459,000 
cubic  feet  only.  In  neither  case  was  it  considered  necessary  to  in- 
crease the  margin  of  structural  safety  with  the  size,  and  both  were 
wrecked  after  a  short  period,  the  British  ship  before  it  had  seen 
any  service. 

The  foregoing  will  suffice  to  give  some  idea  of  the  exceptional 
activity  that  characterizes  the  present  development  of  the  dirigible 
abroad,  as  compared  with  the  utter  apathy  with  which  it  is  viewed 
in  this  country.  Americans  who  have  not  gone  abroad  have  never 
had  an  opportunity  of  seeing  a  modern  dirigible  as  exemplified  by 
the  German  and  British  types  referred  to  above,  but  if  the  Ameri- 
can service  mentioned  should  prove  successful,  those  in  the  East 
may  see  similar  dirigible  airships  in  passenger  service. 

REWARDS  OF  AVIATION 

Human  nature  is  so  constituted  that  men  may  be  found  to 
attempt  anything  if  the  financial  reward  be  sufficiently  large;  and 
it  is  this  spirit  that  makes  the  impossible  of  today  the  achievement 
of  a  week  or  so  hence,  as  is  strikingly  illustrated  by  the  rapidity  with 
which  records  were  surpassed  during  the  past  two  years.  In  review- 
ing the  latter,  due  credit  must  be  accorded  the  powerful  incentive 
to  extraordinary  effort  represented  by  the  cash  prizes  offered  both 
in  this  country  and  abroad.  Despite  the  large  sums  given,  the  break- 
ing of  a  record  has  immediately  brought  forth  offers  of  still  larger 


720 


AVIATION  AND   ITS   FUTURE  17 

amounts.  The  achievements  of  the  past  few  years  have  been 
paid  for  at  a  cost  exceeding  a  million  dollars  in  prize  money 
alone,  and  it  goes  without  saying  that  this  has  spurred  aviators 
on  to  efforts  that  probably  would  not  have  been  made  otherwise 
until  some  time  later.  The  following  are  some  of  the  prizes  won 
during  1910  and  1911,  as  well  as  a  number  still  standing  or  to  be 
offered  during  1912. 

Prizes  for  Flights.  The  International  Trophy,  Fig.  5,  was  offered 
by  James  Gordon  Bennet  and  was  first  competed  for  in  connection 
with  the  International  Aviation  Meet,  at  Rheims,  France,  where  it 
was  won  by  Glenn  H.  Curtiss  in  a  Curtiss  biplane  in  August,  1909. 
In  the  following  year  it  was  competed  for  at  the  International  Meet 
held  at  Belmont  Park,  New  York,  in  October,  1910.  In  this  event 
Leblanc  broke  all  records  for  distances  up  to  95  kilometers,  but 
when  he  had  the  victory  in  sight  with  several  minutes  lead,  the 
gasoline  supply  failed  and  his  machine  dropped  on  a  telephone  pole. 
The  machine  was  a  100-horse-power  Bleriot,  and  was  completely 
wrecked,  although  Leblanc  escaped  without  injury.  This  allowed 
Claude  Grahame  White  to  win  in  a  50-horse-power  machine  of  the 
same  type. 

The  prize  is  offered  for  the  fastest  time  over  a  three  kilometer 
circular  course  and  is  to  be  competed  for  in  the  country  of  the  pre- 
vious winner.  The  trophy  is  to  be  awarded  permanently  after  hav- 
ing been  won  three  times  consecutively  by  an  aviator  of  the  same 
nationality.  As  Grahame-White  is  an  Englishman,  the  third  com- 
petition was  accordingly  held  in  Great  Britain  in  July,  1911,  the 
trophy  being  won  by  an  American  for  the  second  time.  This  was 
Weyman,  who  drove  a  Nieuport  monoplane  equipped  with  a  100- 
horse-power  Gnome  motor.  The  distance  was  originally  100  kilo- 
meters, but  as  the  staying  capacity  of  the  aeroplane  developed  so 
rapidly,  this  was  held  to  for  only  two  years,  the  distance  in  1911 
being  150  kilometers. 

The  first  substantial  prize  to  be  won  in  this  country  was  that 
of  $10,000  awarded  by  the  New  York  World  to  Glenn  H.  Curtiss  for 
his  flight,  on  May  29,  1910,  from  Albany  to  New  York,  a  distance 
of  148  miles.  This  immediately  led  to  the  offer  of  $25,000  by 
the  New  York  Times  and  Chicago  Evening  Post  to  the  winner  of  a 
race  between  the  two  cities,  the  only  conditions  being  that  there  must 


721 


COUPE  WTEBNATIOJiALE  DEVIATION, 


Fig.  5.     Gordon-Bennett  International  Trophy 


723 


AVIATION   AND   ITS   FUTURE  19 

be  at  least  three  competitors  and  that  the  total  time  for  the  trip 
must  not  exceed  168  hours.  This  amount  was  increased  by  the  offer 
of  the  Pennsylvania  Aero  Club  of  $1,0,00  for  a  week's  exhibition  of 
the  winning  machine,  with  a  further  increase  of  $1,000  offered  by 
Clifford  B.  Harmon  to  the  first  aviator  to  keep  the  air  for  500  miles 
consecutively  in  that  race,  bringing  the  total  winning  possible  in 
this  event  to  $27,000.  This  was  exceeded  by  the  offer  of  $30,000  by 
the  New  York  World  and  the  St.  Louis  Post-Dispatch  for  a  flight 
between  St.  Louis  and  New  York,  and  the  $50,000  prize  put  up  by 
William  R.  Hearst  for  the  first  successful  flight  from  the  Altantic 
to  the  Pacific  in  a  dirigible,  the  latter  having  the  great  disadvantage 
that  the  cost  of  a  machine  capable  of  making  the  trip  would  exceed 
by  several  times  the  amount  of  the  reward,  whereas  the  cost  of  an 
aeroplane  is  but  a  fraction  of  some  of  the  larger  prizes.  It  was  later 
extended  to  cover  an  aeroplane  flight  as  well. 

Two  attempts  were  made  to  win  the  Hearst  $50,000  prize  during 
the  fall  of  1911,  but  neither  succeeded  in  complying  with  the  con- 
ditions, which  called  for  the  crossing  of  the  continent  in  30  days. 
C.  P.  Rodgers  in  a  Model  "B"  Wright  machine  made  the  journey  from 
New  York  to  Pasadena  by  way  of  Chicago,  Kansas  City,  Dallas,  and 
San  Antonio  in  59  days,  the  distance  being  3,390  miles.  Although 
the  airline  distance  is  only  2,540  miles,  it  will  be  some  time  before 
an  aviator  will  feel  sure  enough  of  himself  to  follow  an  airline  route. 
Rodgers  was  greatly  delayed  by  numerous  mishaps  and  also  by  stop- 
ping for  exhibition  purposes.  He  was  convoyed  by  a  special  railroad 
train,  one  car  of  whfch  was  fitted  as  a  machine  shop.  On  attempting 
after  a  rest  at  Pasadena  to  make  the  remaining  25  miles  to  the  coast 
at  Long  Beach,  his  aeroplane  fell  and  the  plucky  aviator  nearly  lost 
his  life.  Notwithstanding  his  machine  was  almost  a  total  wreck,  it 
was  again  repaired  and  Rodgers  finished  his  journey  about  a  month 
later,  thus  completing  what  must  be  considered  a  very  noteworthy 
flight.*  Fowler,  who  started  from  the  west  coast,  was  even  more 
unfortunate  and  had  to  give  up  the  attempt  to  cross  the  mountains 
after  several  trials,  taking  the  southerly  route  instead.  His  ill-luck 
still  pursued  him,  so  that  after  more  than  three  months'  work  he  had 


*  After  completing  his  coast-to-coast  journey,  Rodgers  had  been  making  almost  daily 
exhibition  flights  over  the  water  at  Long  Beach,  California.  On  April  3,  1912,  he  mis- 
judged his  proximity  to  the  surf  at  the  end  of  a  "volplane"  from  a  height  of  200  feet, 
dashed  into  the  water,  and  was  almost  instantly  killed. 


723 


20 


AVIATION  AND   ITS   FUTURE 


succeeded  in  getting  no  farther  than  New  Orleans.    He  subsequently 
completed  the  trip,  landing  at  Jacksonville,  Florida. 

That  these  prizes,  on  the  one  hand,  are  not  unusually  large, 
nor,  on  the  other,  merely  prizes  that  may  be  won  in  the  indefinite 


Fig.  6.     Michelin  Trophy  for  Longest  Continuous  Flight 

future,  is  amply  evidenced  by  some  of  the  winnings  of  foreign  aviators 
in  the  past.  The  most  prominent  of  the  latter  was  naturally  the 
$50,000  prize  won  by  Paulhan  in  his  flight  from  Manchester  to 
London,  April  28,  1910,  while  Wynmalen,  the  Belgian  aviator,  won 


724 


AVIATION   AND   ITS   FUTURE 


21 


$20,000  on  October  16,  1910,  by  his  flight  from  Paris  to  Brussels 
and  return  in  less  than  36  hours.  The  Michelin  prize  of  $20,000 
together  with  the  Michelin  trophy,  Fig.  6,  were  gained  by  Tabuteau 
for  his  flight  of  365  miles,  Fig.  7,  the  longest  continuous  flight  made 
during  1910  but  which  was  surpassed  by  a  substantial  margin  in  1911. 
Fig.  8  shows  the  enormous  gasoline  tank  necessary  for  this  perform- 
ance, while  Fig.  9  shows  the  provisions  for  protecting  the  operator. 
It  was  in  attempting  to  win  the  Michelin  prize  that  Moissant  lost 
his  life  at  New  Orleans,  on  December  31,  1910.  Another  Michelin 
prize  of  $20,000  is  for  a  flight  from  Paris  to  the  Puy  de  Dome  with  a 


Fig.  7.     Tabuteau,  Winner  of  Michelin  Prize  in  1910,  in  Flight 

passenger.  This  is  a  mountain  4,800  feet  high  and  about  217  miles 
in  an  airline  from  the  French  capital,  the  conditions  being  that  the 
aviator  must  circle  the  cathedral  spire  at  Clermont-Ferrand  on  the 
way,  and  that  the  trip  must  not  consume  more  than  six  hours. 
Several  attempts  to  win  this  prize  have  been  made  without  success. 
Weyman  flew  within  13  miles  of  the  goal  on  September  7,  but  lost 
his  bearings  and  was  compelled  to  descend  owing  to  fog  and  rain. 
Morane,  who  was  to  have  competed  at  the  International  Meet  near 
New  York,  made  an  attempt  on  October  22,  but  was  seriously  injured 
through  the  fall  of  his  100-horse-power  Bleriot  soon  after  leaving 
Paris.  It  was  finally  won  in  an  M.  Farman  biplane  in  the  summer 


725 


22 


AVIATION   AND   ITS   FUTURE 


of  1911.  Still  another  prize  and  the  British  Michelin  trophy,  Fig.  10, 
were  won  by  Cody  in  his  biplane,  when  he  covered  194.56  miles  in  4 
hours  and  50  minutes. 

Prizes  of  similar  amounts  are  not  lacking  in  this  country ;  among 
them  may  be  mentioned  one  of  $20,000  offered  by  the  Aero  Club 
of  Washington  to  the  Wright  Brothers  for  a  flight  from  New  York 


Fig.  8.     Close  View  of  Tabuteau  Showing  Immense  Gasoline  Supply  Tank 

to  Washington,  if  they  will  enter  one  of  their  machines  against  a 
Curtiss,  while  a  prize  of  $10,000  is  offered  by  James  H.  Moore,  of 
Rochester,  New  York,  for  a  flight  from  that  city  to  Detroit,  Michigan. 
The  conditions  in  this  case  are  to  be  left  to  the  decision  of  a  com- 
mittee of  aviators.  More  than  one  attempt  has  already  been  made 
to  win  this  by  local  talent,  but  with  scant  success.  Numerous  prizes 


726 


AVIATION   AND   ITS   FUTURE 


23 


have  also  been  offered  and  won  for  altitude  flights,  Brookins  placing 
$5,000  to  his  credit  by  his  record-breaking  ascent  at  Atlantic  City 
on  July  9,  1910. 

Naturally,  the  largest  aggregate  amounts  are  those  offered  at 
prominent  meets,  the  winnings  of  the  aviators  at  the  International 


Fig. 


View   of    Operator's    Seat   in    Aeroplane    Designed  for  Altitude  Flights,  Showing 
Means  of  Protection  from  Extreme  Cold 


Meet  at  Belmont  Park  in  October,  1910,  having  reached  a  total  of 
approximately  $200,000,  the  participants  in  this  case  also  having 
been  awarded  a  share  of  the  gate  receipts.  Before  the  opening  of 
the  meet,  $50,000  was  appropriated  for  cash  prizes,  as  follows: 
three  prizes  of  $4,500  each  for  speed,  altitude,  and  distance;  an 
altitude  record  prize  of  $5,000  or  $10,000  for  the  aviator  first  to  reach 


727 


24 


AVIATION  AND   ITS   FUTURE 


10,000  feet;  in  addition  there  were  what  might  be  termed  con- 
solation prizes  amounting  to  $250  for  each  hour  the  aviators 
were  in  the  air  during  the  duration,  speed,  and  altitude  tests.  (See 
Fig.  11.)  These  were  supplemented  by  correspondingly  large  amounts 


Fig.  10.      Michelin  British  Trophy  for  Distance  Flight 

for  cross-country  flights,  as  well  as  prizes  for  passenger  carrying, 
relay  messenger  service,  slow  flying,  quick  starting,  and  other  feats, 
besides  which  there  was  a  prize  of  $10,000  for  the  winner  of  a  race 
from  Belmont  Park  round  the  Statue  of  Liberty  and  back. 

At  smaller  meets,  the  amounts  offered  have  been  proportionately 


7538 


m.  W. 


729 


26  AVIATION   AND   ITS   FUTURE 

large,  the  Boston  Globe  offering  $10,000  for  the  fastest  trip  over  the 
water  from  the  aviation  field  at  Atlantic  City  round  the  Boston  Light 
and  back  on  the  occasion  of  the  Harvard  Meet  near  Boston,  in  Sep- 
tember, 1910.  In  addition  to  this,  first,  second,  and  third  prizes  of 
$3,000,  $2,000,  and  $1,000  were  offered  in  the  speed  and  altitude 
events,  and  $2,000  and  $1,000  in  the  duration  and  distance  compe- 
tition, the  making  of  a  world's  record,  in  either  case,  adding  $1,000 
to  the  amount.  Other  prizes  were  $1,000  and  $500  for  the  slowest 
lap  of  the  course,  with  smaller  amounts  for  the  quickest  start,  accu- 
racy, and  the  like,  the  total  offered  aggregating  $41,000.  At  the 
Baltimore  Meet,  in  November,  1910,  there  was  one  prize  of  $10,000, 
two  of  $5,000  each,  three  of  $3,500  each,  one  of  $1,500,  and  so  on 
down,  totalling  $32,700. 

The  Los  Angeles  Meet,  in  January,  1911,  was  the  first  to  include 
prizes  for  dirigibles.  In  addition  to  one  of  $10,000,  one  of  $7,500, 
and  four  of  $5,000  each,  for  aeroplanes,  a  prize  of  $10,000  was  offered 
for  a  flight  by  dirigible  from  Los  Angeles  to  San  Francisco,  and  another 
of  $5,000  for  a  non-stop  flight  by  a  dirigible  carrying  more  than  two 
passengers  from  Los  Angeles  to  San  Diego  and  back.  The  distances 
are  450  and  150  miles,  respectively.  A  $10,000  prize  was  also  offered 
for  a  trip  to  the  Atlantic  Coast  without  landing,  and  $5,000  for  the 
first  balloon  to  land  east  of  the  Mississippi  without  having  come  to 
earth  en  route,  with  a  further  balloon  prize  of  $2,500  for  breaking 
Count  de  la  Vaulx's  record  of  1,193  miles  and  $2,500  more  for  the 
first  balloon  to  land  within  five  miles  of  Sari  Francisco.  That  the 
coast-to-coast  balloon  trip  is  not  quite  as  chimerical  as  may  appear 
at  first  sight  from  the  mere  offer  of  a  prize,  is  evident  from  the  fact 
that  P.  C.  Thompson  has  offered  $10,000  to  Charles  J.  Glidden, 
the  well-known  balloonist,  to  finance  a  trip  of  this  kind,  and  the 
offer  has  been  accepted.  A  trophy  worth  $1,000  is  offered  for  its 
successful  completion,  and  no  conditions  are  imposed  other  than 
that  the  start  shall  be  made  at  some  point  on  the  Pacific  and  that 
the  balloon  shall  land  not  less  than  50  miles  from  the  Atlantic  Coast. 
H.  H.- Clayton,  who  acted  as  aid  in  the  Pommern  which  won  the 
International  Balloon  Race  in  1908,  will  probably  be  the  pilot. 

As  the  intention  is  merely  to  chronicle  the  extremely  strong 
incentive  that  is  being  offered  in  the  form  of  substantial  financial 
reward  for  record-breaking  performances,  no  attempt  has  been  made 


730 


AVIATION   AND   ITS   FUTURE  27 

to  detail  a  complete  list  of  the  prizes  either  won  or  offered,  there 
being  many  of  the  latter  in  addition  to  those  already  mentioned,  such 
as  the  prize  of  $5,000,  for  an  aeroplane  flight  over  the  90  miles  of 
the  Caribbean  Sea  separating  Key  West  from  Havana.  This  was 
awarded  to  McCurdy,  one  of  the  Curtiss  aviators,  although  his 
motor  broke  down  when  he  was  within  a  few  miles  of  Havana, 
having  flown  87  miles. 

Prizes  for  Improvements.  No  mention  of  the  reward  phase  of 
aviation  that  has  done  so  much  to  foster  interest  and  bring  about 
such  startling  achievements  would  be  complete  without  at  least  a 
reference  to  prizes  offered  for  improvements  in  construction,  as  the 
latter  are,  in  reality,  of  more  importance  than  achievements  which 
merely  illustrate  what  the  present  machines  are  capable  of  in  the 
hands  of  skilled  and  daring  aviators.  The  largest  of  these  was 
granted  to  Edouard  Nieuport  as  the  winner  of  the  French  military 
competition  for  army  aeroplanes;  the  bonus  and  value  of  the  order 
for  machines  placed  reached  a  total  of  $156,900;  the  second,  Breguet, 
received  $83,000;  and  the  third,  Deperdussin,  $59,000. 

In  America,  Edwin  Gould  has  offered  a  prize  of  $15,000  for 
"the  most  perfect  and  practicable  heavier-than-air  flying  machine, 
designed  and  demonstrated  in  this  country,  and  equipped  with  two 
or  more  complete  power  plants  (separate  motors  and  propellers)  so 
connected  that  any  power  plant  may  be  operated  independently, 
or  that  they  may  be  used  together."  During  the  two  years  that 
this  prize  has  been  open,  only  one  or  two  attempts  have  been  made 
to  win  it.  One  of  these  was  the  Queen  biplane,  built  near  New  York, 
which  came  to  grief  at  the  Nassau  Meet,  in  September,  1911,  after 
a  short  flight.  The  Short  biplane,  described  under  "Special  Types," 
appears  to  be  the  first  successful  machine  of  the  kind,  though  Sommer 
made  a  series  of  short  flights  on  a  machine  fitted  with  two  motors 
in  the  latter  part  of  1910.  As  both  of  these  are  foreign  machines, 
however,  they  would  not  be  eligible. 

Cost  of  Equipment  and  Maintenance.  While  the  rewards  offered 
are  unusually  large  and  the  winnings  of  some  aviators  have  amounted 
to  a  small  fortune  in  the  course  of  little  more  than  a  year,  the  expendi- 
tures for  machines  and  repairs  are  on  a  proportionately  elevated 
scale.  Following  are  some  of  the  prices  of  the  foreign  machines 
exhibited  at  the  Olympia  show  in  London,  in  the  latter  part  of  1910. 


731 


28  AVIATION   AND   ITS   FUTURE 

Wright  biplane  with  Wright  motor  (English  manufacture)  $5,839; 
Farman  biplane  with  Green  motor  $4,428;  and  with  Gnome  revolv- 
ing motor  15,450;  Voisin  biplane  with  E.  N.  V.  motor  $3,796; 
Antoinette  monoplane  with  Antoinette  eight-cylinder,  V-motor 
$4,866;  Bleriot  "Cross-Channel"  monoplane  $2,336;  Santos-Dumont 
monoplane  $1,460.  In  this  country,  the  Wright  machines  list  at 
$5,000  for  the  standard  type  and  $7,500  for  the  racer  with  an  eight- 
cylinder,  60-horse-power  motor,  and  a  glance  over  the  prices  of  the 
machines  exhibited  at  the  Boston  and  New  York  shows  during  1910 
make  it  apparent  that  an  investment  of  at  least  $4,000  to  $5,000  is 
required  in  the  purchase  of  a  machine  of  any  reputation.  An  Ameri- 
can-made Voisin  shown  at  Boston,  listed  $3,450;  while  an  American 
Blerioplane  was  $3,750,  which  included  instruction  in  its  operation. 
As  is  the  case  with  automobiles,  however,  machines  may  be  had  all 
the  way  from  $1,000  up,  with  no  limit  on  the  latter. 

In  addition  to  the  expense  for  machines,  of  which  every  promi- 
nent aviator  owns  several  representing  an  investment  of  $25,000 
or  more,  there  is  the  cost  of  maintenance,  viz,  transportation 
charges  for  machines,  and  expenses  for  mechanics,  fuel,  oil,  and 
repairs.  Of  these  charges,  the  last  is  by  far  the  most  serious;  trans- 
portation charges  are  high,  as  are  also  the  expenses  and  wages  of  the 
mechanics;  fuel  and  oil  do  not  cut  much  of  a  figure,  but  the  cost  of 
repairs  may  exceed  them  all.  Just  a  slight  swerve  in  alighting,  a  gust 
of  wind  gets  under  the  upraised  wing  tip  and  the  other  strikes  the 
ground;  the  complete  wing  structure  on  that  side  is  demolished — dam- 
age $250.  Or  again  a  propeller  strikes  an  obstruction  when  the  motor 
is  started  and  cracks  a  blade — that  means  replacement  at  a  cost  of 
$50  to  $85.  Slight  damage  to  the  motor  which  puts  it  out  of  com- 
mission for  a  day  or  two  may  occasion  the  purchase  of  another  to 
take  its  place — expense,  anything  from  $500  up  to  $2,000;  so  that 
expenditures  as  well  as  winnings  run  up  into  many  ciphers. 

AVIATION   RECORDS 

Regardless  of  how  great  the  achievements  of  the  future  may  be, 
the  record  of  man's  flights  in  heavier-than-air  machines  during  the 
first  few  years  of  his  conquest  will  go  down  into  history  as  repre- 
senting an  advance  wholly  unparalleled  in  any  other  field  of  endeavor 
in  the  same  period.  To  have  progressed  from  a  flight  lasting  twelve 


733 


AVIATION   AND   ITS   FUTURE  29 

seconds,  during  which  the  machine  was  not  really  under  control,  to 
flights  limited  in  distance  or  altitude  only  by  the  endurance  of  the 
aviator  or  the  amount  of  fuel  carried,  in  little  more  than  seven  years, 
is  certainly  a  record  of  performance  unapproached. 

Early  Records.  On  the  occasion  of  their  first  and  second  trials 
with  the  power-driven  machine  at  Kitty  Hawk,  North  Carolina,  on 
December  17,  1903,  the  Wright  Brothers  made  a  flight  of  12  seconds 
in  a  27-mile  wind.  On  the  fourth  trial,  a  flight  lasting  for  59 
seconds  and  covering  a  distance  of  852  feet  was  made  the  same 
day  in  a  20-mile  wind  and  was  the  first  actual  flight  by  man  in  an 
aeroplane,  demonstrating  that  the  aviator  had  control  of  the  machine. 
In  August,  1904,  at  Dayton,  Ohio,  a  flight  of  1  minute  duration 
was  made,  while  on  November  9,  of  the  same  year,  a  flight  of  3 
miles,  lasting  for  5  minutes  4  seconds,  was  made  with  the  second 
power-driven  machine  ever  built.  During  1904,  the  Wright  Brothers 
made  105  flights  in  all.  In  1905  they  made  49  flights,  the  performance 
of  October  5,  1905,  being  longer  than  all  of  those  preceding  it  put 
together.  The  time  of  this  flight  was  38  minutes  3  seconds,  covering 
241  miles,  which  was  the  world's  record  for  some  time  thereafter. 
This  flight  followed  one  of  11 J  miles  in  18  minutes  9  seconds,  on 
September  26,  1905.  No  flights  were  made  during  1906  and  1907. 

A  number  of  short  practice  flights  were  made  at  Kitty  Hawk, 
North  Carolina,  in  the  spring  of  1908,  and  on  October  18,  1908,  at 
Le  Mans,  France,  a  flight  of  1  hour  54  minutes  53  f  seconds  was 
made,  covering  a  distance  of  62  miles,  and  on  December  31,  1908, 
77  miles  were  covereo^  in  a  single  flight  in  2  hours  20  minutes  23t 
seconds.  No  less  than  100  flights  were  made  at  Le  Mans,  France, 
during  which  36  people  were  taken  up  as  passengers.  All  of  these 
flights  were  made  by  Wilbur  Wright,  who  was  accordingly  the  first 
man  to  remain  in  the  air  for  2  hours. 

Orville  Wright  made  the  first  flight  in  a  power-driven  machine 
at  Kitty  Hawk,  North  Carolina,  a  mere  glide  of  12  seconds,  and 
not  to  be  compared  for  length  or  duration  with  glides  previously 
made  in  planes  without  motors.  As  already  noted,  Wilbur  Wright's 
first  attempt  was  no  better.  On  September  15,  1904,  at  Dayton, 
Orville  Wright  made  the  first  turn  in  an  aeroplane  and  five  days  later 
accomplished  the  first  complete  circular  flight  ever  made.  On  Sep- 
tember 9,  1908,  at  Fort  Myer,  Virginia,  he  flew  at  an  altitude  of 


733 


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734 


AVIATION   AND   ITS   FUTURE  31 

150  feet,  making  a  world's  record,  while  three  days  later  he  flew  for 
1  hour  14  minutes  24  seconds,  covering  50  miles  at  an  altitude  of 
250  feet,  again  establishing  a  record  for  altitude. 

Records  for  1909  and  1910.  By  the  beginning  of  1910,  2-hour 
flights  had  become  so  common  and  so  many  were  made  during  that 
year  that  it  would  take  a  volume  to  record  them;  the  most  notable, 
however,  are  given  in  Table  I. 

Records  for  1911.  Flights  became  so  numerous  during  1911 
that  it  would  be  out  of  the  question  to  attempt  to  give  more  than 
passing  mention  to  some  of  the  most  prominent.  The  number  of 
licensed  pilots  in  America  increased  "from  26  in  1910  to  81  in  1911, 
while  it  is  conservatively  estimated  that  there  are  not  less  than 
2,000  flyers  in  France,  and  that,  during  1911,  they  made  15,000 
flights,  none  of  less  than  half  an  hour,  covering  a  total  of  350,000 
miles. 

Every  world's  record  which  1910  had  placed  so  far  in  advance  of 
anything  previously  accomplished  was  left  far  behind.  Garros 
mounted  13,947  feet;  Beachey  volplaned  more  than  12,000  feet; 
Fourney  flew  for  11  hours  without  stopping;  Gobe  exceeded  the 
distance  record  by  12  miles  in  three  hours  less  time,  and  without  a 
stop;  Helen,  two  weeks  after  becoming  a  pilot,  flew  750  miles  in 
14  hours,  including  six  stops  for  fuel — in  fact,  only  four  days  after 
receiving  his  certificate  he  flew  665  miles  in  12  hours  and  40  minutes 
with  three  stops;  Nieuport  and  Vedrines  made  a  speed  of  93  miles 
an  hour;  Frier  flew  from  Paris  to  London,  223  miles,  without  a  stop; 
Rodgers  flew  across  the  American  continent  by  easy  stages,  a  dis- 
tance of  2,567  miles;  from  New  York  to  San  Francisco,  while  Fowler 
made  half  the  distance  in  the  opposite  direction;  and  Atwood  flew 
from  St.  Louis  to  New  York,  1,155  miles,  and  immediately  afterward 
made  the  flight  from  Boston  to  Washington,  460  miles.  Between 
May  1  and  October  1,  Renaux  was  credited  with  6,830  kilometers 
(4,098  miles),  made  in  trips  of  100  kilometers  each,  while  Beaumont 
covered  nearly  3,000  miles  in  the  three  great  European  races.  There 
were  five  of  these  events  in  all :  Paris-Madrid,  726  miles ;  Paris-Rome, 
910  miles;  the  1,073-mile  European  circuit;  the  1,093  German  route; 
and  the  Tour  of  England,  1,010  miles.  Fowler  completed  his  trans- 
continental trip  by  the  end  of  February,  1912,  landing  in  Jackson- 
ville, Florida. 


735 


32  AVIATION   AND   ITS   FUTURE 

In  addition  to  the  most  striking  performances  already  mentioned, 
numerous  notable  flights  were  made  in  America  on  American-built 
machines.  Though  it  took  12  days  in  all,  Atwood's  flight  from  St. 
Louis  to  New  York  occupied  only  28  hours  53  minutes  actual  flying 
time,  during  which  the  only  attention  required  by  the  engine  was 
the  re-babbiting  of  two  bearings.  Lieutenants  Ellyson  and  Towers  of 
the  United  States  Navy  Aeronautical  Corps  made  a  non-stop  flight 
of  138  miles  over  Chesapeake  Bay  at  56  miles  an  hour  in  the  Curtiss 
navy  hydroaeroplane,  having  just  previously  made  a  non-stop  flight 
of  75  miles.  Hugh  Robinson  made  the  hydroaeroplane  record  of  the 
year  by  his  flight  of  314  miles  down  the  Mississippi  in  three  days, 
carrying  mail.  McCurdy  flew  from  Key  West,  89  miles,  over  the 
Caribbean  and  would  have  landed  in  Havana  a  few  minutes  later, 
but  for  the  breaking  of  the  crank  case  of  his  motor.  Parmalee  and 
Lieutenant  Foulois  flew  106  miles  with  army  despatches  from  Laredo 
to  Eagle  Pass  in  2  hours  10  minutes,  returning  over  the  same  rough 
country  with  but  one  stop.  Beachey  and  Robinson  raced  from 
New  York  to  Philadelphia,  83  miles,  and  Atwood  flew  from  Lynn  to 
Providence  over  the  water  in  2  hours  45  minutes.  M.  B.  Sellers 
flew  with  a  motor  developing  a  scant  6  horse-power,  thus  carrying 
the  exceptional  weight  of  41  pounds  per  horse-power. 

The  seventeen  aeroplane  builders  in  France  turned  out  over 
1,300  machines  in  1911,  the  motors  fitted  to  them  having  an  aggregate 
horse-power  in  excess  of  60,000.  Of  this  total,  813  of  the  aeroplanes 
were  produced  by  only  five  of  the  leading  French  makers.  The 
American  production  is  estimated  at  750  machines,  but  of  these 
more  than  two-thirds  were  built  in  back  yards,  less  than  200  having 
been  turned  out  by  the  Wright,  Curtiss,  Burgess,  and  a  dozen  or  more 
smaller  concerns.  The  actual  total  was  174,  of  which  58  were  for 
private  use,  105  for  exhibition  purposes,  and  11  sold  to  various 
governments.  Out  of  the  total  produced  by  the  five  leading  French 
builders,  410  were  sold  to  various  governments,  367  were  used  in 
exhibitions  and  in  school  work,  and  46  for  sporting  purposes. 

No  new  records  were  made  in  America  in  balloons  or  dirigibles 
during  1911,  though  two  big  races,  the  National  and  the  Gordon- 
Bennett,  were  held  from  Kansas  City.  Germany  and  France  lead 
i*i  the  construction  of  big  airships,  Germany  having  26,  either  belong- 
ing to  the  government  or  available  as  a  military  reserve,  while 


736 


AVIATION   AND   ITS   FUTURE 


33 


France  has  15.  England,  Russia,  Austria,  Italy,  Spain,  Belgium,  and 
Holland  have  25  more.  The  French  airship  "Adjutant  Reau"  holds 
the  record  for  distance,  duration,  and  altitude,  making  a  continuous 


Fig.  12      Side  View  of  Bleriot  "Bus" 


trip  of  550  miles  in  21  hours  20  minutes,  during  which  an  altitude  of 
close  to  7,000  feet  was  reached.  The  German  passenger-carrying 
ship  Schwaben  made  140  trips,  covering  12,670  miles. 


F  g.  13.     Front  View  of  Bleriot  "Bus" 


Passenger  Records.  Up  to  1908,  all  flights  had  been  made  in 
machines  carrying  the  aviator  alone.  The  first  flights  with  passen- 
ger, lasting  more  than  a  few  seconds,  were  those  of  Wilbur  Wright 


737 


34 


AVIATION   AND   ITS   FUTURE 


at  Fort  Myer,  Virginia,  in  September,  1908,  when  he  carried  aloft 
first,  Lieutenant  Lahm  for  6  minutes  26  seconds,  then  Major  Squier, 
U.  S.  A.,  for  9  minutes  6  seconds.  Later  in  the  same  month,  at 
Berlin,  he  carried  a  German  army  officer  aloft  for  1  hour  35  minutes 
47  seconds. 

March  5,  1910,  Hanri  Farman  succeeded  in  carrying  two  passen- 
gers in  the  air,  or  three  persons  all  told,  for  1  hour  2  minutes  25  sec- 
onds. On  April  20,  Roger  Sommer,  in  a  Sommer  biplane,  carried  four 
people — one  a  woman — for  five  minutes,  while  on  August  29,  Louis 
Breguet  took  up  six  persons  all  told,  the  total  weight  sustained  being 
923  pounds.  In  the  fall  of  1910,  Bleriot  built  a  machine  to  carry 


Fig.  14.     Close  View  of  Bleriot  "Bus,"  Showing  Seats  for  Passengers 

regularly  eight  passengers,  i.  e.,  nine  persons  all  told.  Figs.  12  and  13 
show  side  and  rear  views,  while  Fig.  14  shows  details  of  the  car.  This 
machine,  which  was  dubbed  the  "Bleriot  Bus,"  was  very  successfully 
tried  out  in  the  early  spring  of  1911,  making  a  number  of  flights 
which  showed  its  ability  to  make  a  good  speed  despite  the  great 
amount  of  weight  carried.  This  was  in  February,  1911,  and  scarcely 
a  month  had  passed  before  Louis  Breguet  made  an  astounding  flight 
of  3  miles  with  11  passengers  besides  the  aviator,  or  12  people  in  all, 


738 


AVIATION   AND   ITS   FUTURE  35 

at  a  speed  of  55.9  miles  an  hour.  The  weight  of  the  machine  complete 
was  1,322.75  pounds,  and  the  live  load  transported  was  the  same, 
making  the  total  load  taken  aloft  2,645.5  pounds,  or  more  than  1J 
tons,  this  being  the  first  flight  on  record  in  which  the  weight  of  the 
load  has  been  equal  to  that  of  the  machine  itself.  Despite  this  enor- 
mous load  the  aeroplane  rose  without  any  perceptible  difficulty. 
The  machine  was  a  biplane  of  special  design,  built  by  Breguet 
himself. 

Following  this,  Sommer  carried  seven  people  for  1  hour  31 
minutes,  Moineau  took  two  people  for  a  two-hour  cross-country  trip, 
while  the  two-man  altitude  record  was  put  at  9,840  feet  by  Prevost, 
and  the  three-man  distance  record  was  jumped  to  69  miles.  Hirth 
took  a  passenger  from  Munich  to  Berlin,  330  miles,  and  Renaux 
carried  a  passenger  with  him  the  entire  distance  of  the  European 
circuit,  a  race  of  1,073  miles.  These  are  only  the  most  prominent 
passenger-carrying  flights,  it  being  conservatively  estimated  that  the 
French  machines  turned  out  during  1911  alone  carried  a  total  of 
5,000  passengers  during  that  year  while  probably  a  lesser  number 
were  carried  in  all  the  other  countries  put  together. 

At  the  Chicago  Meet  in  August,  1911,  Sopwith  carried  two  people 
besides  himself  in  a  Wright  biplane  at  34.96  miles  per  hour,  while  at 
the  same  meet  Parmalee  carried  458  pounds  weight,  At  the  Nassau 
Meet,  in  September  of  the  same  year,  Lieutenant  Milling  carried  two 
passengers  for  nearly  2  hours. 

Speed.  Speed  records  kept  pace  during  1910  with  those  for 
duration,  passenger/  carrying,  and  altitude,  speeds  in  excess  of  70 
miles  an  hour  having  been  attained,  and  it  was  then  thought  that 
any  increase  over  this  could  be  achieved  only  by  radical  departures  in 
design.  With  the  exception  of  the  record  for  2|  kilometers  (1.5  miles), 
all  records  for  that  year  of  from  5  to  90  kilometers  (3  to  55.8  miles) 
were  made  by  Le  Blanc  in  a  Bleriot  at  one  time — the  Gordon-Bennett 
trophy  race  at  Belmont  Park.  During  1911,  his  figures  were  left  way 
behind  in  every  one  of  the  great  European  races.  Vedrines  made  93 
miles  an  hour  in  a  Morane  monoplane,  while  during  the  Paris-Madrid 
race  he  flew  at  the  rate  of  135  miles  an  hour  with  a  following  gale. 
Weyman  made  an  average  of  78  miles  an  hour  over  a  closed  circuit 
in  a  Nieuport  monoplane,  winning  the  Gordon-Bennett  trophy  for 
America. 


739 


36  AVIATION  AND   ITS   FUTURE 

THE  FLYING  MACHINE  OF  THE  FUTURE 

Now  that  flying  has  become  an  accomplished  fact,  speculation 
as  to  just  what  the  flying  machine  of  the  future  will  be  like  is  quite 
as  rife  as  it  ever  was  when  mankind  generally  regarded  human  flight 
as  one  of  those  long-cherished  illusions,  which,  like  perpetual  motion, 
would  endure  to  torment  the  inventive  mind  as  long  as  the  race 
existed.  Wondrously  impossible  contrivances  as  large  as  the  modern 
sky-scraping  hotel  are  talked  of  and  pictured,  and  the  imagination 
is  drawn  upon  to  supply  details  that  will  probably  never  exist  else- 
where. But  the  developments  of  the  past  few  years  have  been  so 
marvelous  and  so  rapid  that  some  even  of  what  now  appear  to  be 
wholly  fanciful  machines  may  actually  be  built  in  the  future. 

With  all  that  has  been  accomplished  in  the  past  five  years, 
it  is  evident  that  the  first  steps  have  scarcely  been  taken.  The  only 
thing  that  actually  has  been  achieved  is  the  establishment  of  the 
principles  upon  which  human  flight  is  based — those  elusive  laws  of 
science  that  had  been  sought  in  vain  for  centuries  previous.  S'o  far 
as  the  machines  themselves  are  concerned,  they  can  scarcely  be  said 
to  have  advanced  very  much.  They  still  represent  the  same  crude 
assemblage  of  wood,  wire,  and  canvas  that  the  Wright  Brothers 
and  their  numerous  predecessors  were  forced  to  adopt  for  their  experi- 
ments, as  they  represented  the  only  materials  available.  Before 
going  into  this  phase  of  the  matter  at  any  length,  however,  it  will 
be  of  interest  to  take  up  the  question  as  to  just  what  type  of  machine 
is  likely  to  survive. 

Unpromising  Types.  Ornithopter.  It  was  only  logical  that 
first  attempts  at  flight  should  be  patterned  after  nature — many 
were  of  the  opinion  that  if  man  were  ever  to  fly  he  must  imitate  the 
birds.  Strangely  enough,  some  people  are  still  of  this  opinion,  but 
since  flight  based  upon  a  scientific  study  of  the  laws  governing  sus- 
tentation  in  the  air  has  become  a  reality,  they  are  in  the  minority. 
Man's  weight  in  proportion  to  the  power  he  is  able  to  exert  is  so  puny 
in  comparison  with  that  of  the  birds,  as  to  make  any  possibility  of 
development  along  this  line  out  of  the  question.  Flying  with  power- 
driven  wings  is  likewise  extremely  problematical,  as  will  be  apparent 
when  the  weight  that  must  be  sustained  in  the  air  is  taken  into  con- 
sideration. The  mechanism  necessary  to  cause  huge  wings  to  beat 


740 


AVIATION  AND   ITS   FUTURE  37 

in  imitation  of  the  bird  would  not  only  be  weighty  and  complicated 
but  likewise  extremely  inefficient,  as  compared  with  the  propeller- 
driven  soaring  plane,  which  in  itself  has  a  great  deal  of  room  for 
improvement.  Yet  the  hope  of  eventually  being  able  to  fly  with  an 
"ornithopter,"  as  this  type  of  machine  is  termed,  is  not  yet  dead. 
A  Californian,  H.  La  V.  Twining,  has  carried  out  an  unusually  promis- 
ing series  of  experiments  on  a  small  scale,  employing  man  power 
exerted  through  the  medium  of  bicycle  pedals  and  gearing.  It  is 
very  much  to  be  feared,  however,  that  like  the  hot-air  engine  and 
numerous  other  inventions  that  appeared  to  promise  great  results 
from  the  success  achieved  with  a  small  model,  the  ornithopter  would 
be  about  as  cumbersome  and  hopeless  as  its  name,  when  attempted 
on  a  scale  large  enough  to  be  of  any  practical  use. 

Helicopter.  Just  as  there  is  a  certain  class  that  still  looks  to  the 
ultimate  development  of  the  ornithopter,  so  is  there  likewise  another 
class  which  does  not  appear  to  be  influenced  to  any  great  extent  by  the 
fact  that  flight  is  an  established  fact.  This  latter  class  pins  its  faith 
to  the  helicopter — which  affords  a  still  further  example  of  how  mis- 
leading may  be  the  results  obtained  with  a  small  model,  as  related 
by  the  Wright  Brothers  in  their  experience  with  toy  helicopters. 
A  helicopter  consists  essentially  of  a  motor  and  a  propeller,  the  pro- 
peller being  designed  to  rotate  in  a  horizontal  plane  and  to  carry  the 
machine  and  the  aviator  aloft  by  reason  of  its  downward  thrust. 
This  is  the  simplest  type  of  helicopter,  next  to  the  toy  of  the  same 
name,  but  there  are  other  types  which  differ  only  in  the  elaboration 
of  their  detail,  or, in  their  combinations  with  other  elements,  such  as 
planes,  which  tend  to  obscure  their  true  character.  Usually,  two 
propellers  have  been  employed,  designed  to  turn  in  opposite  direc- 
tions, in  order  that  the  tendency  of  one  to  rotate  the  whole  machine 
with  it  could  be  offset  by  the  other.  The  fallacy  of  the  helicopter 
seems  very  self-evident,  and  yet  large  sums  of  money  and  no  little 
inventive  effort  have  been  expended  in  attempting  to  evolve  some- 
thing practical  out  of  the  principle  of  sustentation  by  means  of  the 
thrust  of  a  horizontal  propeller.  If  the  object  of  a  flying  machine 
were  merely  to  shoot  straight  up  into  the  air  from  the  ground  like  a 
rocket,  it  might  be  worth  something  to  be  able  to  start  into  the  air 
without  the  necessity  of  running  along  the  ground,  which  is  the  chief 
advantage  claimed  by  its  advocates,  though  but  one  helicopter  has 


741 


38 


AVIATION  AND  ITS   FUTURE 


742 


AVIATION  AND   ITS   FUTURE 


39 


ever  done  so  with  an  aviator.  But  the  single  reason  for  the  existence 
of  the  aeroplane  is  the  same  as  that  of  the  locomotive,  the  steam- 
ship, the  automobile,  the  bicycle,  and  the  wagon — transportation — 
and  the  ability  to  ascend  straight  up  into  the  air  does  not  bring  with 
it  any  capacity  for  traveling  in  a  horizontal  plane. 

In  addition  to  being  unable  to  move  except  in  a  vertical  plane, 
the  helicopter  likewise  has  the  somewhat  serious  disadvantage  of 
being  totally  without  any  supporting  surface  in  case  of  failure  of 


Fig.  16.     Combination  Dirigible  and  Aeroplane 

the  motive  power,  and  even  with  the  highly  developed  internal  com- 
bustion motor  of  the  present  day,  it  would  indeed  be  a  foolhardy 
aviator  who  would  risk  his  life  in  a  machine  in  which  the  failure  of 
the  power  for  even  a  moment  meant  certain  death.  Paul  Cornu,  a 
Frenchman,  developed  this  type  far  beyond  any  of  his  contempora- 
ries, Fig.  15,  and  he  is  said  to  have  actually  succeeded  in  getting  off  the 
ground,  thus  showing  an  advance  in  that  highly  important  particular 
over  other  helicopter  machines  so  far  built.  This  machine  is  likewise 
an  improvement  in  design,  as  the  propellers  are  so  mounted  that  they 


743 


40  AVIATION  AND   ITS   FUTURE 

can  be  turned  at  an  angle,  as  was  the  case  with  Wellman's  dirigible, 
the  idea  being  that  once  in  the  air  at  the  desired  height,  the  thrust 
of  the  propellers,  or  at  least  one  of  them,  could  be  exerted  in  a  hori- 
zontal direction,  while  the  other  served  as  a  support,  thus  providing 
for  horizontal  travel.  Coming  down  from  a  height  of  9,000  feet  with 
a  dead  motor,  as  has  been  done  in  an  aeroplane,  would  be  a  brief 
and  exciting  experience  in  a  Cornu  helicopter.  Another  attempt  to 
provide  a  means  of  horizontal  travel  took  the  form  of  inclined  planes. 
These  were  not  intended  in  any  way  for  support,  but  merely  to  send 
the  machine  ahead  by  reason  of  the  reaction  of  the  thrust  of  the 
horizontal  propellers  upon  them.  At  the  present  writing,  it  seems 
highly  improbable  that  anything  practical  will  ever  be  done  with 
either  the  ornithopter  or  the  helicopter. 


Fig.  17.     Freak  Type  of  Biplane  Which  Has  Actualy    Flown 

Miscellaneous.  Apart  from  the  types  mentioned,  there  are 
hundreds  that  could  not  be  classified  except  as  freaks,  the  majority 
of  which  are  not  worth  even  passing  mention.  One  of  these,  the  chief 
merit  of  which  appears  to  be  its  novelty,  is  illustrated  in  Fig.  16. 
This  is  a  combination  dirigible  balloon  and  aeroplane,  though  just 
what  is  to  be  gained  in  evolving  such  a  hybrid  is  difficult  to  explain. 
It  is  neither  one  nor  the  other  and  has  the  disadvantages  of  both 
without  the  merits  of  either.  The  gas  bag  is  not  of  sufficient  size  to 
effectually  support  any  weight  while,  on  the  other  hand,  it  is  so  large 
as  to  prove  practically  an  anchor  for  the  aeroplane,  which  could 
make  but  a  very  slow  speed  with  such  an  encumbrance. 


744 


AVIATION   AND   ITS   FUTURE  41 

Another  freak  type,  one  of  the  few  such  machines  that  had  really 
flown,  is  shown  in  Fig.  17. 

Monoplane  vs.  Biplane.  Whether  the  ultimate  flying  machine 
will  be  of  a  type  radically  different  from  those  with  which  we  are  now 
familiar,  or  purely  a  development  of  the  present  types,  is  a  question 
that  can  scarcely  be  answered  satisfactorily.  Any  attempt  to  do  so 
would  be  merely  a  delving  into  the  realms  of  speculation,  and  those 
most  thoroughly  versed  in  the  art  as  developed  up  to  the  present 
day  are  most  reluctant  to  venture  an  opinion.  As  in  other  fields,  it  is 
usually  the  man  who  knows  least  about  the  subject  who  is  anxious 
to  prophesy  a  revolution  in  design.  But  leaving  out  of  consideration 
altogether  the  question  of  the  development  of  some  entirely  new 
type — at  least  new  as  compared  with  the  machines  at  present  in  use, 
such  as  the  ornithopter  and  the  helicopter — there  is  a  great  deal  of 
difference  of  opinion  between  aviators  and  builders  as  to  whether 
the  monoplane  or  the  biplane  will  eventually  reign  supreme. 

The  advocates  of  both  are  equally  enthusiastic  and  equally 
positive  that  the  particular  machine  they  favor  is  the  only  practical 
type.  Even  in  their  present  stage  of  development  both  have  exhibited 
marked  characteristics  and  peculiarities  of  their  own.  The  biplane 
has  great  -stability  and  ease  of  maneuvering  in  the  hands  of  a  skilled 
pilot,  while  the  monoplane  has  carried  away  all  records  for  speed. 
With  the  materials  at  present  employed,  the  biplane  is  an  easier 
machine  to  construct  and  can  likewise  be  made  safer  so  far  as  its 
structure  is  concerned.  It  is  also  an  excellent  weight  carrier,  though 
the  development  of  the  Bleriot  "bus"  which  has  a  capacity  of  eight 
passengers,  shows  mat  the  monoplane  is  not  at  all  lacking  in  this 
respect.  Neither  the  disadvantages  nor  the  advantages  all  lie  with 
either  type — both  have  numerous  merits,  and  where  the  question  of 
speed  is  paramount,  the  superiority  of  the  monoplane  must  be  con- 
ceded. When  a  comparison  of  the  good  and  bad  points  of  the  two  is 
made,  it  seems  evident  that  both  will  always  have  numerous  advo- 
cates and  staunch  supporters,  and  that  unless  something  radically 
new  in  the  design  of  one  makes  it  immeasurably  superior  to  the  other, 
both  will  continue  to  develop  contemporaneously. 

Improvements  in  Construction.  From  an  engineering  point  of 
view  there  can  be  no  question  but  that  the  greatest  room  for  improve- 
ment at  present  exists  in  the  construction.  When  inventors  were 


745 


42  AVIATION   AND   ITS   FUTURE 

struggling  with  the  problem  of  flight,  and  even  for  the  first  few  years 
after  the  principles  which  made  it  possible,  were  definitely  estab- 
lished, there  was  every  reason  why  the  cheapest  and  easiest  materials 
to  obtain  should  be  employed;  likewise  for  their  assembly  in  the 
simplest  and  most  expedient  manner.  Financial  limitations,  if  no 
other,  made  this  imperative.  But  now  that  that  day  has  passed  and 
aeroplane  building  companies,  or  at  least  those  marketing  the  well- 
known  standard  types,  are  possessed  of  ample  capital  and  facilities, 
while  special  materials  are  at  hand  for  the  purpose,  there  appears 
to  be  no  reason  why  the  present-day  crude  assemblage  of  canvas, 
wire,  and  sticks,  which  compose  the  average  biplane  or  monoplane, 
should  continue  to  survive  longer.  Lightness  is  absolutely  essential, 
but  it  can  be  obtained  with  materials  which  have  greater  strength 
and  durability  and  which  may  be  assembled  with  greater  security 
than  is  the  case  at  present,  viz,  steel  and  aluminum,  the  latter 
term  naturally  including  the  numerous  aluminum  alloys  marketed 
under  different  names.  Hardness  and  tensile  strength  have  been 
developed  to  such  a  degree  with  aluminum  and  magnesium  alloys, 
still  preserving,  their  extreme  lightness,  that  there  is  no  longer  any 
reason  for  the  continued  use  of  either  wood  or  canvas.  These 
alloys  are  naturally  far  more  expensive,  while  the  use  of  any  metal 
not  only  involves  greater  manufacturing  cost  but  also  more  difficulty 
in  construction  at  the  outset.  Nevertheless,  it  is  safe  to  say  that  the 
machine  of  the  future  will  be  built  entirely  of  metal. 

A  step  in  this  direction  is  to  be  seen  in  Paulhan's  new  all-steel 
machine,  illustrated  in  Figs.  18  and  19.  In  this,  both  wood  and  cloth 
have  been  dispensed  with  entirely.  The  planes,  as  well  as  the  struts, 
braces,  and  the  like  are  all  of  steel,  and  the  greater  security  of  fasten- 
ing which  this  affords  makes  it  possible  to  eliminate  many  of  the  other- 
wise indispensable  guys,  which,  while  of  small  cross-section  in  them- 
selves, create  considerable  resistance.  That  the  use  of  steel  in  this 
connection  means  weight  saving  is  evident  from  the  fact  that  this 
machine  tips  the  scales  at  only  770  pounds,  although  it  has  a  spread 
of  33.5  feet.  Its  efficiency  is  obvious  from  its  comparatively  small 
supporting  surface  of  470  square  feet.  The  power  plant  consists  of 
a  50-horse-power  revolving  Gnome  motor,  so  that  the  machine  carries 
9.4  pounds  per  square  foot  of  area,  which  is  an  unusually  good  show- 
ing. The  aviator's  seat  and  protecting  car  containing  all  the  controls 


746 


AVIATION   AND   ITS   FUTURE 


43 


is  placed  between  the  main  planes,  which  marks  a  radical  departure 
from  the  customary  plan  of  placing  them  on  the  lower  plane  frame. 


Fig.  18.      Paulhan's  Ail-Steel  Biplane 

This  construction  would  hardly  be  permissible  upon  the  usual  wood- 
frame  biplane,  as  the  struts  to  support  the  aviator's  weight  would 


Fig.  19.     Paulhan's  All-Steel  Biplane  in  Flight 

have  to  be  very  much  heavier  than  usual,  while  the  necessary  brac- 
ing to  hold  the  seat  rigid  would  also  involve  weight  to  an  almost 
prohibitive  extent. 


747 


44  AVIATION   AND   ITS   FUTURE 

That  aviators  generally  have  had  in  mind  the  employment  of 
metal  for  construction  is  evident  from  numerous  instances.  John 
D.  Moissant,  who  was  the  first  to  fly  from  Paris  to  London  and 
whose  skill  and  daring  gained  him  many  admirers,  completed  sev- 
eral months  before  his  death  at  New  Orleans,  in  December,  1910, 
the  design  of  a  monoplane  to  be  built  entirely  of  aluminum.  Such 
a  machine  was  constructed  and  undoubtedly  would  have  been 
successfully  developed,  had  its  inventor  lived.  Quite  a  number  of 
others  have  since  built  machines  either  partly  or  entirely  of  metal 
and  the  strong  tendency  toward  its  use  was  very  marked  in  the 
machines  exhibited  at  the  Paris  Salon,  December,  1911.  Damage  to 
a  metal  framed  and  winged  aeroplane  is  naturally  much  more  diffi- 
cult and  expensive  to  repair  so  that  the  use  of  steel  and  aluminum 
can  hardly  become  general  until  the  experimental  stage  is  left  behind. 
The  necessity  for  warping  the  wings  in  accordance  with  the  pria- 
ciples  laid  down  by  the  Wright  Brothers,  a  device  which  is  now 
almost  universally  employed,  presents  no  particular  difficulties  of  con- 
struction in  connection  with  the  use  of  a  metal  supporting  surface. 

Racing  Machine  of  the  Future.  As  the  result  of  a  study  of 
recent  developments,  J.  Bernard  Walker  has  outlined  in  the  Scientific 
American,  the  plan  of  the  racing  machine  of  the  future,  as  follows: 

The  future  high-speed  flyer  will  possess  the  same  tapering,  rounded 
body  and  the  narrow,  wide-spread  wings  which  characterize  the  swiftest  of 
birds— the  albatross.  Langley  showed  that  the  leading  portion  of  the  plane 
is  most  efficient  because  it  is  constantly  moving  on  to  fresh,  undisturbed 
bodies  of  air.  As  the  after  portion  of  the  plane  has  to  work  upon  air  which  has 
already  received  a  downward  velocity,  this  air  is  unable  to  exert  the  effective 
reaction  provided  by  air  that  is  inert.  Hence,  a  plane  5  feet  wide  by  10  feet 
long  becomes  more  efficient  when  divided  longitudinally,  making  it  2\  feet 
wide  by  20  feet  long.  The  wings  will  accordingly  be  long  and  narrow,  and 
when  made  of  metal,  it  will  be  possible  to  give  them  the  sweeping,  rounded 
forms,  which  prevent  eddy  making.  The  body  will  be  of  a  generally  circular 
or  oval  section  and,  to  allow  of  a  long  and  gradual  taper  for  ease  in  traversing 
the  air,  will  have  considerable  length,  this  adding  greatly  to  the  fore-and-aft 
stability  in  flight.* 

The  present  wood,  canvas,  and  wire  construction  will  have  to  go.  It 
is  a  makeshift  at  the  best  and  was  adopted  because,  in  the  early  days  of  experi- 
ment, it  offered  a  cheap  and  light  combination  of  material,  and  one  which,  in 
the  event  of  the  inevitable  breakages,  could  be  cheaply  and  quickly  repaired. 
Its  place  will  be  taken  by  some  of  the  many  remarkable  alloys  of  steel  now 


*Several  bodies  of  this  type  were  shown  on  some  of  the  French  machines  at  the  Paris 
Salon,  December  1911. — Ed. 


743 


AVIATION   AND   ITS   FUTURE  45 

available — metals  of  enormous  strength  and  toughness  in  proportion  to  their 
weight.  The  use  of  these  coupled  with  careful  designing  by  the  skilled  engineer, 
will  make  it  possible  to  produce  an  aeroplane  of  much  greater  strength  that 
will  weigh  no  more  than  the  present  machine,  and  will  present  far  less  resistance. 

The  principal  resistances  encountered  by  an  aeroplane  are  those  due 
to  the  lift  and  the  head  surface.  That  due  to  the  lift  is  fairly  constant,  for  as 
the  speed  increases,  the  angle  of  incidence  decreases,  and  there  is  always  an 
adjustment  between  the  two  which  provides  sufficient  vertical  reaction  at  all 
times  to  lift  the  weight  of  500  to  1,000  pounds,  as  the  case  may  be.  The  head 
resistance,  however,  increases  approximately  as  the  square  of  the  speed,  and 
if  it  be  100  pounds,  say  at  40  miles  an  hour,  it  will  rise  to  400  pounds  at  80  miles 
an  hour.  Hencs,  in  a  racing  machine,  the  great  importance  of  reducing  the 
head  surface  to  the  least  possible  limit  consistent  with  structural  requirements. 
It  is  this  consideration  of  head  resistance  which  has  doomed  the  biplane  as  a 
purely  racing  type.  When  Octave  Chanute  built  the  first  biplane  glider,  with 
its  light  but  very  rigid  Pratt  trussing  of  vertical  wood  struts  and  diagonal 
wire  tires,  he  produced  an  excellent  piece  of  engineering  construction,  which 
has  proved  to  be  ideally  adapted  to  the  early  experimental  stage  which  is  now 
drawing  to  its  close.  But  for  high-speed  results,  because  of  the  large  amount 
of  head  surface  presented,  the  Pratt  truss  was  doomed  to  ultimate  extinction. 
Unquestionably,  the  higher  speed  attained  by  the  monoplane  is  due  largely 
to  the  fact  that  its  trussing  is  simpler,  and  the  head^  surface,  particularly  of 
the  wire  stays,  is  relatively  much  less.  The  great  amount  of  resistance  offered 
by  the  apparently  negligible  surface  of  the  thin  wires  was  shown  by  Langley's 
experiments  to  be  due  to  the  fact  that  the  rate  of  vibration  of  the  wire  under 
the  rush  of  air  is  so  great  that  it  practically  presents  a  solid  surface,  the  width 
of  which  is  equal  to  the  amplitude  of  vibration.  Hence,  a  tightly-strung  wire 
offers  an  amount  of  resistance  which  is  seemingly  out  of  all  proportion  to  its 
actual  surface. 

It  follows,  then,  that  even  the  simple  king-pin  trussing  of  the  Bleriot 
and  Antoinette  types  must  go  if  we  are  to  achieve  the  highest  speed  which  is 
predicted  for  the  future  racing  machine.  This  will  be  possible  only  if  some 
high-grade  sheet  metal  is  substituted  for  the  canvas  of  the  wing  surface,  and 
the  necessary  transverse  bending  strength  is  secured  by  means  of  plate-steel 
members  enclosed  within  the  wing  surfaces  and  strongly  riveted  to  the  structure 
of  the  main  body  of  the  machine.  Turning  to  nature  for  guidance  again,  we 
find  that  the  fast-flying  birds  fold  their  legs  snugly  beneath  them  w;hen  in 
flight.  The  racing  aeroplane  must  do  the  same. 

Mr.  Walker  goes  on  at  some  length  detailing  the  construction 
of  such  a  machine,  as  well  as  of  a  special  folding  chassis,  operated 
by  compressed-air  cylinders,  which  would  act  to  cushion  the  shock 
of  landing.  He  also  purposes  to  operate  the  movable  wing  tips  by 
similar  power,  a  two-way  valve  to  the  cylinders  being  controlled  by 
a  gyroscope,  which  may  be  rendered  inoperative  when  it  is  desired 
to  make  a  turn.  After  it  has  been  sufficiently  developed  by  experi- 
mental work,  he  thinks  it  conservative  to  expect  a  speed  of  100  to 


749 


46  AVIATION   AND   ITS   FUTURE 

125  miles.  As  nearly  80  miles  per  hour  has  already  been  attained 
with  the  present  construction,  this  estimate  does  not  appear  to  be 
overdrawn.* 

Reefed  Supporting  Surfaces.  Another  feature  that  is  likely 
to  become  a  subject  of  attention  shortly  and  which  wiH  undoubtedly 
have  considerable  influence  on  the  development  of  the  machine  of 
the  future,  is  that  of  a  variable  supporting  area;  in  other  words, 
a  method  of  "reefing"  the  supporting  surface  to  adapt  its  area  to  the 
speed  of  the  machine.  Aeroplane  speeds  have  already  reached  a 
point  where  this  is  to  the  fore.  The  demand  for  a  variable  surface 
is  based  upon  one  of  the  most  important  of  the  laws  of  flight,  viz,  that 
the  area  of  the  necessary  supporting  surface  of  an  aeroplane  varies 
inversely  as  the  square  of  the  velocity.  This  principle,  affirmed 
by  Langley  and  embodied  in  his  great  work  "Experiments  in  Aero- 
dynamics," has  been  disputed  by  some  European  theorists  and 
practical  aeroplane  builders,  but  the  experience  of  the  past  two  years 
appears  to  verify  it. ,  If  the  law  holds  good,  the  standard  Wright 
biplane  of  1910,  which,  with  about  500  square  feet  of  surface,  has 
a  speed  of  40  miles  an  hour,  at  60  miles  would  need  only  222  square 
feet  for  support,  and  at  100  miles,  only  80  square  feet. 

That  the  principle  is  generally  correct,  or,  at  least,  that  its  appli- 
cation does  not  produce  too  great  a  reduction  of  surface,  is  shown 
by  the  racing  machines  exhibited  and  flown  by  the  Wright  Brothers 
at  the  International  Meet  in  the  autumn  of  1910.  One  of  these,  a 
semi-racer  with  a  speed  of  60  miles  an  hour,  was  provided  with  only 
150  square  feet  of  supporting  surface.  The  standard  Wright  machine, 
driven  at  60  miles  an  hour,  would  need,  according  to  this  law,  222 
square  feet.  Its  weight,  however,  with  the  aviator  and  full  fuel  and 
water  supply,  is  1,075  pounds,  whereas  the  semi-racer  weighs  with 
pilot  and  fuel  only  760  pounds.  The  difference  in  weight  would 
account  largely  for  the  reduction  of  the  area  from  222  to  150  square 
feet  of  sustaining  surface.  Further  verification  is  found  in  the  Bleriot 
racer,  which,  with  slightly  less  speed,  and  a  weight  of  about  '650 
pounds,  including  the  aviator,  also  has  less  than  150  square  feet  of 
sustaining  surface.  It  is  significant  that  in  their  actual  racing 
machine,  which  is  15  miles  an  hour  faster,  the  Wrights  did  not 


*The  internally  braced  wing  came  into  existence  in  the  Antoinette  armored  monoplane 
(see  Special  Types)  in  1911,  and  the  100-mile  an  hour  mark  was  reached  in  February,  1912 
(see  Aviation  Records) . 


750 


AVIATION   AND   ITS   FUTURE  47 

attempt  to  reduce  the  supporting  surface  any  further,  both  the  semi- 
racer  and  the  racer  having  150  square  feet  of  surface.  The  racer, 
however,  is  heavier,  weighing  about  900  pounds  ready  to  fly. 

If,  then,  the  high-speed  flyers  endorse  Langley's  law,  it  follows 
that  there  will  be  a  further  reduction  of  area  in  the  racing  machines 
of  the  future.  If  the  standard  Wright  machine  with  500  square  feet 
of  surface  could  be  driven  at  100  miles  an  hour,  it  would  need  only 
80  square  feet  of  surface  for  support,  and  if  a  speed  greater  than  100 
miles  per  hour  were  accomplished,  the  sustaining  surface  would 
come  down  to  a  pair  of  long,  narrow  blades,  approximating  in  form 
the  wings  of  the  swift  or  the  swallow.  But  it  must  be  remembered 
that  these  reduced  surfaces  are  equal  to  their  work  only  if  the  machine 
is  being  driven  at  its  highest  or,  at  least,  at  a  high  velocity;  and 
they  are,  therefore,  theoretically  too  small  to  lift  the  machine  from 
the  ground  or  allow  it  to  return  safely  at  the  lowest  speeds  which  are 
necessary  in  starting  and  alighting.  Proof  of  this  was  shown  in  the 
accident  which  disabled  the  Wright  racing  machine  in  the  contest 
for  the  international  trophy  at  Belmont  Park,  when  the  stopping 
of  the  motor  and  the  sudden  slowing  down  of  the  biplane  caused  it 
to  drop  so  swiftly  to  the  ground  that  its  momentum  partially  wrecked 
the  machine  and  threw  the  aviator  from  his  seat.  Probably,  having 
been  accustomed  to  the  larger  surface  Wright  machine,  he  did  not 
realize  the  necessity  of  descending  with  the  main  planes  at  a  large 
angle  of  incidence  in  order  to  check  the  velocity.  In  any  case  it  is 
evident  that  if  the  racing  aeroplane  reaches  a  speed  of  100  miles  an 
hour,  it  will  be  necessary  for  safe  control  to  provide  it  with  some 
means  of  enlarging  or  reducing  the  supporting  area  proportionately 
to  the  speed,  or  of  altering  the  angle  of  incidence  of  the  wings  to 
generate  increased  resistance  for  alighting  safely. 

This  problem  should  not  be  particularly  difficult  of  solution. 
The  additional  surface  could  be  arranged  to  be  drawn  under  or  within 
the  main  surfaces  either  from  the  ends  or  from  the  rear.  If,  as  seems 
quite  likely,  the  aeroplanes  of  the  future  be  built  entirely  of  metal, 
the  problem  will  be  much  easier  to  work  out.  A  large  percentage  of 
the  accidents  to  existing  machines  are  due  to  descending  and  landing 
at  too  great  an  angle  or  at  too  great  a  speed.  Were  it  possible  volun- 
tarily to  increase  the  surface  at  the  time  of  making  a  landing,  the 
risk  of  accident  from  this  cause  would  be  greatly  reduced. 


751 


48  AVIATION   AND   ITS   FUTURE 

Duplicate  Power  Plant.  Another  trend  of  development  that 
is  receiving  considerable  attention  is  the  design  of  an  aeroplane  pro- 
vided with  two  motors,  either  one  of  which  may  be  employed  to  drive 
the  propeller  or  propellers,  in  order  to  avoid  the  necessity  of  alight- 
ing should  the  motor  stop,  as  is  the  case  with  present  machines. 
Such  a  contingency  involves  no  great  danger  when  flying  over  an 
aviation  field,  but  in  cross-country  flights  the  matter  of  finding  a 
suitable  place  to  alight  in  an  emergency  is  something  that  the  aviator 
prefers  not  to  have  to  decide.  Edwin  Gould  has  offered  a  prize  of 
$15,000  for  a  successful  machine  of  this  type,  which  will  be  com- 
peted for  through  the  Scientific  American. 

In  the  foregoing,  no  attempt  has  been  made  to  point  out  all  the 
possibilities  of  the  future  machine.  So  much  has  been  accomplished 
in  such  a  marvelously  short  period  and  so  much  will  undoubtedly 
be  brought  about  in  the  next  few  years,  that  it  would  be  idle  to  do 
more  than  bring  to  notice  a  few  of  the  salient  features  which  most 
likely  will  receive  the  greatest  share  of  attention  in  the  near  future. 


752 


r 


k 


m 


GLOSSARY 


Acceleration.     The  rate  of  change  of  velocity  of  a  moving  body. 

Adjusting  Plane.  A  smaller  plane  of  an  aeroplane,  generally  placed  at  the 
end  of  the  wing  tip  and  adjusted  to  maintain  lateral  balance.  A  stabilizer 
placed  at  the  end  of  a  wing  tip. 

Adjusting  Surface.     See  Adjusting  Plane. 

Advancing  Edge.  The  front  edge  of  any  of  the  surfaces  of  a  heavier-than- 
air  flying  machine.  Synonymous  with  Attacking  Edge. 

Advancing  Surface.  A  surface  of  an  aeroplane  that  is  ahead  of  another 
surface. 

Aerial.     See  Antennae. 

Aerodrome.  A  ground  set  apart  for  flying  purposes.  (Langley's  term  for 
his  flying  machines.) 

Aerodynamics.  The  science  of  atmospheric  laws,  i.e.,  the  effects  produced 
by  air  in  motion. 

Aerofoil.     A  substitute  proposed  for  Aeroplane. 

Aeronat  (air  swimmer).     A  term    sometimes    applied  to  dirigible    balloons. 

Aeronaut.     An  aerial  navigator. 

Aeronautics.     The  entire  science  of  aerial  navigation. 

Aeronef.  Proposed  term  for  flying  machine.  (Not  likely  to  come  into 
general  use.) 

Aeroplane.     A  power-driven  heavier-than-air  machine. 

Aerostat.  A  lighter-than-air  flying  machine  depending  upon  the  use  of  a 
volume  of  gas  whose  specific  gravity  is  less  than  that  of  the  air,  but  hav- 
ing no  means  of  lateral  guiding;  an  ordinary  balloon. 

Aerostatics.     The  science  o'f  buoyancy  in  the  air  by  displacement. 

Aerostation.  That  part  of  the  science  of  aeronautics  that  deals  with  "lighter- 
than-air"  or  gas-lifted  machines. 

Aileron  (French).  A  small  wing  or  plane,  either  attached  to  the  rear  edge 
of  the  main  planes  as  in  the  Farman,  or  between  them  as  in  the  Curtiss 
biplane. 

Air  Bag.  One  of  several  small  bags  within  a  balloon.  These  bags  are  con- 
nected with  an  air  pump,  and  by  increasing  or  decreasing  the  amount 
of  air  in  the  bags  the  pressure  of  gas  within  the  balloon  may  be  regulated. 
Also  called  Balloonet. 

Air-Resistance.  The  resistance  encountered  by  a  surface  in  motion.  This 
resistance  increases  as  the  square  of  the  speed,  which  makes  it  necessary 
to  employ  four  times  as  much  power  in  order  to  double  a  given  speed. 
A  monoplane  has  usually  less  resistance  than  a  biplane,  which  accounts 
for  the  greater  speed  of  the  former.  While  it  is  desirable  to  reduce  this 
retarding  force  to  a  minimum,  a  certain  amount  of  resistance  is  required 
to  produce  sustentation  in  the  air. 

Copyright,  1912,  by  American  School  of  Correspondence. 


753 


2  GLOSSARY 

Airship.     A  dirigible  balloon. 

Alighting  Gear.  The  mechanism  on  the  under  part  of  an  aeroplane  to  cushion 
its  descent  and  bring  it  to  a  stop  upon  reaching  the  ground.  It  usually 
consists  of  pneumatic-tired  wheels  with  a  spring  frame,  or  of  skids,  the 
starting  gear  and  alighting  gear  nearly  always  being  combined.  Also 
called  Running  Gear. 

Anemometer.  An  instrument  for  measuring  the  force  or  velocity  of  the 
wind,  or  both.  Anemometers  are  made  of  several  types:  (1)  Suction  and 
pressure  anemometers,  which  indicate  in  a  more  or  less  direct  manner  by 
the  deflection  of  a  spring  or  of  a  suspended  plate  of  accurately  deter- 
mined weight,  or  by  causing  water  to  rise  in  a  tube.  (2)  Rotating  anemom- 
eters which,  by  the  continual  revolution  of  a  horizontal  spider  carrying 
vanes  or  cups  at  the  ends  of  its  arms,  directly  indicates  a  measure  of  its 
movement  from  which  its  velocity  may  be  computed.  Some  anemometers 
indicate  the  distance  traveled  by  the  wind  in  a  specified  time,  from  which 
its  velocity  can  be  calculated. 

Angle  of  Attack.     Practically  synonymous  with  Angle  of  Incidence. 

Angle  of  Incidence.  The  angle  that  a  plane  makes  with  an  imaginary  hori- 
zontal line  when  flying. 

Antennae.  Wire  or  wires  for  intercepting  electromagnetic  radiations  in  the 
air  and  leading  them  to  "wireless"  receiving  instruments. 

Arch.     A  downward  curve  given  the  ends  of  a  winged  surface. 

Area,  Effective.  This  usually  covers  the  entire  area  of  the  flying  machine, 
including  elevating  planes  as  well  as  the  main  planes,  and  is  that  of  the 
plan  form,  so  that  it  is  measured  in  units  of  double  surface,  i.e.,  both 
sides  or  surfaces  are  counted  as  one  unit  of  area.  Thus,  by  an  area  of 
500  square  feet  is  indicated  a  surface  of  twice  500  square  feet. 

Area,  Supporting.     See    Area,    Effective. 

Aspect  Ratio.  The  proportion  that  the  length  or  "spread"  of  the  supporting 
surfaces  bear  to  their  depth. 

Aspiration.  The  action  of  a  current  of  air  flowing  against  the  edge  of  a  spiral 
curved  wing  or  aeroplane  surface,  by  which  the  surface  is  drawn  toward 
the  current;  also  called  tangential  force. 

Automatic  Stability.  The  maintaining  of  lateral  and  longitudinal  stability 
of  a  flying  machine  independently  of  the  control  of  the  operator. 

Aviation.     The  science  of  dynamic  flight  by  means  of  heavier-than-air  machines. 

Aviator.  The  operator  of  a  heavier-than-air  flying  machine.  Strictly,  the 
form  of  flying  machine. 

B 

Balance,  Dynamic.     Equilibrium  of  the  machine  in  flight.  .  See  Stability. 

Balance,  Static.  Standing  balance;  equilibrivn  of  the  machine  when  sta- 
tionary on  the  ground. 

Balancing  Plane.  A  surface  whose  position  or  angle  may  be  changed  to  steer 
or  maintain  balance. 

Balancing  Surface.     Same  as  Balancing  Plane. 

Banking.  The  tilting  of  an  aeroplane  to  increase  its  resistance  and  prevent 
skidding  or  "sliding  off"  in  rounding  a  turn. 


754 


GLOSSARY  3 

Barograph.     An  automatic  recording  barometer  employed  to  record  the  height 

to  which  an  aeroplane  or  dirigible  ascends. 
Biplane.     An  aeroplane  with  two  superposed  main  planes  overlapping  in  plan 

form. 

c 

C.     Abbreviation  for  a  centigrade  degree  of  temperature. 

C.  G.  S.  System.  Abbreviation  for  centimeter-gram-second  system  of  meas- 
urement; the  standard  system  in  scientific  work. 

Camber.     The  greatest  depth  of  curvature  of  a  surface  or  plane. 

Canard  (French  "Duck").  A  type  of  monoplane  or  biplane  that  has  all 
auxiliary  surfaces  in  front  and  apparently  flies  backward.  So  called 
owing  to  its  resemblance  to  a  duck  in  flight. 

Cavitation.  Effect  of  revolving  a  propeller  at  an  excessive  speed  for  its  pitch 
and  diameter,  creating  a  "hole,"  so  to  speak.  The  fluid,  water  or  air,  is 
carried  round  by  the  blades  of  the  propeller  in  the  same  plane,  instead  of 
being  thrust  back. 

Center  of  Effort.     See  Center  of  Thrust. 

Center  of  Gravity.     The  point  of  a  body  about  which  all  portions  are  balanced. 

Center  of  Lift.     A  mean  of  all  the  centers  of  pressure. 

Center  of  Pressure.  A  line  along  the  under  side  of  an  aeroplane  surface,  on 
either  side  of  which  pressures  are  equal. 

Center  of  Thrust.  A  point  or  line  along  which  the  thrust  of  the  propellers 
is  balanced. 

Centigrade  Scale.  The  thermometer  scale  invented  by  Celsius.  Used  uni- 
versally in  scientific  work. 

Centripetal  Force.  A  force  tending  to  draw  things  toward  a  center  (as  opposed 
to  centrifugal  force). 

Chord.  An  imaginary  straight  line  connecting  the  ends  of  the  arch  or  camber 
of  a  plane. 

Cloche  (bell).     Bell-shaped  device  employed  in  the  Bleriot  control. 

Control,  Longitudinal.  This  consists  of  the  elevating  rudder  and  its  operating 
connections. 

Control,  Throttle.  Method  of  governing  the  power  of  the  engine  by  altering 
the  area  of  the  passage  leading  to  the  admission  valve  so  that  the  amount 
of  the  fuel  introduced  into  the  cylinder  is  varied. 

Control,  Transverse.  Levers  and  connections  for  warping  the  wings  or  mov- 
ing ailerons  to  maintain  transverse  stability. 

Critical  Speed.  Rate  of  travel  at  which  an  aeroplane  propels  and  sustains 
itself  most  efficiently. 

D 

Dead  Surfaces.  Those  which  exert  no  lifting  power,  such  as  fins,  keels,  non- 
lifting  tails,  etc. 

Depth.     Dimension  of  a  plane  parallel  to  its  direction  of  flight. 

Dihedral  Angle.  Upward  inclination  of  the  planes  at  an  angle  to  each  other 
in  the  form  of  a  V. 

Direction  Rudder.  The  vertical  rudder  by  means  of  which  an  aeroplane  or 
dirigible  is  guided  in  exactly  the  same  manner  as  a  ship. 


755 


4  GLOSSARY 

Dirigible.     Steerable;    drivable;    usually    applied    to    lighte.-than-air    flying 

machines  which  may  be  propelled  and  guided. 
Disk.     The  circle  of  air  upon  which  a  propeller  acts. 
Drift.     The  resistance  of  an  aeroplane  surface  to  forward  movement. 
Drome.     Word  suggested  for  the  flight  of  aeroplanes. 


Elevating  Rudder.  A  horizontal  rudder  or  plane,  the  angle  of  incidence  of 
which  may  be  altered  to  cause  an  aeroplane  or  dirigible  to  ascend  or 
descend. 

Elevator.     A  horizontal  rudder  for  steering  upwards  or  downwards. 

Empennage  (French).  Feathering  of  an  arrow — as  applied  to  the  rear  sta- 
bilizing planes  of  a  dirigible. 

Epinage  (French).  Tail — all  of  that  part  of  an  aeroplane  back  of  the  main  sup- 
porting surfaces,  particularly  as  applied  to  a  monoplane. 

Equilibrator.  A  device  designed  to  automatically  increase  or  decrease  the 
amount  of  ballast  of  a  dirigible  flying  over  water.  Obsolete. 


Fin.  (1)  A  vertical  surface  or  plane  designed  to  aid  the  lateral  stability  of 
the  aeroplane.  Synonymous  with  keel.  (2)  Projections  cast  on  the 
cylinder  of  a  gas  engine  to  assist  in  cooling. 

Flexible  Propeller.  A  propeller  whose  fabric  is  rather  loosely  mounted  on  a 
framework  so  that  it  can  change  its  form  with  the  varying  air  pressures, 
or  one  in  which  stiff  blades  are  pivoted  and  controlled  manually  or  by 
springs  to  enable  the  aviator  to  alter  the  pitch  in  accordance  with  the 
speed. 

Flying  Angle.     The  angle  of  incidence  of  aeroplane  surfaces  in  flight. 

Flying  Machine.  An  apparatus  designed  to  enable  persons  to  move  about 
at  will  through  the  air.  Strictly,  the  term  should  be  applied  to  only 
that  class  of  machines  in  which  human  flight  is  obtained  by  means  of 
flapping  wings. 

Following  Edge.     The  rear  edge  of  an  aeroplane  surface. 

Following  Surface.     A  main  surface  that  is  preceded  by  another. 

Fore-and-Aft  Stability.     See  Longitudinal  Stability. 

Fuselage  (French).  The  framework  of  an  aeroplane  as  distinguished  from 
the  planes  themselves. 

Q 

Gas.  Matter  in  a  fluid  form  which  is  elastic  and  has  a  tendency  to  expand 
indefinitely  with  reduction  in  pressure. 

Gas  Bag.  A  gas-tight  bag  designed  to  contain  gas,  usually  applied  to  the 
envelope  of  a  balloon. 

Gauchissement    (French).     Warping,    also    banking. 

Glider.     An  aeroplane,  without  motor  or  propeller,  for  use  in  gliding. 

Gliding.  The  combination  of  forward  and  downward  movement  of  an  aero- 
plane without  power. 


758 


GLOSSARY  5 

Gliding  Angle.     The  smallest  angle  at  which  an  aeroplane  is  able  to  glide. 
Gong.     A  loud,  clear-sounding  bell  usually  operated  either  electrically  or  by 

foot  power. 
Gyroplane.     A  heavier-than-air  flying  machine  lifted  by  rotating  aeroplanes; 

a  helicopter. 
Gyroscope.     A  heavy  wheel  revolving  at  high  speed,  the  gyroscopic  effect  of 

which  is  employed  to  give  automatic  stability. 
Gyroscopic  Effect.     That  property  of  a  rotating  body  by  virtue  of  which  it 

tends  to  maintain  its  plane  of  rotation  against  all  disturbing  forces. 

H 

Hangar    (French).     Building    used    for    harboring    aeroplanes.     Synonymous 

with  "shed,"  "loft,"  etc. 

Head  Resistance.     The  resistance  of  a  surface  to  movement  through  the  air. 
Head  Surface.     The  edges  of  the  planes,  struts,  etc.,  presented  to  the  wind 

and  causing  resistance  to  flight. 
Heavier-Than-Air.     A  term  applied  to  dynamic  flying  machines  which  weigh 

more  than  the  air  they  displace. 
Helicopter.     From  helix,  a  screw.     A  dynamic,  heavier-than-air  flying  machine, 

designed  to  be  sustained  by  the  effect  of  screws  or  propellers  mounted  on 

vertical  axes  and  rotating  in  a  horizontal  plane. 
High-Tension  Current.     A  current  of  high  voltage,  as  the  current  induced  in 

the  secondary  circuit  of  a  spark  coil. 

Horizontal  Component.     Amount  of  force  acting  to  drive  the  aeroplane  ahead. 
Horizontal  Rudder.     A  rudder  placed  horizontally  for  steering  in  a  vertical 

plane. 
Hovering.     That  method  of  flight  in  which  a  practically  fixed  position  in  the 

air  is  held. 
Hydroaeroplane.     An  aeroplane  fitted  with  floats  or  boats  and  designed  to 

arise  from  and  alight  on  the  water. 
Hydroplane  or  Hydroplane  Float.     One  having  its  under  surface  so  curved  that 

it  rises  and  skim^  the  surface  of  the  water  when  traveling  at  high  speed 

I 

Incident  Angle.     See  Angle  of  Incidence. 

Inherent  Stability.  Stability  of  an  aeroplane  due  to  its  design  and  arrange- 
ment of  supporting  surfaces,  as  distinguished  from  automatic  stability 
due  to  an  extraneous  device  or  attachment. 

K 

"K."  Symbol  denoting  a  constant,  or  coefficient,  used  in  calculating  air  resist- 
ance. 

Keel.  The  underframing  placed  longitudinally  under  flying  machines  to 
stiffen  the  structure.  More  usually  employed  in  dirigible  balloons. 


757 


GLOSSARY 


Landing  Area.     A  specially    prepared    surface    for    the    alighting    of    flying 

machines. 

Lateral  Stability.     Stability  in  a  lateral  direction,  or  from  side  to  side. 
Leeway.     Movement  at  right  angles  to  the  course  being  steered,  caused  by  the 

lateral  drift  of  the  atmosphere  or  by  centrifugal  force  acting  on  the  aero- 
plane in  rounding  a  turn. 

Lift.     The  sustaining  effect  of  a  wing  surface  or  aeroplane  surface. 
Lighter-Than-Air.     A  term  applied  to  an  airship  weighing  less  than  the  air 

displaced  by  it. 
Locus  (Latin).     Point,  or  place,  as  referred  to  in  describing  movement  of  center 

of-  pressure. 

Longitudinal  Stability.     Stability  in  the  longitudinal  direction. 
Lubrication,  Splash.     Method  of  lubricating  an  engine  by.  feeding  oil  to  the 

crank  case  and  allowing  the  lower  edge  of  the  connecting  rod  to  splash 

into  it. 
Lubricator.     A    device    containing    and    supplying    oil    or    grease   in    regular 

amounts  to  the  working  parts  of  the  machine. 

M 

Main  Plane.     The  main  supporting  surface  of  an  aeroplane. 
Monoplane.     An  aeroplane  having  one  main  supporting  surface. 
Meteorology.     The  science  that  treats  of  atmospheric  conditions,  their  changes, 
and  effects. 

N 

Non-Lifting  Tail.     An  auxiliary  surface  at  the  rear  of  an  aeroplane  which  does 
not  aid  in  the  support  of  the  machine. 

o 

Ornithopter.     A  heavier-than-air,  or  dynamic,  flying  machine  in  which  flap- 
ping wings  are  used  for  lifting  and  propulsion. 
Orthogonal.     A  term  used  to  designate  flapping  flight. 
Orthopter.     Another  spelling  for  Ornithopter. 


Panel.     A  vertical  surface.     Analogous  to  keel  and  fin. 

Peripheral  Speed.     Rate  at  which  the  tips  of  the  propeller  blades  travel  in 

rotating. 
Pilot.     The  operator  of  a  flying  machine.     Strictly,  one  who  is  licensed  by 

an  aeronautic  club. 

Pisciform.     Fish-shaped,  as  applied  to  the  envelope  of  a  dirigible. 
Pitch.,    The  theoretical  distance  traveled  forward  or  backward  by  a  screw 

propeller  in  one  complete  revolution. 
Pitch,  Variable.     An  increasing  or  decreasing  pitch,  as  applied  to  a  propeller 

blade,  in  contrast  with  the  true  screw. 
Pitch  Coefficient.     See  Pitch  Ratio. 


758 


GLOSSARY  7 

Pitch  Ratio.     The  proportion  that  the  pitch  of  a  propeller  bears  to  its  diameter. 

Plane.     A  flat,  or  approximately  flat,  surface. 

Propeller  Reaction.     The  tendency  of  a  single  propeller  to  revolve  the  vehicle 

to  which  it  is  attached  in  the  opposite  direction. 
Pylon  (French).     A  pole  placed  on  an  aviation  field  to  mark  the  course. 

R 

Reactive  Stratum.  The  stratum  of  air  which  is  compressed  beneath  an  aero- 
plane surface  or  behind  the  blade  of  a  propeller. 

Resiliency.  That  property  of  a  material  by  virtue  of  which  it  springs  back 
or  recoils  on  removal  of  pressure,  as  a  spring. 

Rib.     A  part  of  an  aeroplane  to  give  the  correct  shape  to  the  wing  section. 

Rigid  Type  Dirigible.  An  airship  in  which  the  envelope  is  supported  on  a 
frame  and  docs  not  depend  upon  its  inflation  to  maintain  its  form. 

Rising  Angle.     The  angle  at  which  an  aeroplane  ascends. 

Rudder.     A  surface  for  steering. 

Runner.  A  part  of  alighting  gear  used  in  place  of  wheels,  and  resembling 
sled  runners.  Also  called  skid. 

Running  Gear.  The  landing  chassis,  or  frame  and  wheel  arrangement,  by 
means  of  which  the  aeroplane  runs  along  the  ground  and  upon  which  the 
aeroplane  lands  at  the  end  of  a  flight. 


Semi-Rigid  Type  Dirigible.  One  having  the  car,  motors,  etc.,  supported  by  a 
rigid  frame,  the  gas  bag  depending  upon  its  inflation  to  maintain  its  form. 

Single-Surfaced  Plane.     Having  fabric  on  upper  side  of  ribs  only. 

Skid.     See  Runner. 

Skidding.  Tendency  of  an  aeroplane  to  make  leeway  or  "slide  off"  in  round- 
ing a  turn  when  not  properly  banked. 

Skin  Friction.  The  resistance  set  up  by  a  moving  surface,  such  as  that  of 
the  supporting  planes  or  propeller  blades. 

Slip.  The  reaction  of  a  propeller  on  the  air,  by  which  it  is  enabled  to  create 
thrust. 

Soaring  Flight.     Gliding  flight  in  an  upward  direction. 

Speed,  Peripheral.     See  Peripheral  Speed. 

Stabilizer.     A  surface  for  automatically  maintaining  balance. 

Stabilizing  Fin.     A  vertical  auxiliary  surface  to  give  lateral  stability. 

Starting  Rail.  The  rail  upon  which  an  aeroplane  is  run  to  give  the  initial 
velocity  necessary  for  starting.  Obsolete. 

Strata.     Well-defined  layers  of  moving  air  or  wind. 

Stream  Lines.  Easy  curves  from  head  to  tail  of  a  dirigible  or  aeroplane,  as  in 
the  pisciform  shape,  which  minimizes  head  resistance. 

Striae.  Literally  "streaks"  in  the  wind;  i.e.,  narrow  strata  moving  at  a  differ- 
ent speed  or  different  direction  to  the  surrounding  air. 

Struts.     Vertical  supporting  members  between  the  main  planes  of  a  biplane. 

Supplementary  Surface.  A  surface  which  is  small  compared  with  the  main 
surfaces  of  an  aeroplane  for  steering  or  balancing. 

Sustaining  Surface.  A  horizontal  surface  for  the  purpose  of  maintaining  a 
horizontal  position;  the  main  plane. 


759 


GLOSSARY 


Tail.     The  rear  part  of  a  flying  machine  to  improve  its  stability  and  afford 

attachments  for  rudders  and  stabilizers. 

Tangential.     The  forward  inclination  of  the  lifting  force  under  certain  con- 
ditions, such  that  the  surfaces  tend  to  advance  into  the  wind. 
Thrust,  Dynamic.     The  work  done  by  the  propeller  in  forcing  the  aeroplane 

ahead.     It  equals  the  weight  of   the  mass  of  air  acted  upon  per  second 

times  the  slip  velocity  in  feet  per  second. 
Thrust,  Static.     The  work  done  by  the  propeller  when  forcing  a  column  of 

air  backward,  the  machine  being  stationary. 
Tractor  Screw.     A  propeller  placed  forward  to  draw  the  aeroplane  after  it, 

in  contrast  with  a  propulsive  screw  which  forces  it  ahead. 
Trailing  Edge.     Rear  edge  of  a  plane  in  its  direction  of  travel. 
Triangulation.     A  method  of  ascertaining  the  height  of  an  object  by  sighting 

from  two  points  on  a  base  line  to  obtain  two  angles  of  an  imaginary  triangle. 

Already  obsolete  in  aeronautics. 

Triplane.     An  aeroplane  having  three  superposed  supporting  surfaces. 
True-Screw  Propeller.     A  propeller  in  which  the  pitch  is  uniform,  as  in  a 

metal  screw  thread.     See  Pitch,  Variable. 

u 

Uniform  Pitch.  A  changing  angle  of  blade  surface  from  hub  to  tip  of  a  pro- 
peller such  that  all  portions  of  the  propeller  blade  tend  to  advance 
through  the  air  at  the  same  speed. 


Vertical  Component.  Amount  of  force  exerted  in  a  vertical  direction  and 
tending  to  lift  the  aeroplane. 

Vertical  Rudder.     An  upright  rudder  for  horizontal  guiding. 

Volplane  (French).  To  glide  down  from  a  height  in  an  aeroplane  with  the 
motor  stopped. 

Vortex.  A  whirling  column  or  spiral  of  air,  usually  ascending,  due  to  tempera- 
ture differences. 

w 

Whirling  Table.     A    device   for   testing   planes   and   propellers   by   revolving 

them  through  the  air. 
Wind  Tunnel.     A  large  tube,  used  for  experimenting  with  surfaces  and  models 

and  so  called  because  a  current  of  air  or  wind  is  artificially  created  in  it. 
Wing  Skid.     A  small  skid  under  the  tip  of  the  wing  to  keep  it  from  contact 

with  the  ground. 
Wing  Wheel.     A  small  wheel  under  the  end   of   the  wing  to  keep  it  from 

contact  with  the  ground. 


760 


INDEX 


INDEX 


The  page  numbers  of  this  volume  will  be  found  at  the  bottom  of  the  pages; 
the  numbers  at  the  top  refer  only  to  the  section. 


Accidents  and  their  lessons 
biplane  vs.  monoplane 
breakage  of  parts  of  aeroplanes 
causes 

dirigible  accidents 
excessive  lightness  of  machines 
failure  of  control  mechanism 
fatal  accidents 
increment  of  speed  in  driving 
lack  of  sufficient  motor  control 
landings 

methods  of  making  tests 
obstructions 


Page 

672 
684 
682 
677 
696 
687 
682 
674 
695 
690 
688 
694 
677 


parachute  garment  as  safeguard  690 

press  reports 

record  breaking 

stopping  of  motor 

study  of  stresses  in  fancy  flying 
Aerial  Experiment  Association 

June  Bug 

Red  Wing  / 

Silver  Dart 

White  Wing 
Aerial  propeller 

blades 

factors  in  propeller  action 

location  of  propellers 

number  of  propellers 

power  of 

propeller  construction 

propeller  design 

propeller  efficiency 

propeller  tests 
Aerodynamic  Institute  of  Kutchino 

propeller  experiments 

Note. — For  page  numbers  see  foot  of  pages. 


672 
686 
681 
691 
126 
128 
127 
129 
127 

411-442 
421 
411 
439 
437 
418 
426 
430 
440 
434 
175 
175 


Page 

Aeronautical  motor  345-410 

American     motor     types     (see 
"American  motor 

types")  363 

early  types  345 

foreign  motor  types  (see  "For- 
eign motor  types")         379 
general  motor  requirements  347 

Aeronautical  practice  443-566 

altitude  and  its  measurement       482 
automatic  stability  455 

legal  status  of  the  art  505 

military    importance    of    aero- 
plane and  dirigible          527 
stability  of  aeroplane  443 

wireless  telegraphy  in  aeronau- 
tics 551 
Aeronautics,  wireless  telegraphy  in     551 
Aeroplanes 

building  and  flying  (see  "Build- 
ing and  flying  an  aero- 
plane")   "  567-703 
efficiency  of  273 
with  fixed  stabilizing  planes         318 
Baldwin  biplane  321 
Herring  biplane  318 
Waldon  Dyett  monoplane    321 
management  of  121 
maneuvers  in  United  States         541 
actual  war  scouting                546 
bomb    dropping    perform- 
ance                                   544 
Curtiss  and  his  hydroaero- 
plane                                546 
Ely  in  San  Francisco  Har- 
bor                                   543 


761 


INDEX 


Page 
Aeroplanes 

maneuvers  in  United  States 

scouting  operations  545 

military  importance  of  527 

models  568 
special     types      (see     "Special 

Types  of  Aeroplanes")  275 
standard  types  (see  "Standard 

types  of  aeroplanes")  197 
types  of  (see    "Types  of  aero- 
planes")                    197-344 

Air  harbors  717 

Air  holes  148 

Air  pilots  716 

Air  reaction  principle  456 

longitudinal  stability  control  457 

Wright  Brothers'  patent  458 

Akron  72 

inflating  79 

substitute  for  the  equilibrator  75 

wire-wound  fabric  78 

Albatross  biplane  301 

Altitude  and  its  measurement  482 

acoustic  method  490 

altitude  records  482 

barograph  492 

captive  balloon  method  485 

individual  barograph  records  498 

Johnstone  498 

Drexel  499 

Legagneux  500 

methods  of  485 

summary  of  altitude  records  500 

triangulation  487 

Altitude  records                              482,  500 

Amateur  aviators  698 

classes  of  699 

inventors  699 

would-be  performers  700 

Wright  and  Curtiss  patents  700 

"America"  59 

accessories  67 

motive  power  65 

type  of  construction  61 

American  dirigibles  58 

Akron  72 

America  59 

Note. — For  page  numbers  see  foot  of  pages. 


Page 
American  dirigibles 

United  States  war  bafioon  58 

wire-wound  fabric  78 

American  experimental  research  193 

Curtiss  laboratory  93 

American  motor  types  363 

Curtiss  366 

eight-cylinder  V-type  371 

Hamilton  372 

Hendee  371 

four-cylinder  water-cooled  type  368 

Harriman  368 

horizontal  opposed  type  368 

Call  369 

Detroit  aero  369 

rotary  type  373 

Ada*ms-Farwell  373 

Brooke  "Non-Gyro"  motor  376 

Metz  377 

Weinberg  377 

two-cycle  motors  372 

Elbridge  373 

Fox  373 

Roberts  372 

weight  per  horse-power  hour  378 

Wright  363 

Antoinette  armored  monoDlane  285 

Antoinette  monoplane  238 

Art  of  flying  653 

aeroplane  in  flight  657 

center  of  gravity  657 

center  of  pressure  660 

first  flight  661 

ground  practice  660 

making  turn  663 

methods  used  in  aviation  schools  654 

planning  a  flight  670 

starting  and  landing  670 

training  the  professional  aviator    671 

turning  in  a  wind  669 

use  of  elevating  plane  656 

warping  the  wings  662 

Aspect  ratio  138,  262 

Aspiration  172 

Automatic  stability  455 

air  reaction  principle  456 

Doutre  stabilizer  477 


762 


INDEX 


Page 
Automatic  stability 

Ellsworth  lateral  stabilizer  480 

Eteve  stabilizer  465 

gravity  principle  460 

gyroscopic  stabilizers  468 

Aviation,  early  days  of  99 

Aerial  Experiment  Association  126 

Herring-Curt iss  Company  129 

historical  99 

Cayley  99 

Henson  100 

Langley  101 

Maxim  102 

miscellaneous  101 

Langley's  experiments  104 

United      States      Government 

requirements  122 

Wright  (Wilbur)  in  Europe  124 

Wright  Brothers'  experiments  107 
Aviation,    theory    of    (see    "Theory 

of  aviation")  99-196 

Aviation  and  its  future  705-752 

aviation  records  732 

dirigible  vs.  aeroplane  705 

flying  machine  of  the  future  740 

rewards  of  aviation  720 

Aviation  records  732 

early  records  733 

records  for  1909  and  1910  735 

records  for  1911  735 

Aviation  rewards  720 

Aviators,  amateur  698 


Bl 


IS 
583 
684 


Balloonets,  functions  of 
Biplane,  building  a  Curtiss 
Biplane  vs.  monoplane 
Blades 

area 

contour 

fabric-covered 

flexible  type 

number 
Bleriot  Canard 
Blcriot  limousine 
Bleriot  XI  monoplane 
Bleriot  XII  monoplane 

Note. — For  page  numbers  see  foot  of  pages. 


424 

424 
425 
425 
422 

284 
282 
247 
250 


Page 
Bleriot    monoplane    (see    "Building 

a  Bleriot")  623 

Bleriot  racer  284 

Breguet  biplane  301 

British  dirigibles  57 

Brown  hydroaeroplane  337 

Brucker's   proposed   expedition  89 

motive  power  92 

novel  features  91 

type  of  balloon  90 

Building  aeroplane  models  568 

model  with  gasoline  motor  574 

model  with  rubber-band  motor  568 

Building  a  Bleriot  monoplane  623 

control  system  642 

covering  planes  647 

fuselage  626 

installation  of  motor  649 

motor  623 

new  features  650 

running  gear  630 

truss  frame  built  on  fuselage  629 

wings  638 

Building  a  Curtiss  biplane  583 

ailerons   for   lateral   stability  606 

assembling  biplane  617 

controls  615 

cost  583 

covering  of  planes  606 

general  specifications  584 

main  planes  and  struts  594 

making  propeller  607 

making    turnbuckles    for    truss 

wires  596 

mounting  engine  614 

outriggers  599 

running  gear  597 

tests  617 

Building  a  glider  577 

glider  with  rudder  and  elevator  581 

learning  to  glide  581 

main  frame  577 
Building  and  flying  an  aeroplane  567-703 

accidents  and  their  lessons  672 

amateur  aviators  698 

art  of  flying  653 

building  aeroplane  models  568 


763 


INDEX 


Page 
Building  and  flying  an  aeroplane 

building  a  Bleriot  monoplane     623 

building  a  Curtiss  biplane  583 

building  a  glider  577 

Burgess  hydroaeroplane  336 


Clement-Bayard  II  33 

Cody  biplane  235 

Curtiss    biplane    (see    "Building    a 

Curtiss")  214,  684 

Curtiss  racing  machine  306 

Curtiss  hydroaeroplane  328 

combination    land    and    water 

type  335 

Curtiss  family  hydroaeroplane    336 

naval  trials  with  improved  type  332 

Curtiss  motor  366 


DeMarcay-Mooney  monoplane  291 
Deperdussin  monoplane  303 
Detroit  Flying  Fish  338 
Dirigible,  achievements  of  82 
Brucker's   proposed   expedition     89 
carrying  passengers  by  airship     92 
Deutschland  92 
Zeppelin  VI  94 
miscellaneous  exploits  95 
Wellman's  expedition  82 
Dirigible  vs.  aeroplane  705 
aeroplane  709 
behavior  in  a  wind  711 
cost  709 
passenger  service  710 
portability  711 
speed  710 
strategic  advantages  710 
air  harbors  717 
air  pilots  716 
dirigible  705 
improvements  of  design  719 
large  radius  of  action  709 
recent    developments    in    diri- 
gibles 713 
refinement  of  details  715 

Note. — For  page  numbers  see  foot  of  pages. 


Page 

Dirigible  balloons  1-97 
achievements  of  the  dirigible         82 

American  dirigibles  58 

British  dirigibles  57 

classification  2 

early  attempts  1 

early  dirigibles  6 

first  flying  machines  2 

French  dirigibles  30 

German  dirigibles  38 

problems  of  the  dirigible  8 

simple  balloons  3 

Dirigible,  problems  of  8 

ability  to  float  8 

critical  size  of  bag  12 

dynamic  equilibrium  17 

fabric  and  color  14 

function  of  balloonets  18 

location  of  propeller  23 

longitudinal  stability  15 
relations  of  speed  and  radius  of 

travel  25 

static  equilibrium  14 

Doutre  stabilizer  477 

Dunne  biplane  288 

Dynamic  equilibrium  17 


Early  dirigibles  6 
Eddies  and  waves,   effect  of  149 
Efficiency  of  aeroplane  273 
Eiffel    Aerodynamometric    Labora- 
tory 180 
wind  pressure  experiments  180 
Elementary  aerodynamics  130 
air  pressure  133 
curved  surfaces  134 
on  moving  surfaces  133 
plane  surfaces  133 
air  resistance  130 
aspect  ratio  138 
center  of  pressure  140 
evolution  of  curved  supporting 

surface  141 

ratio  of  lift  to  drift  136 

skin  friction  140 

Ellsworth  lateral  stabilizer  480 


764 


INDEX 


Page 

Eteve  stabilizer  465 

Etrich  bird-wing  monoplane  295 

F 

Fabre  hydroaeroplane  324 

Fairchild  monoplane  314 

Farman  biplane  227 

Farman'(H)  monoplane  317 

First  balloon  4 

First  flying  machine  2 

First  Lebaudy  30 

Flight  270 

Flying,  art  of  653 

Flying  machine  of  the  future  740 

duplicate  power  plant  752 

improvements  in  construction  745 

monoplane  vs.  biplane  745 

racing  machine  of  the  future  748 

reefed  supporting  surfaces  750 

unpromising  types  740 

helicopter  741 

miscellaneous  744 

ornithopter  740 

Foreign  motor  types  379 

conventional  four-cylinder  type  381 

Wright-Barriquand  381 

other      vertical      cylinder 

types  383 
Panhard        and        Primi- 

Berthand  382 

Vivinus  382 

fan  and  star  types  396 

Anzani              (  396 

Clement  403 

Farcot  399 

M.  A.  B.  397 

Pelterie  404 

Gnome  revolving-cylinder  type  408 

Gobron-Brille  X-form  406 

horizontal-opposed  type  379 

Clement  381 

Darracq  380 

Deuthil-Chalmers  379 

V-type  389 

Antoinette  389 

Fiat  393 

Pipe  395 

Note. — For  page  numbers  see  foot  of  pages. 


Foreign  motor  types 

V-type 

Renault 

water-cooled  types 
French  dirigibles 

Astratorres 

Clement-Bayard  II 

first  Lebaudy 

La  Patrie 

La  Republique 

Lebaudy  1904 

Le  Jaune 

Le  Temps 


Page 


394 
396 
30 
36 
33 
30 
31 
31 
30 
31 
36 


Lieutenant  Selle  de  Beauchamp    37 

Zodiac  36 

G 

German  dirigibles  38 
Gross  53 
Krell  I  53 
Parseval  49 
Veeh  I  55 
Zeppelin  38 
Glider,  building  a  577 
Gliding  and  soaring  153 
aspiration  172 
conditions  for  continuous  soar- 
ing 167 
ascending  winds  168 
horizontal  winds  168 
horizontal  winds  of  pulsat- 
ing character  169 
early  observations  162 
Andrews  162 
historical  records  164 
Montgomery's    gliding    experi- 
ments 159 
new  Wright  glider  154 
theory  of  soaring  166 
Glossary  753-761 
Grade  monoplane  251 
Gross  53 
Gyroscopic  stabilizers  468 
Beach  device  474 
gyroscope  action  469 
Regnard  device  470 
true   stabilizer   independent   of 

wind  changes  468 


765 


6 


INDEX 


Page 
H 

Hanriot  monoplane  305 

Helicopter  741 

Herring-Curtiss  Company  129 

Hydroaeroplanes  322 

advantages  322 

Brown  337 

Burgess  336 

Curtiss  328 

Detroit  Flying  Fish  338 

early  attempts  323 

Fabre  324 

Transatlantic  339 

I 

Incident  angle  263 
Inflating    "Akron"  79 
Internal  work  of  wind  143 
air  holes  148 
certain  effects  on  wind  151 
character  of  air  currents  143 
effect  of  eddies  and  waves  149 
movements  of  plane  in  wind  143 
behavior  in  pulsating  wind  145 
soaring  146 
with  vertical  guides  143 
relative  speed  of  wind  and  aero- 
plane 150 
Italian  airship  operations  547 


K 


June  Bug 

Keels 

Kodophone 
Krell  I 


Langley's  experiments 
La  Patrie 
La  Republique 
Lebaudy  1904 
Legal  status  of  art 

customs 

legislation 

Wright    patents    in    American 
and  foreign  courts 


128 


267 
96 
53 

104 

31 

31 

30 

505 

526 

524 

505 


Legislation 

Le  Jaune 

Lieutenant   Selle   de   Beauchamp 

Longitudinal  stability 

M 


Page 

524 

31 

37 

15 


Meusnier,    the    pioneer    dirigible  6 

Military    importance    of    aeroplane 

and  dirigible  527 

adaptability  to  war  531 

aeroplane  maneuvers  in  United 

States  541 

attitude  of  military  powers          527 

guns  for  aerial  warfare  547 

Italian  operations  547 

operations  in  France  535 

military  aeroplane  tests         538 

military  maneuvers  535 

Military  powers,  attitude  of  527 

Modern  aerodynamic  research  174 

Aerodynamic        Institute        of 

Kutchino  175 

American  experimental  research  193 
Eiffel  Aerodynamometric  Lab- 
oratory 180 
methods    of    experimenting    on 

test  surfaces  190 

pressure  measuring  methods         192 
results   of   research   in   various 

laboratories  187 

Montgomery's  gliding  experiments     159 
Morane  monoplane  302 

Motor,  automobile  vs.  aeronautical    348 
Motor,  stopping  of  681 

Motor  requirements  347 

automobile      vs.      aeronautical 

motor  348 

fundamental  features  of  design     349 
automatically    -    operated 

inlet  valves  351 

cost  no  object  350 

low  weight  per  horse-power  350 
short  stroke  349 

standard  forms  352 

Motor  types  (see  "American  motor 
types"  and  "Foreign 
motor  types")  363,  379 


Note. — For  page  numbers  see  foot  of  pages. 


766 


INDEX 


Mounting 
Multiplanes 
Maxim 
Paulhan 
Roe 
Sellers 
Zerber 


N 


Nieuport  monoplane 
Nomenclature 


Ornithopter 


Parseval 

Paulhan  trussed  type  of  aeroplane 

Pelterie  monoplane 

Pendulum  devices,  objections  to 

Pfitzner  monoplane 

Pressure,  center  of 

Prizes 

for  flights 

for  improvements 
Propeller 

location  on  aeroplane 

location  on  dirigible 
Propeller  action,  factors  in 

diameter 

peripheral  speed 

pitch 

pitch  ratio 

slip 

thrust 
Propeller  construction 

American  methods 

Chauviere  method 

Hollands 

material 

standard 
Propeller  design 

true-screw  type 

variable-pitch  type 
Propeller  efficiency 
Propeller  tests 

British 


Page 
267 
308 
311 
311 
309 
311 
311 


278 
198 


740 


49 
275 
255 
463 
257 
140 

721 
731 
23 
439 
264 
411 
415 
416 
411 
415 
412 
413 
426 
429 
428 
430 
426 
427 
430 
430 
433 
440 
434 
437 


Page 
Propeller  tests 

Herring  434 

Kutchino  laboratory  175 

Q 

Queen-Martin  biplane  298 

R 

Racing  machine  of  the  future  748 

Records  of  aviation  732 

Red  Wing  127 

Rewards  of  aviation  720 

prizes  for  flights  721 

prizes  for  improvements  731 

Rozier  5 

Rudders  265 

S 

Santos-Dumont  monoplane  242 

Short  two-motor  biplane  287 

Silver  Dart  biplane  129 

Simple  balloons  3 

balloon,  success  of  5 

first  balloon  4 

improvements  by  Charles  5 

Rozier  5 

theory  3 

Skin  friction  140 

Soaring,  theory  of  166 

Sommer  biplane  231 

Special  types  of  aeroplanes  275 

Albatross  biplane  301 

Antoinette  armored  monoplane  285 

Bleriot  Canard  284 

Bleriot  limousine  282 

Bleriot  racer  284 

Breguet  biplane  301 

Curtiss  racing  machine  306 

De  Marcay-Mooney  monoplane  291 

Deperdussin  monoplane  303 

Dunne  biplane  288 

Etrich  bird-wing  monoplane        295 

Fairchild  monoplane  314 

Farman  monoplane  317 

Hanriot  monoplane  305 

Morane  monoplane  302 

multiplanes  308 


Note. — For  page  numbers  see  foot  of  pages. 


767 


INDEX 


Page 
Special  types  of  aeroplanes 

Nieuport  monoplane  278 

Paulhan  trussed  type  275 

Queen-Martin  biplane  298 

steel  tube  construction  314 

short  two-motor  biplane  287 

Tatin-Paulhan  aerial  torpedo  283 
Tubavion  monoplane  302 

types     with     fixed     stabilizing 

plane  318 

Valkyrie  monoplane  305 

variable  speed  aeroplanes  292 

Speed  and  radius  of  travel,  relations 

of  25 

influence  of  wind  27 

total    weight    per    horsepower 

hour  25 

Stability  of  aeroplane  443 

conditions  for  stability  444 

longitudinal  and  lateral  stability  453 
methods  of  increasing  stability  445 
methods  of  producing  effective 

damping  couple  448 

study   of   "center  of  pressure" 

curves 

variations  of  center  of  pressure 
Stabilizers 


D  outre 
Ellsworth 
Eteve 
gyroscopic 

Standard  types  of  aeroplanes 
biplanes 

Cody 

Curtiss 

Farman 

Sommer 

Voisin 

Voisin  tractor  screw 

Wright 

Wright  Model  B 

Wright  racer 
comparison  of 

aspect  ratio 

efficiency 

flight 

incident  angle 


450 
443 
460 
477 
480 
465 
468 
197 
199 
235 
214 
227 
231 
219 
223 
199 
206 
204 
260 
262 
273 
270 
263 


Page 

Standard  types  of  aeroplanes 
comparison  of 

keels  267 

mounting  267 

propellers  264 

rudders  265 

transverse  control  261 

general  survey  197 

monoplanes  238 

Antoinette  238 

Bleriot  XI  247 

Bleriot  XII  250 

Grade  251 

Peltcrie  255 

Pfitzncr  257 

Santos-Dumont  242 

nomenclature  198 

Static  equilibrium  14 

Steel  tube  construction  314 


Tables 

aeroplane   altitude   records   for 

1910  500 

aeroplane  records  for  1909  and 

1910  734 

centripetal  force  acting  on  aero- 
plane at  various  speeds 
and  curvatures  in 
flight  693 

characteristics  of  different  types  272 
fall  of   barometer    at    different 
elevations     above    sea 
level  493 

fatal  aeroplane  accidents  675 

minimum  change  of  level  neces- 
sary to  produce  vari- 
ous speed  increments     696 
propeller  blade  date  610 

relative  strength  of  clear  spruce 

and  elm  587 

speed  data  271 

speed   of   wind   for   vicinity   of 

Paris  28 

Tatin-Paulhan  aerial  torpedo  283 

Theory  of  aviation  99-196 

early  days  of  aviation  99 


Note. — For  page  numbers  see  foot  of  pages. 


768 


INDEX 


Page 
Theory  of  aviation 

elementary  aerodynamics  130 

gliding  and  soaring  153 

internal  work  of  wind  143 

modern  aerodynamic  research  174 

Transatlantic  hydroaeroplane  339 

probable  features  of  design  341 

Transverse  control  261 

Tubavion  monoplane  302 

Types  of  aeroplanes  197-344 

hydroaeroplanes  322 

special  types  275 

standard  types  197 

U 

United  States  Government  require- 
ments 122 
fulfilled  124 
tests  of  1908  123 

United  States  war  balloon  58 

V 

Valkyrie  monoplane  305 

Variable  speed  aeroplanes  292 

Breguet  293 

Capon  294 

Reister-Picard  294 

Veeh  I  55 

Voisin  biplane  219 

Voisin  tractor  screw  223 

W 

War  balloon  58 

Wellman's  expedition  82 

White  Wing  biplane^  127 

Wind,  internal  work  of  143 
Wind  and  aeroplane,  relative  speed 

of  150 

Wind  pressure  experiments  180 

Wireless  telegraphy  in  aeronautics  551 

dangers  from  electric  discharge  553 

early  experiment  on  balloons  551 

first  message  557 

general  problems  562 

Akron  outfit  565 

eliminating  noise  562 

forms  of  aerial  563 

possible  developments  564 

Note. — For  page  numbers  see  foot  of  pages. 


Page 

Wireless  tejegraphy  in  aeronautics 
general  problems 

use  of  visible  signals  563 
Horton's  experiments  558 
preventive  methods  554 
recent  records  559 
Beck  560 
Lorraine  559 
McCurdy  560 
wireless  on  aeroplanes  557 
wireless  on  dirigibles  551 
wireless  on  the  Zeppelins  556 
Wright  (Wilbur)  in  Europe  124 
Wright  biplane  199 
Wright  glider  154 
glider  sustained  without  appar- 
ent motion  156 
gliding  nights  at  Kitty  Hawk  155 
lift  and  drift  ratio  157 
Wright  Model  B  206 
Wright  motor  363 
Wright  patents  505 
Wright  racer  204 
Wright  Brothers'  experiments  107 
balancing  methods  109 
first  power  flight  117 
gliding  experiments  113 
management  of  an  aeroplane  121 
propeller  design  117 
verification    of    pressure     con- 
stants 114 
working  the  planes  110 
Wright  and  Curtiss  patents  700 
evasion  by  acquiring  European 

types  702 
evasion    by    invention    of    new 

types  700 


Zeppelin  airships  38 

construction  38 

Deutschland  I  and  II  44 

first  trials  40 

longest  airship  flight  42 

Schwaben  45 

second  airship  40 

Zodiac  36 


769 


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